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CHAPTER 1

AN EVOLVING THREAT

Unlike surface gunnery, anti-aircraft gunnery developed in the context of a rapidly-changing threat. There were also changes in the way in which navies evaluated the air, compared (say) to the surface, threat. There was already an air threat in 1917–18. The Germans and the British both used torpedo bombers in combat, and the British considered reconnaissance Zeppelins a major problem in the North Sea.¹ Aircraft were prominent enough in anti-submarine warfare that some submarines were given heavy anti-aircraft guns. When the Royal Navy reviewed the situation in 1931–3, its Naval Anti-Aircraft Gunnery Committee cited the rise of ship-based aircraft in the US, British and Japanese navies, French flying boat operations over the Mediterranean, and the impressive mass Italian long-range flights (mainly led by Italo Balbo: the formations were often called ‘Balbos’).

Air Arms

The US Navy and the Imperial Japanese Navy both had their own air arms during the inter-war period. The US Navy became particularly air-minded. It created an instant corps of senior naval aviators by requiring all commanders of naval aviation activities and ships (including carriers) to have either ‘wings’ or aviation observer status. Ambitious officers sought the necessary training and gained an aviation perspective. The United States also created a large naval air arm, which it demonstrated to itself in the annual Fleet Problems (fleet exercises) in the Pacific. The Fleet Problems and also nearly compulsory senior officer education at the Naval War College (where the students worked out phases of the war plan against Japan) educated even non-aviators in the impact of naval aviation. For example, after one Fleet Problem in the late 1930s, the main complaint of the battleship officers was that the carriers had fought what seemed to be a private war, denying them the air services, including fighter cover, they wanted. Rear Admiral Ernest J King (Commander, Air Squadrons, Battle Force and later wartime Chief of Naval Operations) pointed out that the carriers could easily destroy each other. If they did not fight their ‘private war’, the battleships would never have any air services, because all the aircraft would be on the bottom. Typically US carriers operated well away from the battle line, which was easily spotted at a distance, in order to make it more difficult for enemy scouts to find them. That contrasted sharply with contemporary British thinking. King’s insight, which probably was widely understood, emphasised the need for anti-aircraft weapons, because at times the fleet would have to defend itself.

In support of the carrier vs. carrier war, in the late 1930s the US Navy decided that its dive bombers would have an alternative role as scouts; they were therefore designated in an SB series, as in the SBD Dauntless. US carriers typically had four squadrons on board: one of fighters, one of dive bombers, one of scouts, and one of torpedo bombers. Until the advent of radar, there was little hope that the fighters could effectively protect the carriers, which operated singly. The fighters were intended more as strike support, helping the strike aircraft deal with any defending fighters and probably also helping by strafing enemy air defence control and guns.

The pre-war Imperial Japanese Navy also had a large carrier force. Unlike the US Navy, the Japanese followed the Royal Navy (see below) in equating carrier aircraft capacity with hangar capacity.² Typically their carriers had three rather than four squadrons on board. That is why the three US carriers at Midway had about as many aircraft as the four Japanese carriers they faced and defeated. On the other hand, in 1940–1 the Japanese succeeded in creating multi-carrier Air Fleets which could fight as single entities. Overall, they had little faith in air defence: the enemy carriers had to be destroyed before they could strike. The Japanese depended mainly on fighters rather than on shipboard anti-aircraft guns for fleet defence. However, they appear not to have appreciated the importance of fighter control, e.g. to keep fighters from being drawn entirely to counter one raid while another might be approaching. For them, Midway was an object lesson in just such failure: the defending fighters were drawn down to deal with the US torpedo bombers leaving the way open for the dive bombers. Without radar and also with poor voice radio, fighter control was impossible.

The Mitsubishi G3M (‘Nell’) made up the bulk of the Imperial Japanese Navy’s considerable land-based bomber force when the Pacific War began, and this bomber also made up the majority of the force which sank Prince of Wales and Repulse. The object under the belly of this ‘Nell’ is the rack for a torpedo or bombs. (Phil Jarrett)

The most important factor in air operations against ships is that the sea is so broad. Air attacks cannot be mounted until the enemy is found. That is why signals intelligence was so important in the Second World War: when it worked, it showed the attacker where to search. Operations in narrow waters were of course simpler, but they always required search before attack. The Japanese used shipboard floatplanes to find enemy fleets. In 1942 the Japanese naval staff tried an alternative, the high-performance carrier aircraft shown here. This C6N1 Saiun (‘Myrt’) was designed to a Spring 1942 specification requiring a maximum speed of 350kts and a range of 1500nm at 210kts (maximum 2500nm). The Saiun flew in May 1943 and was accepted even though it did not achieve the desired speed. During the battle of the Philippine Sea, Saiuns effectively shadowed the US fleet, their high speed protecting them from interception. They were responsible for the great success the Japanese enjoyed: they were able to attack from well beyond the attack range of the US fleet. That did them little good, because US fighter control and US anti-aircraft guns were so effective. This ‘Myrt’ was captured on Saipan in June 1944.

The wartime successor to ‘Nell’ was the G4M (‘Betty’), which, like its predecessor, could deliver both bombs and torpedoes. G4Ms were part of the attack against Repulse and Prince of Wales, and later in the war they executed effective night torpedo attacks against US carriers and cruisers. At the end of the war they launched Okha manned stand-off missiles. (Philip Jarrett)

Like their US counterparts, Japanese cruisers carried floatplanes assigned to scouting as well as spotting duties. In the US Navy, the floatplane scouts were intended for use when the cruiser or cruisers operated independently, far from the fleet. Unlike the US Navy, the Japanese used these same floatplanes to scout for carriers screened by the cruisers, as at Midway. Wartime US and British observers considered that the problems of tracking enemy fleet units and of coaching a strike force into position had received particular attention in the Imperial Japanese Navy.³ Scouting was considered so important that, unlike the US Navy, the Japanese separated it from strike, to the extent that scouts were ordered to avoid combat if possible so that they could complete their scouting missions. The fleet scouting mission was symbolised by the design of the Tone class cruisers, with their open aircraft areas aft. Only during the war did the Japanese develop a specialised high-performance carrier scout, the C6N1 Saiun.⁴ It had no Western equivalent. Wartime Japanese air tactics envisaged a scout or snooper working with a strike force, using elaborate tracking and liaison techniques. By 1943–4 Japanese scouting aircraft had radar. They were advised to minimise both radar and radio transmissions until the moment came to home the strike force on the target, at which time there had to be a considerable volume of traffic to and from the tracking aircraft. On this basis communications volume became a reasonable indication that a striking force or a relief shadower was being homed on the target.

Japan was unique in having both a carrier air arm and a substantial naval land-based air arm. The US Navy also had a large shore-based air arm, but it consisted of flying boats, not high-performance bombers like the G3M ‘Nell’ and its successor G4M (‘Betty’). ‘Nell’ was built to a requirement conceived in 1933 by Admiral Yamamoto, who was then chief of the technical division of the Japanese Naval Bureau of Aeronautics (the equivalent of the US Navy’s BuAer). Admiral Yamamoto was aware of developments which gave twin-engine aircraft very high performance (which in Britain was taken to mean that ‘the bomber will always get through’) and he asked for an aircraft capable of maintaining surveillance over Pearl Harbor, the US fleet base, from Japanese airfields. Such surveillance was necessary if, as the Japanese hoped, they could intercept and defeat the US fleet before it reached their home waters. The aircraft also had to be capable of carrying out attacks at long range. Yamamoto and others were interested in using a force of land-based bombers which could shuttle among the Micronesian islands Japan then ruled as League of Nations mandates. It was clear that the flying boats Japan was using at the time lacked the requisite performance.⁵ The requirement was in accord with the Japanese naval strategy of wearing down an approaching US fleet before it encountered the main Japanese fleet, and the high performance envisaged would give the new bomber a reasonable degree of immunity against the fleet’s fighters. Yamamoto chose Mitsubishi as sole-source developer because that company had imported engineers from the German company Junkers (which was building high-performance twin-engine bombers) specifically to obtain the technology involved. In effect ‘Nell’ was the air power equivalent of the Yamato class battleship: a technological solution to the numerical inferiority of the Japanese battle fleet. The ‘Nell’ entered production in June 1936. As the longest-range Japanese bomber, it participated in the war against China that began in 1937, first carrying out attacks from Formosa in August. These operations made the British aware of it, though not of its extraordinary range. It also appears that the British tended to mirror-image, and thus to associate all land-based bombers (such as G3M) with the Japanese army, not the navy. That may have blinded them to the threat of such aircraft (in 1942 US air intelligence was counting Japanese biplane torpedo bombers as the aircraft which sank the two British capital ships).

The Heinkel He 111H-6 was the main German wartime land-based torpedo bomber, typically carrying two torpedoes (in this case practice F-5bs) as shown. Numbers were always limited, and it lacked radar. This aircraft was used mainly against Russian convoys, from 1942 onwards. (Philip Jarrett)

The longest-ranged German anti-ship aircraft was the Fw 200 Condor, used both for direct attack and for reconnaissance in support of U-boats. (Philip Jarrett)

Japanese land-based units (including seaplanes) were organised into Air Groups named after the cities at which they were based. In 1940 the Japanese created an 11th Air Fleet of medium bombers. It consisted of three Air Flotillas, each of which consisted of two or three Air Groups. In effect it was the land-based equivalent of the First Air Fleet, the carriers and their aircraft separate from the First Fleet (which included two carriers supporting the battleships directly). There were also fleets intended specifically to operate in the Mandated Islands: the Fourth and Fifth. Among their roles were attrition of any US force trying to pass through the Mandates en route to the expected decisive battle in home waters. Fourth Fleet included 24th Air Flotilla, equivalent to the three medium bomber flotillas (21st, 22nd, 23rd) of 11th Air Fleet. In addition to the attacks on the two British capital ships, aircraft of the 21st and 23rd Air Flotillas were responsible for the early attacks on the US air bases in the Philippines.

The French Navy had both a few carrier aircraft and considerable numbers of land-based torpedo bombers as well as seaplanes. Its aircraft do not figure in this book because it had few opportunities for action before France fell in 1940.

Before the war Germany had a separate naval air arm equipped with ship-based floatplanes and with larger He 115 coastal floatplanes and flying boats.⁶ Despite an agreement leaving attacks against ships to the naval air arm, the Luftwaffe created its own anti-ship unit, X Fliegerkorps, which soon absorbed the few land-based units the navy had formed. At the outbreak of war the Luftwaffe considered the torpedo inadequate compared to bombing, particularly dive or glide bombing. Torpedo attack was frowned upon as tactically difficult. In November 1940 Göring extracted from Hitler an order temporarily forbidding the provision of aerial torpedoes to anti-shipping units, in theory to allow their use in a special operation in the Mediterranean (this was soon after the Luftwaffe conducted successful torpedo trials using the He 111). The Luftwaffe did not take over development of air-launched torpedoes until 1942, by which time it was too late to develop new ones for wartime service. German aircraft were used most extensively against merchant ships between 1939 and 1941. According to a post-war study published in the BuAer Confidential Bulletin, during this period Allied losses in ships sunk, captured and severely damaged were about twice that the United States brought into the war in December 1941. In effect the 1939–41 German war on merchant shipping cost the Allies a year of new construction. Apart from mining, which peaked in November 1939, German aircraft did not attack merchant ships during 1939, due both to lack of resources and to deference to neutrals. Systematic attacks on minesweepers began in December, and attacks on merchant ships began with the invasion of the Low Countries in May 1940. During the thirteen months ending 31 May 1941, before German air assets were redirected against the Soviet Union, German aircraft sank or severely damaged 3.8 million tons of merchant ships, compared to 3.2 million for U-boats; the aircraft accounted for 1.7 million tons sunk and 2.1 million tons disabled.

