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CHAPTER 2

Returning to Coercion

This chapter begins our analysis of war and technology with the changing nature of conflict in the twenty-first century. Even as technology in commerce and war is beginning to make revolutionary strides, the threat of major war is receding. The risks of great power conflict have declined since the massive destruction wrought by European nations in the nineteenth and twentieth centuries. Mankind is currently living through the longest period without a significant interstate war since the birth of the modern international system in 1648.¹ In the last seventy years, deaths from interstate wars have fallen by an entire order of magnitude from the rate of centuries before.²

But we are not entering utopia. Armed conflict remains a persistent feature of the human condition. Conventional or nuclear war between the great powers remains a considerable threat. After seizing part of Georgia in 2008 and annexing Crimea in 2014, Russia continues to destabilize Ukraine and harass NATO’s eastern borders.³ In the midst of a military modernization drive, China is building artificial islands to support its claims to all of the South China Sea, through which $5.3 trillion in trade passes every year. After eight years of retrenchment and withdrawal, the United States may well embark under President Donald Trump on a military buildup and a reinvigorated foreign policy.

In the past, some wars between great powers were almost amicable. Regular armies could settle the dispute on the battlefield, far from civilian population centers, almost in the manner of a duel. In 1866, for example, Prussia provoked a war with the neighboring Habsburg Empire. Prussian forces quickly prevailed at the Battle of Koniggratz. Chancellor Otto von Bismarck restrained Prussian generals from trying to capture Vienna, and instead negotiated peace terms that limited Austrian losses.⁴ Within a dozen years, the two powers entered into an enduring alliance. When war was not absolute and surrender was not unconditional, conflict focused on disabling military capacities until one nation accepted the political goals of the other.

Of course, some conflicts followed a very different pattern. In the Second World War, Germany did not surrender until Allied armies had seized every one of its major cities, sometimes only after grinding urban combat. Allied armies had to prove beyond dispute that they could assert control over all parts of Germany. But victory does not always go to the side with more troops or better weapons. A guerrilla war can become a contest of willpower rather than weaponry. After eight years of struggle, the French abandoned Algeria in 1962, not because of the incapacity of the French army, but because the French public would no longer support the military effort.⁵ Eight years of struggle was not too much for the leaders of the Arab National Liberation Front, but it was too much for France.

Other challenges to peace come not from Soviet tanks pouring into West Germany, but from regional revanchists, authoritarian regimes, and terrorist groups. In this new century, civil wars, such as the one that has killed or displaced millions in Syria and Iraq, or conflicts in lands where the West has few interests, such as those in Sudan or Congo, have caused enormous death and suffering. Future killing may come at the hands of rogue nations, such as North Korea or Iran, that come into possession of weapons of mass destruction. Or deaths will flow from terrorist groups, such as al-Qaeda or ISIS, which operate with global reach and can wield violence once only in the hands of nations.

In this new world of security threats, the great powers will not need agreements to ban their latest weapons. They are likely to deter each other from destructive attacks, just as mutually assured destruction kept the Cold War from turning hot. Instead, the greater threat is that the great nations will be loath to intervene against rogue nations or terrorist groups, who employ unconventional methods to coerce the West. The United States and its allies will never be able to match these enemies in their willingness to descend into barbarism. Instead, we must exploit our advantages in cyber and robotics, our control of the air, seas, and space, and our ability to integrate information processing, computers, and soldiers. Drones, cyber weapons, and precision-guided missiles could give the West the ability to kill terrorist leaders, cripple an authoritarian regime’s infrastructure, or destroy clandestine WMD research facilities. These technologies and skills could allow the great powers to use force more precisely and swiftly to prevent the rising threats of the twenty-first century from upending the international order.

Critics worry that the spread of these new weapons will lower the barriers to war. If launching a drone or activating a cyber weapon becomes too cheap and easy, they warn, nations will resort to force far more readily than today. But this earlier, more precise use of force could prevent threats from metastasizing into far worse dangers. It could even have a salutary effect in further dampening the risks of great power war. As we will show, war often breaks out between nations because they cannot overcome the informational and commitment obstacles to bargaining. Because of the anarchic state of the world, nations in a dispute cannot gather credible information about the capabilities and desires of their rivals and they cannot trust them to keep their promises. Cyber and robotic weapons give nations not only greater ability to coerce each other, but also more means to communicate their intentions in war and their reliability in peace. With these weapons available, we should see nations settle more disputes by negotiation, rather than by escalation.

We do not mean to argue that more advanced technologies will now transform the battlefield and ensure that future conflicts will always be won by the side with the better weapons. In the early twentieth century, for example, air-power enthusiasts argued that bombing could replace ground assaults. Colonial powers used air attacks in the interwar period, notably the British in Iraq and Spanish forces in Morocco. But command of the air did not ensure French victory in Algeria in the 1950s, nor Soviet victory against Afghan guerrillas in the 1980s. War is unpredictable because, in the end, it is a contest between human hearts and brains, not a duel of gadgets. The side with the more advanced weapons may not be the side with the most commitment in a long struggle.

This chapter proceeds in three parts. Part I will describe the new security challenges of the twenty-first century. It will explain that the nature of these civil wars, rogue states, and terrorist groups requires more widespread, albeit less destructive, uses of force to police them. Part II will explore how new weapons technologies, and a modern understanding of the tactics and strategy to take advantage of them, can lead to less rather than more conflict between the major powers. Part III will criticize the current rules of the U.N. Charter, which might deter states from using new weapons to confront these new threats. While the twentieth century’s threats are receding, the instability and disorder of the twenty-first may require the great powers to use force more often, not less.

New Security Challenges for the Twenty-First Century

In August of 2013, the White House acknowledged clear evidence that the Syrian army had used chemical weapons, despite firm warnings from President Barack Obama against using such munitions.⁶ The White House tried to mobilize support for retaliatory military action by western countries, including France and Great Britain. In the ensuing debate, some critics warned against costly entanglement in the ongoing civil war in Syria. Others worried that outside intervention might allow rebel forces to install a dangerous Islamist government. Some believed that western strikes might escalate the conflict and spread the fighting beyond Syria to neighboring countries, such as Turkey, Lebanon, Iraq, and Israel.

Almost no one opposed retaliatory air strikes on the grounds that intervention, in itself, would run contrary to international norms. The Chemical Weapons Convention prohibits the production, stockpiling, and use of chemical weapons, such as sarin and VX nerve gas.⁷ But it does not authorize the use of force against violators; it only empowers states to refer a situation to the U.N. Security Council. In any case, Syria never signed the CWC. The U.N. Charter empowers the Security Council to authorize the use of force to protect against threats to international peace and security, for which the Syrian civil war or the use of chemical weapons might qualify. Despite pressure from the United States, Britain, and France, however, the Security Council could not act because of the vetoes of Russia and China.⁸

It was hard to see the Obama administration’s proposal as anything other than “punishment.” The White House denied that intervention would aim at influencing the outcome of the civil war.⁹ The announced goal was to “impose a price” for using such terrible weapons, or, in more direct terms, to “punish” the Assad regime. The administration did not propose air strikes to destroy the chemical weapons stockpiles or their production facilities. The aim was simply to impose some “cost” elsewhere to deter future use of the weapons. Critics warned that the tactic would prove ineffective or have unacceptable side effects, but not that it was, in itself, improper.¹⁰ The Obama administration finally embraced an alternate policy, an agreement with the Syrian and Russian governments for the internationally supervised removal of the chemical weapons.¹¹ Administration spokesmen insisted, however, that this outcome had only been possible because it had previously threatened Syria with punitive strikes.¹²

The Obama administration’s approach to Syria predictably failed. Syria continued its brutal civil war that has killed an estimated 470,000 people, most of them civilians.¹³ The Assad regime continues to use chemical weapons, though perhaps not in the amounts that it would have without the agreement. The remaining Syrian population that could flee has left the country. According to some estimates, more than four million Syrians have become refugees, destabilizing the region and pressuring even NATO allies.¹⁴ In the power vacuum left by withdrawing U.S. forces in Iraq, al-Qaeda transformed into ISIS and seized large swaths of territory in both countries. ISIS has imposed a draconian version of Sharia law on the people under its control and created a safe haven where it can train new fighters from around the world. Along with the United States, Turkey has declared that the Assad regime must go and has crossed the border in force to root out ISIS. Meanwhile, Russia and Iran have sent unconventional fighters, regular troops, and modern air power to prop up the Assad regime.

The Syrian civil war illustrates the threats to peace in the twenty-first century, which now come less from great power war and more from rogue nations, terrorist groups, and failing states. Though the threat of general war has receded, these new challenges may demand that states use force more often, but at lower levels of intensity. Civil wars and humanitarian crises, however, may deter intervention because of the possibility of high casualties in urban environments. Terrorists and guerrillas refuse to follow the laws of war by refusing to distinguish themselves from civilians, hiding among them, and launching terror attacks on them. WMD and rogue nations present further difficulties because of the covert nature of their weapons programs and their disregard for the lives of their own civilians. Left to fester, these challenges can grow into serious threats to international stability, whether from terrorist attacks, the deaths of thousands of civilians, or authoritarian regimes armed with nuclear weapons. New technologies can help the great powers address these threats by applying force with greater precision at less cost.