The Germans made extensive use of their longest-range aircraft, Fw 200 Condors (modified pre-war airliners), against merchant ships. Because they could not dive-bomb, like Ju 87s or glide-bomb like Ju 88s, Condors had to make masthead attacks in order to score hits. Before British and other merchant ships could be armed adequately, they were effective: the Germans claimed that in the initial campaign between 15 March and 31 October 1941, bomber attacks accounted for 161 merchant ships sunk (plus one probable) and 113 damaged. This was apart from bomber attacks around the British Isles. As the merchant ships were increasingly armed, these attacks had to be abandoned, initially against convoys and then even against individual ships. Eventually the Condor was modified to attack at high-level using a computing bomb sight. These aircraft were also used for aerial mining around the western ports of the United Kingdom, and eventually to launch stand-off missiles. Their most important role was reconnaissance in support of the U-boat campaign. Success was hampered by the inability of both the U-boats and the aircraft to find their positions accurately, so that a convoy position report might be useless (the wolf packs solved the problem by creating patrol lines of submarines, but that became impossible as Allied air cover improved). The reconnaissance role became crucial after mid-1943, when the Germans lost their ability to read convoy codes. Admiral Karl Dönitz began to seek air support for the U-boat campaign almost upon gaining office as naval chief early in 1943. In February 1943 he signed a memo: air reconnaissance was now crucial. Aircraft had to penetrate to mid-Atlantic, find convoys, shadow them, and lead U-boats to them, because the existing wolf pack tactics of contacting and shadowing convoys (coupled with code-breaking) were proving less and less successful. Reconnaissance was of limited value because aircraft lacked the endurance to search large areas well out in the Atlantic: they could only fly out to a chosen position and return. Without code-breaking, there were no designated convoy positions.

According to the German navy, only in 1941 did the Luftwaffe began to accept that an anti-shipping campaign was the best weapon to use against the United Kingdom, and in the first quarter of that year it shifted its effort to attacks against British coastal targets and shipping west of Ireland. There was also a vigorous and effective aerial mining campaign. Aircraft and U-boats were integrated to an extent to oppose Allied convoys to the Soviet Union. The Germans claimed 25 per cent torpedo hits against convoys PQ16, PQ17 and PQ18. They found that it took far fewer torpedo sorties than dive bomber sorties to sink a ship: 9.8 vs 23.6 against PQ16 and 7 vs 9.2 against PQ17 (best weather for dive bombing), but 7.3 vs 24.3 against PQ18 (worst weather for dive bombing). After the war, German naval officers complained that even when they could be convinced to attack convoys, pilots generally concentrated on the larger ships, which they imagined were the more interesting targets, avoiding the escorts and the smaller, more vulnerable ships; large ones could absorb many hits without sinking.

Like Germany, the United Kingdom had an independent air force, but it also had a Fleet Air Arm which reverted to Admiralty control in 1939. The RAF had long been interested in anti-ship attack, both to defend distant territories and in hopes of supplanting the navy. Both roles made it interested in land-based torpedo bombers. The advent of metal-covered airframes and high-powered engines promised high performance. The Beaufort was the intended successor to the biplane Vickers Vildebeest. One is shown dropping a torpedo. Note the air tail, which is cocked up to keep the torpedo’s tail up. When it began using Beauforts against defended enemy convoys in the Mediterranean, the RAF had to learn to provide defence-suppression aircraft alongside the torpedo bombers. In many cases its resources were so badly stretched that there were few bombers, and they suffered badly. (Philip Jarrett)

The Soviet Union had a substantial naval air arm without carriers. Like the Japanese, it operated land-based bombers and its fighters defended naval bases. The bombers, of the same types operated by the land air force, were organised into Mine-Torpedo Regiments. They were expected to neutralise an enemy fleet by mining his bases and their approaches. This force was not particularly effective during the war, but the Mine-Torpedo Regiments evolved after the war into missile-firing units which the US Navy considered the most serious threat to its carriers. The shore-based naval fighters were absorbed into the Soviet national air defence arm only about 1956.

Wellingtons proved to be effective night torpedo bombers. This aircraft of 38 Squadron is shown in Egypt in 1942. Note the absence of the usual air tail. (Philip Jarrett)

The Beaufighter played several important parts in the war at sea. Initially the Admiralty saw it as long-range fighter capable of covering major fleet units near enemy territory in European waters, much as it thought the Germans were using their long-range fighters to give their own capital ships freedom of action. On this basis the Admiralty convinced the Ministry of Production to keep the Beaufighter in production after the initial RAF night fighter requirement had been met. Coastal Command also wanted Beaufighters, both to protect coastal shipping and as a strike aircraft. In 1942 it began to form Strike Wings consisting of both torpedo Beaufighters (Torbeaus, shown) and anti-flak Beaufighters whose strafing runs were intended to suppress enemy air defences. This combination proved far more successful than the earlier masthead-level attacks. The success may have been due in part to the greater number of attacking aircraft involved, which helped saturate enemy air defences, and also to the relatively high speed of the Beaufighter, which also made defence more difficult. (Philip Jarrett)

Other countries had independent air arms whose interest in attacking ships was often connected with a claim that airpower made navies obsolete. The first was the Royal Air Force (RAF), founded in 1918. The associated aircraft development and production organisation was the Air Ministry, which continued in that role for both naval and land-based aircraft after the Royal Navy regained control of the Fleet Air Arm in April 1939. Thus the two services shared R&D resources such as the Royal Aeronautical Establishment (RAE). Even when the RAF controlled the Fleet Air Arm, the Admiralty paid for the aircraft and supplied many of the observers, but there was no career path comparable to that in the US Navy, from pilot to admiral. That limited the air-mindedness of the naval officer corps. Also, without its own air staff to advise it, the Admiralty could not be sure that those providing technical advice truly understood naval issues. A subtler effect of the shift to the RAF was the limited aircraft capacity of British carriers, which made it difficult to combine adequate fighter defence with powerful strike capacity.⁷ During the Second World War the RAF continued to be responsible for land-based maritime strike aircraft, although their Coastal Command came under Admiralty operational control.

The US Army Air Corps (and later the Army Air Force) considered coast defence an important role, and therefore equipped its land-based medium bombers to drop torpedoes (it had no interest, however, in dive bombing). In the South Pacific, the Army Air Corps attacked Japanese shipping, on at least one occasion (the battle of the Bismarck Sea, 2–4 March 1943) achieving considerable success with skip-bombing.

Italy had a unified air force (like the RAF), although the Royal Italian Navy retained ship-based floatplanes and seaplanes. Air unification probably prevented the navy from building the carriers it wanted during the inter-war period (it finally received permission during the Second World War, after the Royal Navy demonstrated the value of carriers).

Air Attack

Before the advent of guided weapons, an aircraft delivering an attack was, in effect, the gun launching a projectile. The pilot gave the projectile both direction and forward velocity. Accuracy depended both on how well he aimed and on how well the projectile (bomb, torpedo, later rocket) followed through. The pilot’s need to steady up on course in order to aim was the main opportunity afforded the anti-aircraft defence, since until then the pilot was more or less free to manoeuvre. Conversely, anti-aircraft fire could ruin a pilot’s aim by forcing him to manoeuvre instead of steadying on course. The only exception to the straight run was that, like its sea-launched counterpart, an aerial torpedo could, at least in theory, be set to turn (angle) after launch. This possibility seems to have been realised only by the British, the Germans, and probably the Italians.

Prior to the Second World War it was accepted that a fleet in harbour might well be subject to night attack – as at Taranto in November 1940 – but it seems to have been assumed that ships at sea would be too difficult to locate. That was not at all true on a moonlit night, as wakes could be very visible. They were often phosphorescent, too. Night attacks on moving ships at sea, which were first mounted by the Italians in the Mediterranean in 1940, changed the situation considerably. Airborne radar much simplified night attack, although blind attacks were not possible until the advent of centimetric radar, which was limited to the Allies. Night also limited fighter defence. Even in 1945 the US Navy operated special ‘night carriers’, the other carriers being limited to day aircraft. Ships’ guns were the main night fleet air defence, and they were limited by the development of radar-controlled blind fire. As late as 1945 US doctrine for night convoy air defence was to make smoke and not to fire unless attacked, because muzzle flashes would become aiming points for the enemy.

For the inter-war US Navy, the single most important aviation development was the discovery of just how many aircraft the two huge carriers Lexington and Saratoga could operate. Exercises at the Naval War College showed that numbers of aircraft were paramount, and when he became Commander of Air Squadrons of the Battle Fleet (which then had the single small experimental carrier Langley) Captain Joseph M Reeves, Jr. asked his pilots how they could operate more aircraft. They discovered that instead of striking aircraft below as they landed – as in the Royal Navy – they could have them moved forward, protected from landing aircraft by a wire barrier. That made for a much shorter interval between landings. The shorter interval supported a much larger carrier air group. This was an inherently dangerous procedure, but it worked, and it gave the US Navy considerable numerical advantages over the Royal Navy and the Imperial Japanese Navy (which followed British operating practice). Unlike the British and the Japanese, the US Navy equated aircraft capacity to the size of the flight deck, which determined how many aircraft could be parked forward during landing, or how many could be spotted aft before take-off (leaving enough of a deck run to take off). Huge US carrier air groups made the balance of air forces at Midway much closer than the ratio of carrier numbers (four to three) might otherwise suggest. Its numerical advantage in turn made the US Navy more conscious of the value of carrier fighters, because it could have both a large fighter complement and a large striking force, even of massive torpedo bombers. Once it also had radar, the fighters made an enormous difference in fleet air defence. The US operating practice did have its drawbacks, however. With the deck loaded aft for a strike, it might be difficult to recover scouts. With aircraft filling the foredeck, it might be difficult to launch them. Arresting wires were rigged at the bow as well as the stern. The carrier would steam astern to recover aircraft: Essex class carriers were designed to steam astern at 20kts on a sustained basis. To launch aircraft when the deck was full, they were given hangar-deck catapults. Neither solution was particularly happy, and the US Navy was fortunate that it learned how to operate multi-carrier Task Groups, whose extra decks were a better solution. Conversely, the Royal Navy accepted many compromises, even in aircraft performance, because it assumed that its ships could accommodate so few aircraft. When it wanted more aircraft per carrier, it adopted double hangars, with their limited head-room (which made post-war modernisation of some wartime-built ships impossible). Saratoga is shown recovering her T4M torpedo bombers in the early 1930s. Unlike later US carriers up to 1945, she had a British-style closed hangar. That in turn made gasoline vapour explosions more devastating – and one such explosion doomed her sister-ship Lexington (the Japanese closed-hangar Taiho suffered a similar fate). Later US carriers had open hangar decks, which made it possible to warm up engines on them; that in turn made for faster launching of aircraft which had to be held below because they did not fit the parking area on the flight deck (whose size was set by the required take-off run).

The one ship-killing air weapon used during the First World War was the air-dropped torpedo, first employed by the Royal Navy and intended for mass use against the German High Seas Fleet had the war continued. This US Navy torpedo bomber has just dropped its weapon off Pensacola, 28 April 1920 – and it has porpoised. In 1922 the shore-based Torpedo and Bombing Squadron of the Atlantic Fleet successfully attacked the battleship Arkansas when she was steaming at full speed 70 miles from Norfolk. They made at least seven hits on her, and a miss hit the battleship North Dakota. This exercise demonstrated that air-launched torpedoes could be made to run straight, apparently an issue at the time.

It took time for navies to develop effective air-launched torpedoes and the tactics which went with them. Even then, the torpedo was by far the heaviest bomb load navies contemplated, and until the advent of engines in the 1000 and 1500hp class in the 1930s, torpedo bombers were invariably heavy and slow. The first production US Navy torpedo bomber, the T4M-1 of 1928, had a maximum speed of 114mph and required 14.1 minutes to climb to 5000ft. The Depression precluded replacement of the T4M, or even an upgrade with the new R-1820 engine, as proposed in 1931. The T4M could carry a torpedo or 1500lbs of bombs, and that became the standard for the next torpedo bomber, the Douglas Devastator. Given the combination of heavy bombing and torpedo attack in one aircraft, the inter-war US Navy assumed that carrier air strikes would mix the two types of attack, which would be combined with dive bombing by other aircraft. These T4Ms are shown on board the carrier Saratoga.

Reconnaissance was always the first step in an air attack: the sea is broad, and even a large convoy or fleet is only a small speck on it. Attackers with heavy loads had insufficient endurance for any kind of search. Instead, reconnaissance aircraft or ‘snoopers’, often cued by other intelligence, found the target and homed the attackers.⁸ Destroying a snooper might prevent an attack altogether. Since ships could generally be seen and shadowed from well beyond anti-aircraft gun range, it took fighters to deal with snoopers.⁹

Torpedo bombing

During the First World War, torpedo attack was the only form of air attack which actually sank moving ships at sea. It was practiced by both the British and the Germans, and in 1918 the British planned a mass torpedo attack against the German High Seas Fleet in harbour, to be mounted from aircraft carriers. The war ended before the plan could be executed.

To be effective a torpedo had to be relatively massive. Until the Second World War, engines suitable for carrier aircraft were not powerful enough to give a large enough aircraft an impressive performance. In the early 1930s the US Navy nearly abandoned the torpedo as an air weapon, reversing its position only with the advent of the Douglas TBD-1 Devastator – whose performance might have seemed sparkling in 1936, but was decidedly unimpressive a few years later. High bomber performance introduced a new problem. A torpedo dropped at high speed from a relatively high altitude typically oscillated as it fell towards the water. If it hit the water at the wrong angle, it would dive and it might also roll. A roll would cause its elevators, which were set to make it rise out of its initial dive, to act as rudders and cause it to hook. Something had to be done to stabilise the torpedo in flight so that it hit the water at the desired angle. The solutions were air tails which guided a torpedo into the water at the right angle, often coupled with breakaway protection for the nose of the torpedo.¹⁰ Relatively few wartime photographs show air tails of any type; presumably each user considered the concept secret.

The Regia Aeronautica, the Italian Royal Air Force, developed torpedo tactics before the war, but in line with its view that air power was general-purpose it did not form specialised torpedo bomber squadrons. The primary torpedo bomber was the Savoia-Marchetti SM 79 Sparviero, which could carry two torpedoes, as shown, although in practice they typically carried one. After SM 79s made successful torpedo attacks in 1940, special torpedo attack squadrons, the Aerosiluranti (Siluranti were torpedoes), were formed. They received enormous wartime publicity. (Philip Jarrett)

Throughout the mid-1930s carrier aircraft capable of lifting and carrying torpedoes had to be so large that they could not match dive bomber performance. For a time the US Navy planned to drop them altogether in favour of total reliance on dive bombers (the carrier Ranger was built without torpedo stowage). The fleet recommended not only elimination of torpedoes but restriction to two 500lb bombs for horizontal bombers; in 1932–4 BuAer retained both because it considered the performance penalties involved in carrying a torpedo or a third bomb were negligible. When it sketched a design prior to opening a new bomber competition in 1934, BuAer found that biplane configuration would limit it to 170mph, whereas a monoplane could reach 186mph; it included speed in the specification it released in 1934. This competition in effect saved the aerial torpedo in the US Navy, because it produced a torpedo bomber with high enough performance to have a reasonable chance of surviving enemy fighters: the Douglas Devastator. The rules of the 1934 competition embodied the speed BuAer estimated such an aircraft could reach; the Devastator actually made 206mph, and it proved remarkably free of mechanical defects. As a result, 114 were immediately ordered. Had the Devastator not been developed, further US carriers would probably have been built without torpedo stowage, their attackers limited to dive bombing. It would have been effective against carriers and cruisers, but not, the US Navy thought, against battleships – it took torpedoes to sink the huge Japanese Yamato and Musashi, for example. In addition to its modern design, the Devastator had the US Navy’s first hydraulically-folded wings. Unfortunately aircraft, particularly engine, technology was moving so fast that within a few years it was obsolete. The TBD was powered by a 900hp R-1830 (an abortive version offered in 1940 to the Dutch used a 1200hp R-1820; note the difference in output in an engine of about the same size). According to a post-war BuAer history of attack aircraft development, further development of the TBD suffered because the navy came to emphasise dive bombing instead. Once the fighters and dive bombers exceeded the performance of the Devastator (in 1938), BuAer ran a competition for a faster new torpedo bomber, which became the Grumman Avenger. This time it wanted 50 per cent higher speed and a bomb bay sufficient for a torpedo, three 500lb bombs, or fuel for a range of 3000 miles (during design the bomb bay was enlarged to accommodate an additional 500lb bomb). Like other US (and Japanese) torpedo bombers, the TBD could also be used as a level bomber, typically carrying a single 1000lb or three 500lb bombs. For that purpose it, and the Avenger which succeeded it, had a Norden bombsight. In its case the bombardier’s window was under the belly, normally covered by doors for streamlining (it could not be used if the torpedo was carried). After making a good showing (as a level bomber) in carrier raids on the Mandated Islands in February 1942, and (as a torpedo bomber) at the Coral Sea in May, Devastators were nearly wiped out at Midway. One reason why was that they carried their torpedoes tipped down at a 9° angle. This flight deck photograph suggests the reason why: the torpedoes were carried parallel to the deck, presumably for loading, but the aircraft was tipped back. The Mk 13 torpedo had to be dropped parallel to the water, which required the Devastator to adopt a nose-up attitude which in turn made for slow speed. Typically torpedoes were dropped at an altitude of no more than 100ft and at an air speed of no more than 120mph. These aircraft of VT-6 are shown on board Enterprise shortly before being launched at Midway. Only four of the fourteen launched managed to return to the ship, one being so badly damaged that it had to be thrown overboard. Of a total of forty-three Devastators launched that day, only six made it back to the carriers, two being forced to ditch. The entire squadron launched by Hornet, VT-8, was wiped out. At this time US tactics called for coordinated attacks by dive and torpedo bombers, the idea being that an enemy would be unable to deal with both at the same time. Escorting fighters were to cover the entire attack group. In fact the carrier air groups involved spread out in flight and arrived at the Japanese carriers piecemeal. It happened that the torpedo bombers arrived first, and that they drew the Japanese fighters down to their level to attack them. That left the field open to the dive bombers which soon followed. Had the three types of aircraft arrived together, the Devastator might have emerged from the battle with a far better reputation as the stablemate (with much the same engine) of the Dauntless.

As the British sought to drop torpedoes at higher speeds and from greater altitudes in the 1930s they experimented with means of stabilising them in flight.¹¹ Ultimately they adopted the ‘air rudder’ or air tail they first saw on Norwegian torpedoes. Even then the strength of the torpedo limited drop speed. For example, a bomber approaching at higher than drop altitude had to fly level above the water for a time as it decelerated. By 1942 dive brakes were important because they minimised the level decelerating run above the water. It helped that current British naval torpedo bombers had dive brakes because they had an alternative dive-bombing role (so did the Brigand land-based torpedo bomber then under development). By late 1942 the British wanted their future air-launched torpedo to stand a 300ft drop at 250kts, which was far beyond existing capability.¹²

The Japanese used a wooden tail frame and special flippers for control in the water. The Germans used a wooden box air tail (three horizontal and two vertical surfaces) and an anti-roll ring using a pair of gyro-controlled fins. The Italian air tail had a longer span and incorporated an anti-roll mechanism using gyro-controlled horizontal rudders (the British monoplane air tail was also gyro-controlled).¹³

The US Navy seems to have come late to understanding that it needed special fittings. By 1944 its Mk 13 torpedo had a tail ring (shroud ring), a box air tail, and a wooden shroud (the ‘pickle barrel’) around its nose. Given these fittings, torpedoes could be dropped at speeds as great as 400kts and at altitudes above 2000ft.¹⁴

Torpedo attack was inherently dangerous because the pilot had to point his aircraft more or less directly at the target, using a torpedo director like that on board a ship to solve the triangle of ship course and speed and torpedo course and speed. In 1934 the Germans demanded that future aerial torpedoes be capable of angling; they may have been the first to do so.¹⁵ In 1937 an RAF officer had the same idea, and during the war British aerial torpedoes could angle, the attacker using a Type F sight.¹⁶ The Italians seem to have had the same idea. During the war the British initially rejected the US Mk 13 torpedo partly because it lacked this feature.¹⁷

The Avenger, the standard US torpedo bomber of the Second World War, arose from a 1939 design competition. Like the Helldiver designed the previous year, the Avenger was designed around the next-generation engine (the 1700hp R-2600). Its most important new feature was that the torpedo was carried internally. Like other torpedo bombers, the Avenger was also seen as a level bomber. The big internal bay could accommodate four 500lb, two 1000lb or one 2000lb bomb. In July 1942 VT-6 experimented with glide bombing. Aircraft dove at a 45 to 60° angle from 6500ft, releasing their bombs at 2500ft. They found that they could place their bombs within 40ft of a moving target. The squadron commander recommended removing all horizontal bombing gear, but BuOrd kept the Norden bombsight because it felt that under some circumstances the earlier technique might still be useful (it turned out that pilots used only the stabilised bombing approach part of the Norden, as an autopilot for use during long flights; in 1944 it was replaced in new production aircraft with an autopilot). Glide bombing did not require the displacement gear (crutch) used by dive bombers to keep their bombs away from their propellers as they dove; at a 60° angle the Avenger would not be struck by its own bomb. However, it had never been stressed for glide/dive bombing, and occasionally Avengers disintegrated during bombing dives. The aircraft could not afford the required 400–600lbs of strengthening, so Grumman added strength at what it estimated were critical points. Accelerometers were installed to indicate to pilots that they were approaching dangerous conditions. The problem was not really solved until March 1945, when Eastern Aircraft (which was producing Avengers under license), redesigned the Avenger using higher-strength alloy and at the same time redesigned the wing hinges. This TBM-4 was scheduled to enter production in August 1945, when the war ended the Avenger programme. These Avengers are shown on 15 March 1950.

There was little chance that a single torpedo bomber could hit a manoeuvring ship. Those on the target ship would see the bombers drop their weapons, and the ship was nearly as fast as the torpedoes. Evasion often succeeded. During the inter-war period, tacticians developed an answer. Aircraft would attack in groups (equivalent to firing a spread of torpedoes from one direction). At least two groups would attack together, from both bows.¹⁸ At least in theory this ‘hammerhead’ or ‘hammer and anvil’ approach would ensure that however the target ship manoeuvred, some torpedoes would hit. The faster the target, the more important to ensure that she had little or no manoeuvring time after torpedoes were in the water. That favoured minimum-range attacks at low level. Much depended on the element of surprise. The faster the attacker, the less chance the target had to evade.¹⁹ It also helped to put the torpedo into the water as close as possible to the target – but that made the attack more dangerous.

A November 1942 British description of German convoy attack tactics was that aircraft typically approached at about 150ft from astern or on the quarter of a convoy, although occasionally they circled outside gun range to gain better positions. Sometimes they turned towards the convoy individually and then turned away, to draw gunfire. Final approach and release were generally from bows or quarter at 50–80ft, with an outside limit of 180ft. Average dropping range was 1500 yds, with outside limits of 500 and 4000 yds. Attacks on convoys were generally by five or six aircraft, with a maximum of ten. Unescorted ships were generally attacked singly, though at times two or three made concerted attacks. After attacking, aircraft turned away and made off at low altitude. Typically torpedo attacks were made in conjunction with dive- and high-level bombing attacks. At times the Germans (e.g. against Russian convoys) dropped from unusually great heights. In one such attack, against Convoy PQ17 in 1942, torpedoes were seen to bounce more than their own height out of the water.

A Mk 13 torpedo about to be loaded on board a TBM-3 Avenger displays two of the three modifications which made the torpedo effective at high drop speeds and altitudes: the wooden ‘pickle barrel’ around the nose and the box tail. The third new feature, the tail ring, is hidden by the box tail. Unlike the British and the Italians, the US Navy did not adopt long-span air tails because it carried its torpedoes internally (even the Devastator carried its weapon semi-internally). This torpedo was being loaded on board the light carrier San Jacinto during the battle of Leyte Gulf, October 1944. US torpedo tactics changed radically during the war. In 1941 standard practice was to approach a low altitude. During the autumn of 1941 VT-3 developed a new tactic, in which the aircraft approached the target at high altitude, then dove to attack altitude near the target. That improved the pilots’ view of the target, and the high-speed dive to drop altitude improved protection against enemy anti-aircraft fire.