Preemption and WMD Threats

Weapons of mass destruction pose new challenges. Widespread destruction has always been a possibility in war. In ancient times, the civilized states of Greece and Rome sometimes massacred or deported all the inhabitants of an enemy city. But before the twentieth century, the possibility for casualties had not reached millions from a single strike. A hostile army also had to invade enemy territory before it could slay and destroy. Now nuclear weapons can wreak devastation in the first minutes of conflict and, if widely used, destroy most human life on earth. Even the detonation of a single nuclear weapon in the United States could kill vast numbers of people and severely disrupt our society. Nations have an interest in keeping these most destructive weapons out of the hands of the most reckless leaders, especially those who might use them impulsively or share them with terrorists.

It is not unusual for a sudden change in arms to generate a strategic threat. In such circumstances, western leaders once thought that they could act preemptively before such a threat had matured, even before an attack was “imminent.” In 1807, for example, Great Britain feared that Denmark and Norway would transfer their fleets to France, which would have allowed France to challenge the Royal Navy’s control of the seas. Instead, after the Danes refused to hand their fleet over to the British, a British fleet bombarded Copenhagen for three days. The Danes changed their minds and gave up their fleet. The British government defended this intervention against a neutral nation as an act of “self-defence.”¹⁵ Great Britain took similar action in July 1940, after France had signed an armistice with Germany. Churchill ordered an attack on the French fleet in North Africa to prevent its transfer to German control. Most observers did not condemn this vivid demonstration of Britain’s determination to go on fighting.¹⁶

But modern weapons have multiplied the destructiveness of attacks while accelerating their speed and surprise. To be sure, it may still take weeks, or months, to put a conventional armed attack in motion. The United States required months to assemble the invasion forces in the Persian Gulf War of 1990 and the Iraq war of 2003. But stealth bombers, hypersonic cruise missiles, and ballistic missiles have reduced the time for an attack to be detected, not to mention stopped. A ballistic missile can drop a nuclear warhead on a city in thirty minutes.¹⁷ Ballistic missile technology has even spread beyond the arsenals of the great powers to rogue nations like Iran and North Korea.

Nuclear weapons threaten a magnitude of destruction that goes well beyond the transfer of a fleet in the nineteenth or twentieth centuries. They could cause devastating and indiscriminate long-term damage to the civilian population and the environment. A single five-megaton nuclear blast, for example, would generate a 2.8-mile-wide fireball, heat of 14,000 degrees Fahrenheit (the sun is 11,000 degrees F), winds ten times stronger than a hurricane, a ground shock 250 times worse than any earthquake, and air overpressure of 500 pounds per square inch.¹⁸ In 1996, the International Court of Justice observed that such weapons possess unique characteristics, “in particular their destructive capacity, their capacity to cause untold human suffering, and their ability to cause damage to generations to come.”¹⁹ The spread of ballistic missile technology and advances in miniaturization have allowed even Third World nations to develop the capacity to launch nuclear attacks with little warning. The magnitude of harm threatened by WMD has grown, their detection has become more difficult, and the time necessary for their launch has dropped.

The calculus of war must shift to meet these technological developments. In order to prevent the possible use of WMD, nations should resort to force earlier depending on the nature of the threat. As many scholars and international tribunals have read the U.N. Charter, nations are now prohibited from using force except in two situations: in response to “an armed attack” or by authorization of the U.N. Security Council. On the other hand, most scholars acknowledge that nations may launch attacks to preempt an imminent attack before an enemy has crossed the border.²⁰ In the famous case of the Caroline, in which British forces pursued Canadian rebels across the U.S. border, Daniel Webster argued a nation could use force in anticipation of an attack that is “instant, overwhelming, leaving no choice of means, and no moment for deliberation.”²¹ The Caroline test, which the Nuremburg tribunal and the ICJ Nicaragua decision attempted to elevate to the status of universal customary law, appears to create a high bar for the use of force. But it also contains the seeds of a broader understanding of war more appropriate to today’s world.

Caroline’s imminence test placed its emphasis on timing because of the nature of early nineteenth-century weaponry. Fleets and armies moved slowly, their weapons engaged at short range, and they relied on primitive munitions. An enemy nation could not inflict crippling losses in a surprise attack. Nations could afford to wait until an attack became more certain because the risk of destruction was not great. A large-scale invasion would reveal itself because of the preparations involved. Even by the time of World War I, the European great powers required several weeks to mobilize their massive armies, as Barbara Tuchman vividly described in The Guns of August.²² The Caroline test seems much less compelling when the threat comes from a hostile state intent on acquiring WMD and the means to deliver them quickly. To wait for peaceful resolution may mean waiting until the target state has already passed the nuclear threshold. It would be vastly more dangerous to take preemptive action against a state that has already acquired nuclear weapons.

In the face of such change, self-defense must expand beyond temporal imminence. Technological advance has increased the destructiveness of modern weapons, while making them harder to detect, quicker to launch, and cheaper to build. Nations should have the ability to use force even earlier than in the Caroline test, which involved a dispute between two friendly nations with armies and navies propelled by horses and sail and armed with cannons and muskets. Even if the probability of an attack has declined, the increase in magnitude must mean that nations can use force earlier to forestall it.

The Cuban Missile Crisis demonstrates the workings of such an approach. Moscow’s secret deployment of medium-range nuclear missiles only ninety miles from the U.S. posed a threat to American national security and would have upended the balance of power. While the Soviets were transporting missile components by ship, it appeared that they had neither fully assembled nor fueled the weapons. No attack was imminent in a temporal sense. Nonetheless, President John F. Kennedy ordered a naval “quarantine” on Soviet shipments to Cuba—a use of force that blocked navigation around Cuba and threatened the boarding and detention of Russian ships and crew. He argued that Nikita Khrushchev’s dispatch of the missiles “add[ed] to an already clear and present danger” because “we no longer live in a world where only the actual firing of weapons represents a sufficient challenge to a nation’s security to constitute maximum peril.” He emphasized that the speed and harm of modern weaponry justified earlier action. “Nuclear weapons are so destructive and ballistic missiles are so swift, that any substantially increased possibility of their use . . . may well be regarded as a definite threat to peace.”²³ While scholars at the time debated whether the quarantine violated the Caroline test,²⁴ Kennedy’s measured use of force brought the crisis to an end and was JFK’s finest moment in office.

The Cuban Missile Crisis also illustrates the promise of more precise uses of force that new weapons make possible. Khrushchev’s deployment brought parts of the U.S. within fast striking range of Soviet nuclear missiles for the first time. The United States did not wait until an attack was imminent to destroy the missiles and launch sites, which could have produced an escalation that led to a broader war. Instead, the United States imposed a blockade that used force in a narrower, less destructive manner, but still rendered it difficult for the Soviets to complete and launch the missiles. The potential harm from a Soviet attack was lower at this earlier point in time, because even though the potential magnitude of destruction from a nuclear attack was still great, there was a much lower probability of it. That expected harm was still high enough—it might even be tantamount to an imminent threat of a less destructive conventional attack—to justify a resort to force. In order to act earlier, however, the United States employed less violent methods than that justified by an imminent attack. Because the expected harm of an attack was lower (due to its greater uncertainty), Kennedy appropriately used more precise, less harmful means to coerce the Soviet Union to withdraw its missiles.

Preemption looks different when the threat is not so much an immediate attack as a sudden, menacing advance in enemy capacity. That was the threat from Iraq’s nuclear program in the early 1980s. Israel launched an air attack on the Osirak nuclear reactor in 1981 because it believed that Baghdad was creating the components for nuclear weapons. An Iraqi nuclear attack on Israel would have catastrophic consequences, but no such attack could occur until some years into the future. Iraq had not recently attacked Israel, though it maintained its opposition to Israel’s existence.²⁵ Israel acted before the reactor became operational to take advantage of a window of opportunity that would soon close. A later attack could have released radioactive fallout over Baghdad. The U.N. Security Council condemned the attack as a “clear violation of the Charter of the United Nations and the norms of international conduct.”²⁶ Even the United States, which had traditionally protected Israel with its Security Council veto, voted against Jerusalem and condemned the attack.

At the time, Iraq appeared to be complying with its international obligations for its civilian nuclear program, had not attacked Israel or Kuwait, and seemed preoccupied with its ongoing war against next-door Iran. Still, Israel had the better of the argument. Its ambassador to the U.N. responded that to “assert the applicability of the Caroline principles to a State confronted with the threat of nuclear destruction would be an emasculation of that State’s inherent and natural right of self-defense.”²⁷ Despite his assurances to the contrary, Saddam Hussein continued to pursue WMD and was on his way to a nuclear weapon by the time of the 1991 Persian Gulf War. He had a hostile intent not just against Israel, but Iran to the east and Kuwait to the south. If Saddam had developed nuclear weapons by the time of the 1991 war, U.S. forces would not have succeeded so easily in dislodging Iraqi forces from Kuwait.