The B5N (‘Kate’) was the standard Japanese carrier torpedo bomber in 1941, the aircraft which attacked Pearl Harbor and which fought at the Coral Sea and at Midway. At the time it was the highest-performing carrier torpedo bomber in the world (though one might say that the others, the Swordfish and Albacore and the US Devastator, were not very impressive). Design work (7-Shi specification, i.e., FY 33) began in 1932, about two years earlier than that on the Devastator. After none of the designs offered proved satisfactory, the navy issued another specification (10-Shi: 1935) calling for a maximum speed of 180kts and a range of 540nm carrying the usual 800kg torpedo. It first flew in January 1937. The version in service at the outbreak of war in 1941 was B5N2, which offered higher performance to deal with modern fighters: maximum speed was 204kts, and normal range was 528nm. (Philip Jarrett)

The B6N Tenzan (‘Jill’) was the planned replacement for the ‘Kate’ which carried out Japanese carrier torpedo attacks at the outset of the Pacific War. It was designed to a 1939 (14-Shi: FY40) specification calling for a maximum speed of 250kts (200kts cruising speed) and a range of 1000nm with the standard 800kg load (torpedo or bombs). The speed was comparable with that of the US Avenger designed at about the same time, and the range was chosen to support the preferred tactic of attacking beyond the enemy’s attack range. The Tenzan was designed at a time of steeply rising engine performance, its engine being about 80 per cent more powerful than that of its predecessor. Although the prototypes were complete in the spring of 1941, the Tenzan had serious teething troubles, and it did not enter production until 1943. It fared poorly against US naval fighters in its first major engagement, the battle of the Philippine Sea in June 1944. (Philip Jarrett)

In the Mediterranean the British found that barrage fire could force Italian torpedo bombers to release their weapons at greater ranges, so that after 1940 they were relatively ineffective against fleet units (but not convoys).²⁰ In addition to conventional torpedoes, the Italians had air-launched circling torpedoes specifically for use against convoys, roughly as the Germans used pattern-running torpedoes launched by submarines. Circular runs were more efficient than the German zigzag inside a convoy, and the aircraft did not have to fear a torpedo coming back at it.²¹ The Germans later adopted the larger of the two Italian circlers.

Because a torpedo bomber approached almost horizontally, it was susceptible to the same sort of smokescreen which would frustrate an attacking ship. Most wartime radars were not good enough to permit blind attacks. Several navies found smokescreens effective against torpedo bombing.²²

Torpedo bombing was the dominant form of wartime night anti-ship attack because of its relative simplicity and because a ship presented so large a target. In 1943–4 the Imperial Japanese Navy used land-based long-range G4M (‘Betty’) torpedo bombers at night (the US Navy did not yet have many carrier-based night fighters). For example, one torpedoed the US carrier Intrepid in her rudder in November 1943. Initial attacks were conducted by single aircraft. The target ship might be unaware of the attack until the torpedo struck, hence would not take evasive action. In order to line up its target visually, the bomber generally laid a path of floating flares the movement of which indicated windage. It then turned back and flew down the path to drop its torpedo. This type of attack made the development of blind-firing anti-aircraft weapons more urgent.

Aichi’s B7A Ryusei torpedo bomber (‘Grace’) was part of the 16-Shi (1942) programme. It was intended to extend the reach of Japanese carriers and thus to minimise the problem of carrier air defence: if the Japanese fleet could outreach the US fleet, and if its aircraft could penetrate US defences, then it could strike without being struck. The Japanese consistently managed to outrange the US fleet, but the combination of effective fighter control and effective anti-aircraft fire made that outreach useless. The Ryusei was intended to replace both the standard attack aircraft: the B6N torpedo bomber and the D4Y dive bomber. Given enough engine power, an airframe stressed to dive-bomb could lift a torpedo. That was the case with both the US SB2C Helldiver (although it was not used as a torpedo bomber) and the British Barracuda (a torpedo bomber used exclusively as a dive bomber). Manoeuvrability was to be equal to that of a Zero (A6M) fighter, to give the Ryusei reasonable immunity from interception. Normal range was to be 1000nm (maximum 1800nm). The prototype was completed in May 1942. Note that the operational concept considerably predated Midway. Production seems to have been hampered by slow engine development, as it did not begin until April 1944. (Philip Jarrett)

As the US fleet came closer to Japanese land bases, night torpedo attacks became more common, using shore-based single-engined aircraft. Typically a reconnaissance aircraft spotted the fleet at dusk and provided a rough location to the strike force. Night tactics employed off Palau in the spring of 1944 were considered typical. Enemy aircraft milled around outside gun range, then formed up for a sudden run in at low altitude (200–300ft) and medium speed (150–180kts), low altitude having been chosen to avoid US radar. They approached in a rough line abreast. During each such attack a single aircraft stood off about 20–30nm away, probably co-ordinating the attack.

Maximum strike range from base was about 150nm.²³ This distance was probably related to the uncertainty of future target position due to the time interval between report and attack. The strike force spread out into a wide arc once it got to within 15–20nm of the fleet. ‘Betty’ and ‘Jill’ both carried what the British called Air to Surface Vessel (ASV) radar, which was equivalent to the early-war British metric-wavelength set using dipole antennas along the body of the aircraft. It could not look dead ahead. At any height above 1000ft it could detect a battleship at a range of 45nm. It appeared that the strike force spread out either because homing on search radars became confused (the fleet had so many of them) or because ASV was inaccurate looking right ahead. The attack then spread out, aircraft dropping to 500ft and forming smaller attack groups.

The standard British Monoplane Air Tail, under a Beaufort. (Dr Raymond Cheung)

An Italian torpedo with air tail, under an SM 79.

Japanese doctrine was to place the target between the striking force and the moon (the preferred time was when the moon was between 10° and 50° above the horizon). The target was illuminated either by the shadowing aircraft calling in the strike or by two specially-assigned strike aircraft. In either case the shadowing aircraft dropped course lights behind the target when the strike force was about 20nm away. As soon as they could be seen by the strike force, it altered course to line up with these flares. When in the desired position, the strike force gave the signal to illuminate, at which time flares were dropped on the side of the target away from the strike force.

Strike forces could vary from three to as many as forty aircraft; by late 1944 carrier strikes on Japanese airfields were limiting typical numbers to no more than twenty night torpedo bombers. Aircraft flew most of the way to the target at 3000–4000ft, and sometimes not more than 1000ft, which would limit long-range radar detection. New Japanese tactics (as of late 1944) included a higher approach so that the attackers could use their own radar effectively. Striking forces sometimes homed on US air-search radars.

The Italians developed Motobomba, a circling electric torpedo which could be dropped in the path of a moving force. In that way it functioned as a cross between a torpedo and a mine, since it covered a larger area than a mine but did not have to be aimed like a torpedo. Motobomba was adopted by the Germans in the Mediterranean. (Dr Raymond Cheung)

By 1944 the Japanese were well aware of ‘Window’ (chaff: strips of aluminium foil or other radar reflectors), which had been used against their German allies the previous year. During the invasion of Saipan (June 1944), Japanese attackers made frequent and varying use of it, in US eyes demonstrating a good understanding of its potential. Often a group of aircraft dropped ‘Window’ while orbiting, then left the infected area to attack from a different direction. It was intended to leave US radar operators uncertain of whether there were still enemy aircraft in the infected area, hence unwilling to concentrate defending fighters on the new attack. At other times raiders attacked from the infected area. It was difficult to detect Japanese aircraft until they were about 5nm closer than the near edge of the ‘Window’ zone. The Japanese also began to exploit US IFF (Identify Friend or Foe). In this way a group of Japanese aircraft were able to approach 7th Fleet units on 6 November 1944 near Leyte and inflict damage.

Level Bombing

The initial alternative to torpedo attack was level bombing.²⁴ It was the only way to deliver a bomb capable of penetrating capital-ship decks, a possibility dramatised in bombing trials conducted by the US Army Air Service in 1921. It was obvious at the time that the attacks had not been particularly realistic, since the targets had been anchored, neither shooting back nor capable of damage control. Even so, level bombing was heavily promoted between the wars by air forces as a rationale for their widespread claim that navies were obsolete.

It was widely recognised during the inter-war period that a single bomber would have a very limited chance of hitting a moving, particularly a manoeuvring, ship. A group of bombers dropping a pattern of bombs could do better. As with the torpedo bomber, level bombing required the attackers to fly a predictable course as they approached the target. The path of the bomb depended on the bomber’s course and speed and on the wind: in effect, the bomber is the gun firing the bomb, and its course and speed are equivalent to a gun barrel and to muzzle velocity. Aficionados of Second World War bomber movies will recognise this requirement, which made attacking bombers vulnerable to anti-aircraft gunfire. Conversely, it was widely understood that anything which forced level bombers to manoeuvre as they approached their targets – to jink – would ruin their aim.

Initially the RAF both in the Mediterranean and in Coastal Command in the North Sea relied heavily on light bombers like this Blenheim. It soon learned that the only effective bombing technique was very low level attack. As very few bombers were available at the time, the defence tended not to be saturated, so losses were severe. Note also the complete lack of forward-firing armament, which might have been used to suppress anti-aircraft fire. At one point Coastal Command felt compelled to revert to pre-war tactics in which aircraft attacked at much higher altitude – and tended never to hit, but at a low cost in casualties. Blenheim units rotated through Malta early in the Mediterranean war, but they were relatively ineffective. Most Axis merchant ships sunk in the Mediterranean fell victim either to submarines or to surface ships; others were destroyed in or near port by bombing or mining. Overall, mining was far more effective than direct air attack on ships at sea. (Philip Jarrett)

How long the bomber had to fly straight and level depended on how good its bombsight was; the better the sight, the less time it required for the run-in. Until the run-in, the bomber could manoeuvre fairly freely. The US Navy considered level bombing so important that its Bureau of Ordnance sponsored development of a new kind of bombsight, conceived and developed by Carl F. Norden. It was gyro-stabilised, and that in turn made it possible for the bombardier to measure, in effect, the bomber’s ground speed by tracking the target visually. Norden once remarked that the best anti-aircraft fire-control technique would be equivalent to his bombsight, operating in reverse. Just before the Second World War, the US Navy estimated that a bomber required a 45-second run-in – defenders had no more than 45 seconds to get a fire-control solution and fire their bursts. It might take as much as 20 seconds to load and fire a gun and for its projectile to reach about 15,000ft or more. On the eve of their entry into the Second World War, US Navy anti-aircraft gunners considered level bombing the most difficult threat to counter. They may have been overly impressed by the short run-in a Norden required. The US Army bought the Norden bombsight in preference to a device it had developed, and a legend grew up about its performance and the need to maintain its absolute secrecy.²⁵

Gyro-stabilisation made the Norden equivalent to an auto-pilot, since it controlled the bomber during its final approach to the target. Wartime US Navy Avenger torpedo bombers (TBFs and TBMs) all had Norden bombsights, which were often employed as autopilots.

Level bombing from high altitude (i.e., beyond easy anti-aircraft range) proved almost entirely ineffective during the Second World War, mainly because so much uncertainty, for example concerning wind between bomber and surface, and also because of inaccuracy in tracking targets on the surface. For example, in 1940 the Royal Navy’s Force H was repeatedly attacked by formations of Italian level bombers. It found that its anti-aircraft fire did not break them up, but it did keep them too high to accomplish much. The failure of level bombing was a great wartime surprise. The only important exception seems to have been bombing by Fw 200 Condors attacking convoys, whose merchant ships were not free to manoeuvre; the Condors apparently had excellent bomb-sights.²⁶

Skip-bombing was an alternative. It seems to have been invented before the war by the RAF, and used from about 1940 onwards. The bomber approached at low level, and it might duck and weave as it did so. The approach ended at low altitude and at extremely short range, the bomb being dropped into the water. It was intended to skip like a rock skipped across water, to hit the side of the target ship. Once the bomb was gone, the bomber pulled up, often flying over the target ship at masthead height.

From the target’s point of view, skip bombing was not too different from torpedo attack, but the attacker was flying at much higher speed and also at somewhat greater altitude. Skip bombing was brought to the US Army Air Force in 1941 by General H H ‘Hap’ Arnold, who learned about it from the British. It may have been invented independently by General George Kenney for his Fifth Air Force in the south-west Pacific in 1943, and it was used successfully against Japanese warships and merchant ships in the 1943 battle of the Bismarck Sea.²⁷

The British ‘bouncing’ bomb was a kind of skip bomb, a rotating object intended to hit the water and skip off to hit a distant vertical object. Because it was spinning, when it hit the vertical wall, it would descend before exploding. It was developed specifically to attack German dams. By the end of the war the British had Highball, a miniature version. At the end of the war they were working up a squadron of RAF Mosquitoes to attack the Japanese fleet in Singapore from a carrier. Highball would have bounced over torpedo nets, but it would have inflicted torpedo-like underwater damage. The war ended before the attack could be mounted.