New weapons can make such interventions safer or more feasible to pursue. Beginning in the late 1990s, the United States protested efforts by Iran to secure a reserve of weapons-grade uranium fuel that could be used for nuclear weapons. Successive administrations seem to have cautioned Israel not to launch its own air attack on Iranian nuclear facilities, lest this provoke a dangerous level of conflict in the Middle East at a time when Iran was already supporting Shia militia in Lebanon and, after 2003, in Iraq.²⁸ Instead, the United States launched an elaborate cyber attack on the Iranian nuclear program. Stuxnet may have set back the Iranian program for a few years without causing any direct injury to human beings. It is not certain that bombardment from the air could have done better, and it more likely would have caused more casualties. Iran no doubt would claim many of the deaths were civilian, since it has always insisted that its nuclear program was for peaceful purposes. Nevertheless, Stuxnet might have created the conditions for more favorable terms in subsequent negotiations. In its eagerness for a deal, however, the Obama administration seemed to have forfeited the leverage provided by the cyber attack.

The cyber attack might have worked longer-lasting harm to Iran’s uranium processing equipment. The Iranians could see that centrifuges were malfunctioning and had to be replaced, but they did not learn the cause for some time.²⁹ The United States government did not acknowledge its role in developing or infiltrating the computer codes that caused the damage. Ambiguity about the source of the attacks may have made the intervention less provocative and confrontational compared with an air strike. The uncertainties made it easier for both sides to avoid immediate charges and countercharges and an escalation of hostilities. Officials in the Bush and Obama administrations understood that a stealthy cyber attack on the Iranian program would be less threatening to the Iranian regime.³⁰

Critics will claim that these new weapons will make unilateral intervention too attractive. Their very ease, precision, and light impact will encourage nations to resort to force in lesser or more highly focused increments. Bombing a city or landing thousands of troops will challenge a nation’s sovereignty and spark demands for a military response. But a highly focused attack with specialized technology, which does little direct injury to civilian life, may give nations the flexibility to respond with diplomatic protests and a peaceful resolution.

It may be that new technologies will encourage an overly complacent attitude toward preemptive or preventive attacks. Still, we must balance this risk against the risks involved when states remain passive while WMD fall into reckless or threatening hands. Western nations may best counter the ambitions of an Iran or North Korea with high-tech weapons, which might force rogue states to the negotiating table. There may be no easy way to prevent a state from acquiring WMD. We might slow down Iran with attacks on its research facilities or its supplies of uranium, but it could turn to new, even more covert avenues to seek WMD. Western nations must use their new weapons to send a clear political message that Iran, its nuclear facilities, and its scientists are vulnerable to both conventional and covert attacks.

Syria demonstrates the limits of military strikes, whether using conventional or new weapons. Even though the Obama administration threatened strikes against the Assad regime for its use of chemical weapons, it also worried that destroying the stockpiles might pose great risk to civilians. While the Obama administration accepted Russia’s face-saving compromise to remove the Syrian stockpile, western intelligence agencies have reported that the Assad regime subsequently used poison gas in its campaign against rebels.³¹ The U.S. seemed particularly helpless because it could not reasonably threaten force. President Obama vaguely threatened air attacks, but could not identify any targets while ruling out any ground troops.³² A strike on WMD facilities might trigger a release on nearby civilians, while hitting Syrian military facilities might violate AP I, since the U.S. and Syria were not yet at war and the U.S. would have no right to destroy Syrian military capacity.

The problem goes beyond the immediate impact of a punitive strike on a rogue nation’s WMD capabilities. The Syrian government denied, dissembled, and then returned to using its weapons on both rebels and civilians. A U.S. strike would need to carry the threat of significant destruction and future repetition to deter Syria, in order to intimidate rather than incapacitate. New weapons provide opportunities for imposing coercive pressure by destroying an enemy’s WMD assets, but that may not always be feasible or sensible. It does not follow that every use of new technology must pass muster with psychological warfare experts or grand strategists. But new opportunities will reconfigure the terms of conflict. One of the best reasons for accepting the new risks of new weapons may be reducing the spread of even worse weapons. It is hardly the only application worth thinking about.