The British seem to have been unique in developing a further kind of bombing attack, featuring the ‘B’ (buoyant) bomb. This weapon would be dropped alongside a ship. Rising in the water, it would explode below the surface, creating a shockwave which in theory might break a ship’s back. ‘B’ bombs were never used in combat, and they were all ordered destroyed in 1946. The ‘B’ bomb exemplifies anti-ship weapons which, although devastating to their targets, proved entirely impractical to deliver.²⁸

A US B-25 Mitchell climbs out after delivering a skip-bombing attack on a Japanese freighter off New Britain, 2 November 1943. (US Office of War Information wartime release)

Air-launched rockets were the ultimate strafing weapons. This is the largest one operational during the Second World War, the 11.75in US Tiny Tim (British Uncle Tom), whose warhead was a 500lb bomb. It was powered by four standard 5in rocket motors. Initial tests failed when the blast of the motor damaged the launch aircraft. Tiny Tim was used experimentally against Japanese shipping in March 1945. Franklin and Intrepid both strongly recommended production, and Intrepid aircraft successfully fired Tiny Tims during the invasion of Okinawa in April 1945. However, the Kamikaze hit on Franklin set off Tiny Tims on her hangar deck, on board bombed-up aircraft, and they added considerably to her damage.

Dive Bombing

The most important new development in anti-ship air strike warfare between the wars was dive bombing. A form of dive bombing was developed during the First World War by several countries, notably the British. Fighters or light bombers dove at a steep angle, in effect aiming their light bombs (20 or 30lbs each). The British Fleet Air Arm continued to develop such tactics, which it called convergence attacks, after the war. The US Marine Corps became interested in this form of precision attack, presumably due to its experience in counterinsurgency in Central America and the Caribbean. Given its close connection with the Marines, the US Navy also became interested. The key US development was to heavy bombs capable of disabling aircraft carriers and sinking small warships. Not only could a dive bomber hit a manoeuvring target, it was a much more difficult target than a torpedo or level bomber flying a straight course. Attacks developed suddenly, and it appeared that fire-control systems designed to deal with level bombing could not cope. US Navy dive bombing was popularised in the 1931 movie ‘Hell Divers’, starring Wallace Beery and Clark Gable. The movie was named after the F8C-4 Helldiver dive bomber. The movie seems to have made a considerably greater impression on other navies than reports of US exercises.

The Douglas SBD Dauntless succeeded magnificently at Midway, sinking four Japanese aircraft carriers. It fought in all five carrier-vs-carrier battles in the Pacific, and many considered it superior to its successor, the Helldiver. It operated both as a scout (S) and as dive bomber (B). In the armed scout role it carried a 500lb bomb and extra fuel; in the dive-bomber role it carried a 1000lb bomb, as shown here. The Dauntless could also operate as an unarmed scout, with a range of 1445 miles, compared to 1300 miles with the 1000lb bomb. Although production ended in 1944, the Marines were still flying Dauntlesses in the Philippines when the war ended. Although it was small, the Dauntless did not fold its wings and thus occupied more deck or hangar space than its successor. BuAer never seriously considered adding the weight of a folding mechanism, because that would have cost too much fuel or bomb load. One weight it did add was an ASB (air to ship radar), which in turn required a new electrical system (this was in the SBD-4, which entered production in the autumn of 1942).

A 500lb bomb being loaded onto a US Navy dive bomber, January 1942. The cradle around the bomb is the crutch (trapeze) which swung it out so that it did not foul the propeller as it fell roughly parallel to the diving path of the aircraft.

A dive bomber had to carry added weight to deal with the stress of pulling out of its attack dive. That is why US and Japanese dive bombers in service in 1941–3 could not carry torpedoes (conversely, torpedo bombers could not handle the stresses of dive bombing). During the war a new generation of much more powerful engines made it possible to eliminate this distinction. The most prominent example was the British Barracuda, conceived as a dual-purpose dive and torpedo bomber, but used in practice as a dive bomber. The Japanese B7A Ryusei (‘Grace’) was analogous. The US Helldiver (SB2C) could carry a torpedo, but it was never used in combat for that purpose. Somewhat similarly, the Avenger was often used as a glide bomber, although it was not stressed for such tactics, and from time to time it disintegrated while bombing.

Generally, glide bombing (attack at a shallower angle) was practiced as a less straining alternative to dive bombing, since it still gave a better aim than level bombing. During the early part of the Second World War, the distinction between the two was not always drawn. In Norway, for example, until the Germans had airfields ashore they used long-range bombers (Ju 88s) to attack the British fleet offshore. Those aircraft often made shallow (glide-bombing) dives. British long-range barrage tactics often frustrated them. By way of contrast, the short-range Stuka (Ju 87) made true dive-bombing (near-vertical) approaches.

Aircraft structural strength limited the weight of the dive bomb, the heaviest probably being the German 1600lb armour-piercing bomb. When the Royal Navy’s Fleet Air Arm attacked the battleship Tirpitz in 1944, pilots kept their bombs on board as long as they could to ensure hits. They did not give the bombs enough altitude to accelerate enough to penetrate the ship’s protective decks. In 1941 the US Navy became interested in a solution in the form of a rocket boost, but it did not materialise. Thus dive bombing was unlikely to sink a battleship, although it might do significant damage. By manoeuvring, a diving pilot could keep his bomb pointed at a manoeuvring warship. His chance of hitting was far better than that of a level bomber. The closer the dive bomber came to a vertical dive, the closer the bomb would follow where the bomber’s nose pointed. The further from the vertical, the more important it was for the bombsight to compensate for bomb ballistics. Because it used near-vertical tactics, the US Navy relied on a simple tube gunsight. Because they attacked at a shallower angle, they required a more elaborate bombsight (development of which lagged badly in 1932–8).

The Curtiss Helldiver (SB2C) was bought ‘off the drawing board’ to replace the Dauntless in the autumn of 1940 due to the obvious threat of war. The Helldiver was designed for a 1938 competition in which the engine was the next-generation (after the Dauntless) R-2600 producing 1700hp, carrying the standard 1000lb bomb internally. The urgent order and equally urgent preparation for large-scale production made it difficult or impossible to cure defects in the design, ultimately limited strength (Helldivers sometimes disintegrated while diving, and sometimes even when sitting on a runway) and limited longitudinal stability (Helldiver dimensions were set by a requirement that two be able to ride a 41ft × 48ft carrier elevator). Modifications increased weight to the point where the Helldiver was little faster than a Dauntless, and pilots much preferred the earlier aircraft: the Helldiver was designed to operate at 11,900lbs, but at the end of 1944 it weighed 16,800lbs. Power did not increase proportionately; the later R-2600 produced 1900hp. From an attack point of view, the important advantage of the Helldiver was its large bomb bay, which made it possible to increase the bomb load as BuAer realised in 1942 that the 1000lb bomb was not enough. The bomb bay could accommodate either two 1000lb or one 1600lb AP bomb, and a special adaptor made by Curtiss made it possible to carry either a 2000lb bomb or a torpedo (which was partly external). Note that the 1600lb AP bomb did not figure in the 1944–5 attacks on the Japanese super-battleships.

Pre-Second World War exercises suggested that dive bombing would often take ships entirely by surprise. Patrolling fighters often found it difficult to follow the dive bomber into its low-altitude escape after releasing its bomb. A dive bomber was a very difficult anti-aircraft target, because its altitude was changing so rapidly. For example, a bomber diving at 300kts (which was not fast for 1941) would complete a dive from 12,000ft to bomb release in only 20 seconds. The US Navy seems to have been unique in adequately simulating dive bombers using radio-controlled targets (the British Queen Bee could not dive-bomb). Lack of realistic experience may have made the Royal Navy unduly optimistic about its ability to deal with this threat, although it was certainly aware of it. German use of dive bombers, particularly in the Mediterranean, seem to have been a terrifying surprise.

A single dive bomber was bad enough, but the tactic lent itself to multiple simultaneous attacks from different directions, because attacks were over so quickly that pilots did not have to make much allowance for the movement of their targets. Moreover, dive bombing was far more accurate than level bombing. In June 1937 the Germans tried both kinds of attack against the radio-controlled target ship Zahringen. Level bombers scored 2 per cent hits; dive bombers scored 40 per cent, and the Inspector for Naval Airmen spoke of the ‘amazing superiority of the Stuka over the ordinary bomber’.²⁹ In 1944 a German officer commented sourly that this was true only as long as there was not a lot of anti-aircraft fire concentrated around the target, because in that case an aircraft diving straight down made an excellent target.

This Barracuda was sent to the US Navy’s test field at Patuxent River for 1944 tests. Because the Barracuda did not function well in hot, humid weather, the British Pacific Fleet was equipped with Avengers instead, even though they did not offer dive-bombing capability. (David Hobbs)

As it began to rearm in 1933–4, the Royal Navy came to realise that it could not match the numbers of carrier aircraft in the Japanese navy, which it considered its most likely enemy. In November 1934 the Admiralty made the case for a carrier-based dive bomber specifically to gain air superiority by disabling or sinking Japanese carriers.³⁰ As a fallback, the dive bomber could be used as a fleet fighter, but dive-bombing performance was much more important than fighter performance. A formal specification (O.27/34) issued that December produced the Blackburn Skua. It made excellent sense as long as the main air threat to a fleet at sea came from enemy carriers. Given the rapid advance in aircraft performance at the time, the value of fleet fighters was declining. Screening ships could no longer provide enough warning to launch interceptors, and no carrier could support a sustained fighter patrol. The new high-performance fighters were minimum airframes wrapped around the most powerful lightweight engines, so they lacked the endurance to remain on patrol for long. That was a reason that fighter direction based on early detection was critical for the Battle of Britain a few years later.

Barracudas on Formidable being armed with 1600lb AP bombs during August 1944 strikes against the German battleship Tirpitz (Operation ‘Goodwood’: strikes on 17 July and 22, 24 and 29 August). The aircraft in the background are US-supplied Corsairs. In addition to her anti-aircraft battery, in resisting the Fleet Air Arm attacks Tirpitz fired both her 15in and her 5.9in LA guns in barrage mode, with time-fused HE ammunition (German accounts give the numbers of rounds fired). (David Hobbs)

Unfortunately for the Royal Navy, by about 1935–6 it seemed that a future war might well be fought in European waters, where an enemy could deploy large numbers of aircraft at shore bases. No naval dive-bomber force could neutralise those bases, although it turned out that intense air attacks could shut a few of them down for brief periods. Since the Royal Navy could not secure air superiority under these circumstances, it adopted armoured flight deck (actually armoured hangar) carriers whose limited aircraft capacity was devoted entirely to strike aircraft. A carrier facing air attack would strike all of her aircraft below, into the armoured hangar. Fleet anti-aircraft guns would be the sole defence. It seems to have been assumed that this was a reasonable choice, that British anti-aircraft gunnery would make attacks on the battle fleet difficult at best. In practice the Royal Navy was unwilling to depend entirely on its guns, so it continued to buy small numbers of fighters – adapted Gloster Gladiators and then the purpose-built Fairey Fulmar. It is not clear whether those responsible realised that the advent of radar would soon make shipboard fighters effective.³¹

By 1944 the Royal Navy had a fully effective dive bomber in the form of the Fairey Barracuda, and it was used in 1944 strikes against the German battleship Tirpitz. On 3 April (Operation ‘Tungsten’) forty Barracudas in two waves escorted by eighty-one fighters) achieved complete surprise. The ship had just been repaired after damage by midget submarines in 1943 (she was about to run speed trials, one anchor having been raised). Surprise was complete, partly because the radar recently installed in the area was not yet operational. The attackers divided into groups from the two quarters and from ahead, attacking nearly simultaneously. The ship’s smokescreen was very thin, her foretop completely exposed to provide an aiming point. The fighters strafed the ship to suppress anti-aircraft fire (many of the ship’s anti-aircraft guns were unshielded, the shields ordered much earlier not yet having been delivered), and the Barracudas attacked using 1600lb AP bombs, 500lb SAP and also medium-capacity (HE) bombs; there were also a few 600lb depth bombs. The first strike scored nine hits and a profitable near-miss (all with 500lb SAP); the second (also 500lb SAP), five hits and three near-misses, the reduction being due to a thick smoke cloud generated after the initial attack. Unfortunately the ship was not seriously damaged. Bombs were released from too low an altitude (the Germans claimed 300ft to 1500ft) to penetrate the ship’s armoured deck (initial British reports claimed that bombs were dropped from 2500ft and 3500ft).

DNC later pointed out that even when dropped from 3500ft, a 1600lb AP bomb would only just penetrate the ship’s armour deck over the machinery, where it was thinner than over the magazines; a bomb dropped from 2500ft should not have penetrated the armour deck. Only two of the bombs reached the armour deck; two others bounced off the 2in upper armour deck, and one lodged halfway through it. The greatest damage was done by a bomb (probably 1600lb AP) which struck the water near the ship, penetrated the side plating under the armour belt, and detonated near the main torpedo bulkhead. Unfortunately there was no significant damage to machinery or armament, and the ship was ready for sea again in about a month: hence a second series of raids mounted on 17 July and on 22, 24 and 29 August (Operation ‘Goodwood’). Against these raids the Germans used observer posts some distance from the ship to trigger adequately thick smokescreens and anti-aircraft fire. Even so, an eighty-plane raid mounted on 24 August managed to score two hits (out of 23 AP bombs dropped: 18 × 1600lb AP, 5 × 1000lb AP) with AP bombs plus two (and one possible and one probable) out of ten 500lb SAP bombs. One of the AP bombs hit the port side of the upper deck abreast the forward conning tower and penetrated through the armour deck to the lower platform (inner bottom).

The D3Y (‘Val’) was the stablemate of the B5N torpedo bomber, and as such fought at Pearl Harbor and in the earlier carrier-vs-carrier battles. It was unique among its generation of Japanese carrier aircraft in having a fixed undercarriage. It was built to a 1936 (11-Shi) specification, and performed carrier qualification trials in 1940. The normal load was a single 250kg (550lb) bomb on the usual dive-bomber crutch; two 60kg bombs could be carried on wing racks outboard of the dive brakes. The contrast between the 250kg warload and the typical 800kg warload of a torpedo/level bomber reflects the vast difference between an aircraft stressed to pull out of a more or less vertical dive and one which would deliver its weapon in level flight. Maximum speed was 232kts, and normal range was 730nm. (Philip Jarrett)

The D4Y Suisun (‘Judy’) was in effect the stablemate of the B6N, the standard Japanese dive bomber of the latter stages of the Pacific War. Like its predecessor the D3A ‘Val,’ it was designed to deliver a single 250kg bomb, a considerably lighter weapon than that wielded by US Navy dive bombers. However, like other Japanese carrier attack aircraft, it had a considerably longer range. It was conceived in the wake of unsuccessful tests of the German He 118 in Japan. The He 118 demonstrated high speed but it disintegrated in flight. The D4Y was designed to an experimental 13-Shi (1939) specification calling for a speed of 280kts (cruising speed 250kts) and a range of 800nm, the latter not matching that of the torpedo bomber, but still quite long. Range without a bomb load was to be 1200nm. On this basis the D4Y outperformed all other carrier dive bombers in service during the Pacific War. Unusually for Japanese carrier aircraft, the D4Y was powered by an in-line liquid-cooled engine, in this case a license-built version of the German DB 605. The only other carrier attack aircraft with this type of engine was the British Barracuda. The US Navy rejected such engines on the ground that they were too vulnerable to battle damage, even by a stray bullet; it preferred the much more rugged radials. Prototype performance was very impressive, but simulated dive bombing revealed unacceptable wing flutter, and production aircraft were used for carrier-based reconnaissance. The dive-bombing problem was finally solved and D4Y accepted as a dive bomber in March 1943. Thus it had missed the early carrier battles, but was available in numbers for the battle of the Philippine Sea – in which it was not nearly fast enough to evade US fighters. Among other sacrifices made for speed was any form of protection. The engine itself caused problems, and in May 1944 tests showed that a radial-engined version had about the same performance. (Philip Jarrett)

The Germans claimed that this was the first time the British had dive-bombed with 1600lb AP bombs. The post-war British analysis concluded that the 1600lb AP bombs were quite capable of penetrating the ship’s deck armour and causing vital damage and flooding if they were released from a sufficient height, and in sufficient numbers. That a dive bomber could deliver such a weapon effectively meant that the distinction between dive bombers, which in the past could destroy only lightly-armoured ships (including carriers), and torpedo bombers, which could sink capital ships, was being erased.

Had the bomb detonated, the main fire control rooms, switchboard rooms, etc would all have been put out of action, and flooding would probably have extended to the forward auxiliary boiler room. The German official report described the effect, had the bomb detonated, as ‘immeasurable’. Unfortunately, this one bomb failed to detonate. The Germans claimed that the bomb fuse had failed, but as they jettisoned the dud, details are lacking. There were always duds; had the attack force made more hits, some of the bombs would doubtless have exploded with devastating results.

The Germans and the Japanese seem to have become seriously interested in dive bombing at about the same time. The first dedicated German dive bomber design, the Heinkel He 50, was produced in modified form in Japan as the first Japanese naval dive bomber, the Aichi D1A1 (Type 94, hence adopted in 1934). The Germans went on to develop other types, most notably the Ju 87 Stuka. By 1941 the Imperial Japanese Navy had a high-performance monoplane dive bomber (D3A); its carrier groups included roughly equal numbers of dive and torpedo bombers.

The Royal Navy considered the arrival of German Stuka dive bombers in the Mediterranean late in 1940 a decisive factor which precluded operations in particular areas. Stukas had already shown their effectiveness at Dunkirk and in the Channel and the North Sea in 1940. The crutch under the belly could be adjusted to take either a 250kg or a 500kg bomb. Against merchant ships Stukas typically carried a 250kg bomb plus four underwing 25kg bombs; against cruisers and larger warships they used 500kg bombs (later they had a special 771kg armour-piercing bomb). Stukas typically approached a convoy from out of the sun at about 13,000ft at 150mph, releasing their bombs from about 1600ft in an 80° dive, and pulling out at about 700 to 800ft. Typically Stukas attacking large warships split up and dove simultaneously from different directions. Against destroyers a Stuka would typically approach from astern, as the pilot could more easily follow the ship’s evasive manoeuvres. That is why the Royal Navy emplaced destroyer automatic weapons, such as multiple pom-poms, so that they had wide aft arcs.

The Ju 87 ‘Stuka’ is remembered mainly for its service against land targets, but it was the most effective German air anti-ship weapon. (Philip Jarrett)

The successful 8 January 1941 Stuka attack against the armoured flight deck carrier HMS Illustrious profoundly affected the Royal Navy. Hitler had ordered Stukas to the Mediterranean in the autumn of 1940 as part of the larger plan to deploy the Afrika Korps in North Africa. His expectation was that by sinking the carrier (which they failed to do) the Stukas could tip the balance of sea power to the Italians and thus ensure successful sea support for the Afrika Korps. Although that was more than the Stukas could achieve, both the Royal Navy and Prime Minister Winston Churchill were shocked by the attack. The attack was carried out by forty-three Stukas attacking in three main waves, all approaching at 12,000ft. They checked their dives to correct aim at about 6000 to 8000ft before releasing bombs at 1500ft for the first wave and down to 800ft for later ones, which did not face such intense fire.

Most dove at 60°. At any one time about six Stukas were diving at the ship. German records showed four losses, one of them to a fighter. The fleet commander found this ‘novel’ type of attack so fascinating that he watched rather than being frightened. The Royal Navy claimed at the time that naval gunfire had brought three of them down (plus eleven probables), and that naval fighters had accounted for six more. German records showed four Stukas lost. The most important result of the March 1941 upset was the design of the ‘Battle’ class destroyers, with their all-dual purpose main batteries. This decision was reached before the destroyer massacre (by Stukas) off Crete in May 1941.

Churchill sent the Admiralty a personal minute in mid-March 1941 asking whether the Stuka had driven the Royal Navy out of the Central Mediterranean. He felt that the Admiralty had sent ships there with inadequate armament, and he wanted ships fitted with batteries of special anti-dive bomber weapons. A few days later a special meeting was convened to discuss possible countermeasures, including an apparently much-touted rocket (unrotated projectile [UP]) using a photoelectric (PE) proximity fuse. When ships first experienced dive bombing, personnel were bewildered by the spectacular nature of the attack. On the second occasion personnel were able to concentrate better, and on the third and later occasions they got the best out of their weapons. On this basis it seemed that Illustrious had fared better than most. It seemed that, given the massive scale of the attack, the worst problem was switching from one target to another quickly enough. The PE-fused rocket did not solve the problem, first because it had to be pointed properly, second because it fired too few weapons (and it might take two minutes to reload), and third because the fuze could function only under some sun conditions. Tests ashore had not taken the motion of the ship into account. At this time the LAM (Long Aerial Mine) was being developed for firing from a UP projector specifically to deal with night bombers (it took 40 seconds to establish itself). It was clearly not an anti-dive bomber weapon. The FAM, which was later widely deployed, was not a means of preventing a dive attack, because it was effective only after bomb release, but it might be an effective deterrent.

The meeting considered the pom-pom the most effective anti-dive bomber weapon; it would soon have high-velocity ammunition. Deployment of projected-wire rocket weapons was beginning. Thus 1100 ‘Pig Troughs’ (2in UP with contact fuses, four barrels) would be available by the end of April 1941, together with fifty ‘Pillar Boxes’ (20-barrel 2in UP) in June (and another 150 in July or August), plus 30 larger multiple UP mountings (twenty 3in barrels with PE fuses) by the end of May. A total of 26,000 FAM rockets were on order. Fifty Harvey projectors (PE-fused rockets) were being sent to sea for trials. There was also interest in fitting out the ex-French air target ship L’Impassible (14kts, 3in deck) with a large number of assorted UP weapons. The fleet’s existing larger-calibre UPs (Naval Wire Barrage) were not mentioned. At this time Formidable had been given seventy-five PAC outfits (rockets) mounted around her flight deck, but they do not seem to have been used in combat. Oerlikons were finally coming out of the British plant, and one proposal was to send them to the Mediterranean on an emergency basis on board long-range bombers and submarines (at this time all of them were assigned to defend merchant ships). There was also interest in a shuttle service for FAMs in the Mediterranean, ships cross-decking them when they reached port.

During the Second World War the United States developed toss-bombing, which might be thought of as an alternative way to use an aircraft to aim a bomb or other weapon (it was applied to rockets and even to torpedoes). If an aircraft releases a weapon in a climb, the weapon continues up and over. Using a computer which takes weapon ballistics into account, the aircraft can aim at a target without pointing directly at it, and thus can avoid anti-aircraft fire. The sight involved was called a bomb director, by analogy with a torpedo director.

Combined Tactics

The most effective attacks combined several different tactics, since measures to defeat one would open a ship to the others. For example, the Japanese made special efforts to co-ordinate different types of attack. The successful attack against Prince of Wales and Repulse combined high-level and torpedo bombers, both land-based. High-level bombers might not be all that effective, but they occupied channels of medium-calibre fire which might otherwise have been devoted to torpedo bombers. Japanese tactics reported in mid-1943 employed level bombing preceding torpedo and dive bombing attacks mainly as a distraction.³² On the other hand, the Japanese did not attack from different directors to overwhelm the defenders, because each individual aircraft had a relatively limited chance of hitting its target. Concentrating an attack gave the best chance of making some hits.

By 1943 the Japanese were also sometimes glide bombing at a 45° angle, beginning at about 12,000ft and releasing the bombs in level flight at 2500 or 3000ft. In ‘swing’ bombing, an aircraft flew towards the target until it reached the perimeter of anti-aircraft fire, then entered a banked turn and released a bomb which centrifugal force threw towards the target – a kind of toss-bombing. At this time the Japanese had not yet tried low-level anti-ship attacks, although they had certainly experienced such tactics.

Torpedo bombers generally approached at high altitude (to spot their targets at maximum range), reducing altitude and forming a loose string or wedge or diamond formation while still out of range. They attacked in multiples of three, most frequently nine aircraft. Dropping range was typically 1000–1500 yds and height was 35–300ft. Pilots aimed individually. After dropping aircraft did not violently evade fire, but rose heavily and departed slowly, passing close to the target. Torpedo attacks were often preceded by high-level bombing and followed by dive bombing.

Dive bombers typically approached in line, in sections of three aircraft or in vees of six to nine or vees of vees. They reformed into a loose echelon or string while still out of range, attempting to attack out of the sun. When they were covered by fighters, the latter were usually above and up-sun. Normally aircraft glided and dipped from about 18,000–14,000ft, gaining speed and position on the target in the process. The attackers were spaced at 3 to 4-second intervals, pushed over into 60–80° dives at 12,000ft or 13,000ft (in one report, at 9000ft), and releasing bombs while levelling off at about a 45° angle at 1000–2000ft. Aircraft lacked bomb-displacement gear (to throw the bomb clear of the propeller) and instead appeared to throw their bombs.

Strafing

Unlike a torpedo or a bomb, strafing using ordinary machine guns could not sink a ship. However, it could damage or destroy crucial installations, such as fire controls. As ships came to rely more heavily on electronics and on wiring between different parts of their combat systems, strafing gained importance. A series of three Japanese strafing attacks on a modern US destroyer on 1 October 1944 put it virtually out of action.³³ Three aircraft attacked, then two, then one. When the first attack developed, the ship was controlling one night fighter. A second was being controlled by an amphibious flagship (AGC) 20nm away, and a third was controlled by a shore base. The moon was full, the sky overcast, and surface visibility excellent. When the first attack was detected, the destroyer vectored her fighter to intercept, but that failed because the bogey vanished from the destroyer’s radar. The AGC took control of the interception. Her night fighter reported contact. As the contacts closed with the destroyer, the AGC ordered ‘Control Green’ to keep the destroyer from firing on the friendly fighter. At this time the destroyer had the bogeys on her radars and was tracking them and ready to open fire. The destroyer’s Combat Information Center (CIC) reported that the bogey had split, and that the night fighter was closing with one of the bogeys now evident. The fighter reported that his target was smoking. Immediately afterwards three aircraft made strafing passes which damaged the destroyer. Upon receiving the report of strafing the Officer in Tactical Command cancelled the Control Green order and the AGC night fighter was vectored away. The first attack destroyed fire-control power, leaving all guns in local control without any blind-fire capability. Unsurprisingly, later attacks were not seen until the aircraft opened fire and passed over the ship. The incident was blamed on an overzealous fighter director, who ignored the proximity of the picket destroyer, and also on the reluctance of the destroyer to take immediate aggressive AA action in the face of the Control Green order.

A heavy enough strafing gun could kill a ship. During the Second World War the United States mounted an automatic 75mm cannon on board some bombers, notably the B-25 (which the Marines operated as the PBJ).³⁴ This weapon sank at least a few ships.

Rocket attack might be considered the most extreme form of strafing. Rockets offered a good chance of hitting without subjecting an aircraft to the stress of dive or glide bombing. Both the United States and the United Kingdom deployed anti-ship rockets during the Second World War. For example, by late in the war Coastal Command Beaufighters, which attacked German convoys off the European coast, were armed both with rockets and with torpedoes. By about the same time many US fighters and attack aircraft were armed with rockets. Rockets offered the sort of accuracy usually associated with dive bombing, without the requirement for structural strength (to pull out of the dive) or the dive brakes associated with that kind of attack. They could also be delivered from a greater stand-off distance. On the other hand, they did not offer the sort of warhead weight a dive bomber could deliver. The US Navy sometimes claimed that the 5in Mighty Mouse rockets a fighter could deliver gave it the punch of a destroyer’s broadside. By 1944 there was also a much more powerful 11.75in rocket, Tiny Tim.

Guided Weapons

Towards the end of August 1943 the Germans introduced guided weapons which they hoped could be launched by a bomber effectively out of anti-aircraft range: the FX 1400 armour-piercing bomb and the Hs 293 rocket-boosted glide missile. FX 1400 was a guided armour-piercing bomb intended to attack capital ships and cruisers.³⁵ Both weapons were command-controlled, hence could be considered standoff weapons to be fired outside defensive range (Hs 293 was within extreme anti-aircraft range). Guidance was simple. The controller monitored the weapon by focussing on a flare in its tail. He tried to keep it moving in the same line as the bomber. To this extent the weapons could be seen as high-altitude bombs whose flight could be corrected for windage. To some extent the bomber could manoeuvre (like a dive bomber) to deal with target manoeuvres.

The Hs 293 was intended more to attack merchant ships and unarmoured warships. It had a 500kg bomb integrated into its airframe.³⁶ Radio control was exerted on its ailerons and elevators; there was no means of automatic height-keeping. The missile had a gyro autopilot. Because it was a small aircraft, Hs 293 could manoeuvre to some extent after being launched. A bomber typically carried two Hs-293 underwing. As of 1943 two modes of attack had been seen. In one, the bomber approached to within 3 to 5 miles of the target at a height of 3000–5000ft. Once the glider flew out satisfactorily, its controller turned it onto the line of sight to the target, the aircraft continuing on a steady course. The alternative was for the aircraft to approach in a conventional level bombing run at a similar altitude, then launch the glider when 3 to 4 miles from the target. When 3000–4000 yds from the target the control aircraft turned away, directing the missile down onto the target. During the Italian landings attacks were generally from the starboard side (presumably from ahead, as the aimer was on the starboard side of the aircraft and so kept the target to port).

FX 1400 (‘Fritz-X’) was a guided AP bomb. It offered the precision of dive-bombing without exposing the attacker to heavy close-range anti-aircraft fire, which the Germans predicted would ultimately make dive bombing impractical. Moreover, the bomb could be dropped from such a height that it would accelerate sufficiently to penetrate thick deck armour. This type of bomb sank the Italian battleship Roma. Note that successful conventional dive bombing with 1600lb AP bombs achieved the same sort of deck penetration against the Tirpitz. (Dr Raymond Cheung)

Both weapons enjoyed initial successes. The first Hs 293 attack was mounted against escort vessels in the Bay of Biscay, where they were blocking an important U-boat route. On the afternoon of 25 August 1943, twelve Do 217s attacked a group of eight escorts. None of them was equipped for long-range controlled AA fire. Of twelve Hs 293 launched, five went wild and the others made only near-misses. Two days later, however, a similar attack by eighteen Do 217s on five ships sank the sloop Egret and badly damage the destroyer Athabaskan. In this case only half the missiles remained on course.

The Germans then shifted their missile force to the Mediterranean to contest the invasion of Italy. On 29 August the fighter direction ship Ulster Queen and the small destroyer Cleveland were attacked using FX bombs, but neither was badly damaged; on 5 September the cruiser Orion was similarly missed. However, they were much more successful when the Germans used it against the Italian fleet steaming to Malta on 9 September. The battleship Italia was damaged and her sister Roma sunk.

Further attacks were made on the Allied fleet off Salerno between 11 and 17 September, some by FX 1400 and two using Hs 293. FX 1400s successfully hit the battleship Warspite and the cruisers Uganda and USS Savannah. Warspite was badly damaged and was never fully repaired (she managed to bombard Normandy beaches with only three of her four turrets, and with her machinery largely out of service). Savannah suffered a direct hit through a turret roof. She survived because her thin hull blew open in time to flood her magazine before it could explode. These were the last FX 1400 attacks.

On 30 September an Hs 293 attacking ships in harbour at Ajaccio sank an LST; another caused minor damage to a French destroyer. The missile was then used mainly against convoys (four dusk attacks), against a convoy in the Atlantic (by sixteen long range He 177s), and in moonlight in the Adriatic. The Atlantic attack sank a straggler and damaged another ship in the convoy, and the moonlight attacks scored two hits on destroyers but did not sink them. Hs 293s were used again in January 1944 off the Anzio beachhead, sinking the cruiser Spartan and damaging the destroyer Jervis; a US destroyer and a merchant ship were also damaged. It appears to have been used in Normandy.

The Royal Navy enjoyed some success in engaging the bombers which launched and guided Hs 293s using anti-aircraft guns. It promulgated a tactic in which a ship should turn as soon as the run-up to launch began to keep the launch bomber as far forward as ‘A’ arcs permitted. As the gliders approached, a ship should alter course to keep them ahead in the hope of making evasive turns. Presenting bow or stern would reduce the chance of a hit to a quarter of that expected by a ship presenting a beam aspect. Since the bomber relied on a continuous view of the target in order to guide the missile, smoke might successfully shield a convoy. Similarly, in the case of FX, long-range anti-aircraft fire could attempt to destroy the parent aircraft both before and after it dropped the bomb. Any evasive action should be toward the direction of attack, as it was easier for the bomb aimer to increase than to decrease the range of the bomb.

The Germans sometimes combined guided weapon attacks with more conventional ones: ships experienced synchronised attacks by Fw 190 fighter-bombers at low altitude while a Do 217 dropped FX from high level. They also tried a combination of Hs 293 and torpedo bombers against convoys.

Although in theory the best counter to missile attack was to use defending fighters to destroy the carrier aircraft, effort was concentrated on electronic countermeasures: receivers to detect the command signal and jammers to disrupt it. Jamming worked even though the antenna on the missile looked up or back at the guiding aircraft, rather than towards the jamming ship. For the longer term, both the Royal Navy and the US Navy began work on guided anti-aircraft missiles (in the US case, the Kamikaze threat spurred action). Both navies were uncomfortably aware that the Germans were operating at stand-off ranges at the outer limit of gun effectiveness (the maximum for a gun was probably 10,000 yds). The Soviets were sufficiently impressed to produce versions of both German weapons after the war.

Hs 293 was the first successful anti-ship guided missile. It may eventually have been defeated mainly by jamming. That it proved so difficult to shoot down inspired initial British and US naval air defence missile projects. After the war, the prospect of faster air-to-surface missiles doomed attempts to develop a new generation of close-range guns, as analysis showed that they were unlikely to be effective. The Royal Navy concluded that ships needed a short-range defensive anti-missile missile, which they called Popsy. This concept, which the Royal Navy was unable to fund, seems to have inspired US work on Tartar, the forerunner of the current Standard Missile. (Dr Raymond Cheung)

The United States mounted an aggressive guided-missile programme roughly in parallel to that of the Germans, but it produced only one operational anti-ship missile, Bat, which entered service in 1945. In contrast to the German missiles, Bat was self-guided using radar (hence the name, since bats home on their targets using echoes, in their case acoustic ones). Bat may have sunk one Japanese ship.³⁷

Kamikazes

The Pacific War counterpart to the German guided bombs was the Japanese Kamikaze, which was guided to its target by a human pilot. En masse they were much more difficult to counter, although each Kamikaze aircraft was an easier target than a small, fast German guided missile. German missiles were used in small numbers, because it took a special aircraft and crew to guide each one. Kamikazes were used in large numbers, because guidance was not a problem. They saturated every level of fleet anti-aircraft control, from fighter direction down to gun fire-control. This experience led to post-war interest in high-capacity combat control systems, ultimately using digital computers.

The Japanese began to consider suicide tactics after the disastrous ‘Turkey Shoot’ of June 1944, when their attack force was nearly annihilated by the fighters launched by Task Force 58. This episode was part of the battle for the Marianas, including Saipan. With the loss of Saipan, many in Japan considered the war lost, or at least that Japan itself was now open to attack. The government which had begun the war, headed by General Hideki Tojo, fell. Suicide attacks (or attacks with virtually no chance of survival) had long had a special place in Japanese thinking, which often emphasised the role of fighting spirit over technology. However, the systematic use of suicide tactics on a large scale, at least in air combat, was a new idea. For the Imperial Japanese Navy, it seems traceable directly to the experience of the battle of the Philippine Sea, the ‘Turkey Shoot’.³⁸

The US Bat was the first successful radar-guided anti-ship missile, guiding itself rather than relying on human commands (the name indicated the guidance technique: the missile homed on radar echoes, as a bat uses sonic echoes). (Norman Friedman)

Kamikazes were first encountered in the Philippines in October 1944. Later intelligence indicated that the tactic had been conceived after the Marianas ‘Turkey Shoot’ of June 1944 destroyed most of the Japanese carrier air arm. The logic was simple: the US Navy had become so efficient that any air attack against a US carrier task force was very nearly suicidal. Kamikazes offered a much better prospect for success. At this time combat air patrol (CAP) fighters were accounting for 60 per cent of attacking aircraft. As Kamikaze attacks continued, less experienced pilots were used, and in any case an aircraft heading directly for a ship was an easier target. By April 1945, 50 per cent of Kamikazes were being shot down without doing damage, compared to 33.6 per cent of conventional attackers – but massed anti-aircraft fire so ruined the aim of conventional attackers that they made only 10 per cent hits, compared to hits by all Kamikazes which survived defensive fire.

On this basis, a force of 300 aircraft would lose 180 to CAP, leaving 120 to attack the fleet. Of those, forty would be shot down by anti-aircraft fire, leaving eighty to attack, of which twelve might do significant damage. It would cost the Japanese 220 aircraft to secure twelve hits.³⁹ To get the same twelve hits would take only sixty Kamikazes. CAP would destroy the same proportion, in this case thirty-six aircraft, leaving twenty-four to attack the ships, of which twelve would be shot down. It would take only a fifth as many sorties to get the same results, and only 27 per cent as many pilots would be killed. To reduce enemy effectiveness to its previous level would be to require the enemy to fly out 220 aircraft (as many as would be lost in the conventional attack) to gain twelve hits. That would require CAP and anti-aircraft fire to destroy 208 aircraft, 95 per cent of the attacking force. A possible division suggested in April 1945 was for CAP to destroy 78 per cent of the attackers (172 aircraft) and AA 75 per cent (thirty-six aircraft). Stating such figures shows how difficult the problem was, once the Japanese were willing to make mass Kamikaze attacks.

The April 1945 figures explain elements of the anti-Kamikaze strategy. Strategic bombing of the Japanese aircraft industry was intended to cut down the supply of new Kamikaze aircraft. Given a limited supply, every attack on Japanese airfields cut the number of available aircraft. Although it was impossible to wipe out the entire supply of such aircraft, at the very least raids on the airfields could neutralise them temporarily. ‘Spikes’ and butterfly bombs could make it temporarily difficult to use airstrips. Most British Pacific Fleet strikes were directed against Japanese airstrips in hopes of limiting the overall Kamikaze threat. By August 1945 US planners contemplating an invasion of Kyushu that November thought that the Kamikaze threat had been considerably reduced in this way, but after the surrender it became clear that very large numbers of aircraft remained hidden, unused even in the urgent defence of Okinawa.

To US analysts, Kamikaze tactics were a natural outgrowth of three earlier types of Japanese tactics, beginning with the second year of the war. In 1943 the Japanese conducted simple, straightforward attacks. Typically they attacked only a few ships, often only one, at one time. Attacking aircraft flew more or less direct courses, and employed only moderate evasive tactics. There were many night attacks. Anti-aircraft fire was generally successful. Although some bombs and torpedoes struck, enemy air losses were high. The analysts did not say so, but these tactics were considerably less ambitious (and effective) than those employed during the first year of the war, in battles both at sea and in the Solomons, which killed most of the experienced aircrew with which the Imperial Navy began the war. Presumably the surviving experienced ones made the difficult night attacks.

In the second period, between January 1944 and June 1944, enemy aircraft were more cautious, and they used more evasive tactics. Meanwhile the US fleet was becoming more experienced, its anti-aircraft fire more effective. The Japanese were more wary in pressing home attacks. Their losses decreased. Few US ships were struck, and anti-aircraft fire was considered successful. The Japanese naval air forces were being husbanded to fight the expected decisive battle for Saipan.⁴⁰ Plans for that battle envisaged both a massive carrier air strike and shuttle-bombing by land-based naval aircraft. This period culminated in the disaster of the battle of the Philippine Sea and also in the piecemeal destruction of the land-based naval air arm which had been assigned the shuttle missions. The Japanese realised that conventional air attacks were unlikely to succeed – and that successive battles would be ever closer to Japan itself.

Between 1 June and 1 October 1944 the fast carrier task force struck repeatedly in the Central and South Pacific, first to win Saipan and then to deplete Japanese forces during the run-up to the invasion of the Philippines. In US eyes, during this period the Japanese generally made day attacks because the initiative rested with the United States. Enemy aircraft were even more evasive, and in many cases ships fired at aircraft which remained at ranges of more than 9000 yds without seriously attempting attacks. Anti-aircraft defence was highly successful. Again, the Japanese could be seen husbanding diminished resources for the next major battle. Aircraft remaining out of range were feeling out US task force defences. Later there was evidence that the Kamikaze attacks were conceived at this time.

Japanese plans for the defence of the Philippines included suicide attacks, which began in October.⁴¹ A British official account published in April 1945 described the initial attacks as long-awaited, presumably on the basis of intelligence. material. Kamikazes were accompanied by conventional attackers following the cautious tactics of the previous period.

The Japanese equivalent of the German guided bombs was the manned Okha, shown here surrounded by Americans to give an idea of its size. Unlike the German bombs, Okha was unjammable. On the other hand, it was no easier to control, and it had to be released in just the right place to have a good chance of hitting its target. (Philip Jarrett)

Initially Kamikazes were all aircraft of current combat types, typically carrying 250kg bombs (some carried 500kg bombs). Bombs were usually retained, but in some cases they were dropped before the crash. Usually aircraft also carried drop tanks, either to increase range or to increase fire damage. Most sinkings were caused by fire rather than explosion. These aircraft could not penetrate armoured decks, but they could cause great fire damage. Since US carriers had wooden flight decks (on thin steel plating), a Kamikaze could crash through into the hangar deck below. It could ignite gassed-up aircraft already loaded for strikes (big US rockets did considerable damage to a US carrier under these circumstances).

While the supply of existing aircraft was being run down, special Kamikaze aircraft were being built. Some were cheap wooden versions of existing types (one crude wooden aircraft was all-new), but there was also the rocket-propelled MXY-7 Ohka (‘Baka’) launched as a stand-off missile by a larger bomber.⁴² The first seen in combat were two launched at the destroyer Stanly while on picket duty on 14 April 1945. She splashed one, and the other clipped the flag on her after stack and blew up in the water. Both were hit repeatedly by 40mm fire. Another was launched by an army ‘Helen’ bomber off Okinawa on 18 April against the minesweeper Jeffers at a range of 14,000 yds from an altitude of 4000ft. It accelerated rapidly to 450kts on a course aimed straight at the ship. The missile was shot down by 20mm fire, hitting the water 50 yds on the port beam. ‘Baka’ attacks were always co-ordinated with conventional attacks. The destroyer Mannert L. Abele, on picket duty, splashed a ‘Val’ with the aid of LSM 189, which was assisting on her picket station. Then two ‘Zekes’ attacked. One was shot down, but the other hit her with a bomb, breaking her keel. Immediately afterwards a ‘Baka’ hit her starboard waterline. The destroyer broke in two and sank at once.

A survey of damage showed that carriers were always the primary targets, although the Japanese expended considerable effort attacking the destroyer pickets stationed between Okinawa and the fast carriers. Carriers were so large that a Kamikaze was almost certain to hit unless it suffered severe structural damage. Two of every three aircraft attacking carriers managed either a hit or a damaging near-miss. Overall, carriers were judged more susceptible to damage than any other type. Battleships were the most successful in destroying Kamikazes. The very low success rate of merchant ships indicated that in the late stages of an attack the target ship was its own primary defence – and that a determined suicide pilot would hit if not destroyed. Tabulated data showed that nearly 80 per cent of Kamikazes were killed not by proximity-fused 5in/38s but by automatic weapons (50 per cent by 40mm, 27 per cent by 20mm). In non-suicide attacks, 5in/38s were credited with 34 per cent of kills. Against Kamikazes, proximity fuses were responsible for 56 per cent of kills by 5in guns; in non-Kamikaze cases that was cut to 37 per cent. That was unfortunate, because 5in guns were the main hope of destroying Kamikazes far enough away that they could do no damage. Their poor performance was attributed to failure to open fire at maximum range, and also to failure to use a sufficient proportion of proximity-fused shells. The 5in guns did better against non-Kamikazes because they opened fire at longer range and they expended more ammunition, as they had more time to fire. Since many aircraft taken under fire never reached attack positions, the rising number of rounds fired per aircraft shot down was considered acceptable.⁴³

It was clear that the 40mm gun was the star of the anti-Kamikaze effort, and through 1945 the US Navy enormously increased the number of such weapons. The fleet was much less impressed with the 20mm, the general view being that it did its damage at such short range that a Kamikaze would often still crash into the ship. One destroyer officer wrote that the main value of the 20mm was as a warning: when they opened fire, it was time to evacuate machinery spaces. However, figures showed that the 20mm was still effective, and it was retained as far as possible.⁴⁴

Kamikaze tactics were not standardised, but all of that cautious probing before the Philippine Sea apparently taught the Japanese a great deal about how the US Navy used radar. The battle of the Philippine Sea itself taught them that inexperienced Kamikaze pilots should do whatever they could to avoid US fighters. Tactics could exploit both weaknesses of search radar (nulls at high altitude and limited capacity at low altitude) and difficulty in detecting targets overland; and weaknesses of the raid tracking and related fighter direction systems. For example, a CIC could track only a limited number of raids accurately enough for fighter control, so splitting up attackers could saturate a CIC.⁴⁵ As of March 1945, Kamikazes worked singly, or in formations of up to three; there was some slight evidence of co-operation by as many as six aircraft, but this was nothing like the numbers working together in conventional attacks. The Japanese also learned both to mimic US IFF and to trail US strike aircraft home. The latter tactic was so successful that special fighter sections (Tomcats) had to be assigned to examine home-bound formations visually and shoot down Japanese aircraft among them. Kamikazes were usually escorted by fighters.

Final attacks varied widely. By March 1945 there seemed to be five main alternatives. One was a near-vertical dive from high altitude, in effect a dive-bombing attack without a pull-out. A second was a low-level approach followed by a pop-up and a steep dive, to frustrate close-in fire.⁴⁶ A third was a shallow glide, from an altitude as great as 20,000ft. The British observed that this particular type of attack was difficult to engage by long-range armament. A fourth exploited the fact that ships’ anti-aircraft batteries were typically divided along the sides. An aircraft might approach from one side at low altitude, within close gun range, circle the ship, and attack from the other side. The commonest tactic was an attack along the centreline of the ship from astern by a single aircraft. It was easiest for the pilot to hit the ship, as he had the largest possible target, yet he faced the minimum number of anti-aircraft guns.

The Kamikazes emphasised the great difference between hitting the oncoming aircraft and demolishing it thoroughly enough that what was left of it would not badly damage a ship. This distinction applies to current anti-ship missiles.

Anti-Submarine Attack

Nearly all submarines had to charge batteries on the surface, and they could make good a reasonable distance only on the surface. They were reasonably invisible to any but the nearest surface ships, but they were easily seen from the air. The usual defence was a crash dive, but many First World War submarines could not dive very suddenly. For them an anti-aircraft gun might mean survival. In some navies submarines had more powerful anti-aircraft guns than most surface warships. Most Second World War submarines mounted a few heavy machine guns, but they relied mainly on crash dives. That was one reason US and Royal Navy submarines had air-search or air-warning radar. The Germans, however, lacked the necessary technology, and also feared that Allied antisubmarine aircraft might home on their radars. They tried to provide submarines with receivers which could pick up the emissions of Allied radars on board anti-submarine aircraft. The failure of this equipment led them to equip some U-boats, which they called ‘Flak U-boats’, with unusually powerful anti-aircraft batteries, with which they hoped to fight off air attacks. These weapons had no special fire-control equipment, and they proved ineffective. The ultimate defence against air attack was not to surface at all, which is why the Germans introduced the snorkel in 1944 (it bred a new kind of attack using sonobuoys and homing torpedoes).