Humanitarian Intervention

In 1994, ethnic Hutus murdered nearly a million Tutsi civilians in Rwanda. The word genocide, much abused, was coined to describe horror on that scale. Due to past violence between Tutsis and Hutus, U.N. peacekeepers had already deployed to Rwanda before the murderous campaign. They were promptly withdrawn for fear that an attack on them might entangle their home states (Belgium and Canada) in the conflict. The carnage ended when a Tutsi army, mobilized in neighboring Uganda, invaded Rwanda and overthrew the Hutu government.

There was much soul-searching in the aftermath. President Clinton described the failure to act in Rwanda as the worst failing of his presidency.³³ But landlocked Rwanda was not within easy reach of significant western forces. Scholars have disputed how easily the United States or other outside powers could actually have sent ground forces to stop the genocide and whether they were prepared for a long-term commitment. Other African civil wars have yielded even higher death tolls without interference from outside; Sudan’s wars have killed 2 million, while Congo has lost 1.75 million.³⁴

Five years later, the Clinton administration took the lead in mobilizing a NATO intervention to protect the threatened ethnic Albanian population in the Kosovo province of the former Yugoslavia. It feared that an intensification of the conflict between Kosovars and Serbia could lead to genocide. Regrets about Rwanda may have strengthened calls for western intervention, but the terms of intervention also underscored the limits of western willingness to act for humanitarian reasons. To enforce its demands for the withdrawal of Serb military forces from Kosovo, NATO initiated a bombing campaign that lasted ten weeks. NATO planes operated above 15,000 feet to place them beyond the reach of Serbian anti-aircraft defenses. There were no NATO casualties. There was no evidence of genocide or mass murder when international investigators gathered evidence for war crimes charges after Serbia withdrew. A U.N.-sponsored occupation of Kosovo has encouraged claims for independence but has yet to secure international agreement on the division.

An intervening state may claim that it acts solely from “humanitarian” concerns while other states may reject that claim. A democratic state that insists that its intervention has purely good motives may still stir concerns among its own people about the risks and costs. There are always good reasons to be cautious about projecting force into a conflict zone without immediate strategic value. Nevertheless, Rwanda and Kosovo illustrate the challenge to international stability from conflict within, rather than between, states. Since the end of World War II, about two-thirds to three-quarters of all wars have occurred only within one state.³⁵ One study estimates that civil wars account for about 80 percent of all deaths from armed conflict since 1945.³⁶ Another study reports that about 90 percent of postwar casualties are civilians.³⁷ Civil wars cause far more casualties and last on average far longer (six years versus three months) than interstate wars.³⁸

These deaths primarily occur today in failed states. While scholars disagree about the precise definition of a failed state, the concept first described the successor states of the former Yugoslavia and African nations beset by civil wars after the end of the Cold War. Superpower competition had kept some of these nations afloat, thanks to aid from the U.S. or the U.S.S.R., while autocratic governments had kept others from breaking out into ethnic conflict. Failed states arise where government institutions no longer exercise effective authority, the economy has collapsed, and private groups control resources and population and rival the government.³⁹ States without an effective government may provide terrorists or criminal groups with a safe haven from which to recruit and train fighters, organize their arms and finances, and ship money, personnel, and weapons. Somalia’s collapse, for example, not only allowed tribal warlords to divide the country, but it also became a breeding ground for the al-Shabaab terrorist group and other militant extremists. Afghanistan allowed al-Qaeda to operate freely and to plan and launch the 9/11 attacks.

Western interventions often sought to end ethnic strife and create stable governments in areas of little strategic importance. In Somalia and Haiti, for example, the United States sent troops to stop mass suffering and to establish stable governments. From a realist perspective, these actions delivered little benefit to the United States. Somalia had little strategic importance, few resources, and had already suffered through years of civil war. A poor country with few economic resources, Haiti had greater significance because of the potential refugee flows to American shores. Unlike Somalia and more like Haiti, Kosovo involved some security interests, but those of America’s NATO allies rather than those of the United States. The United States certainly faced no threat of attack from Serbia, nor did it have any important strategic or economic interests in the Balkans at the time. In these cases, war served as a tool to combat threats to regional stability rather than as a means for unchallenged control.

The 2011 Libyan conflict provides another example of the challenge posed by failed states. Libya posed little threat to the United States or its forces abroad. Dictator Muammar Gaddafi kept his military deliberately small, limited to about 50,000 troops despite Libya’s large oil revenues, to avoid a military coup. After the U.S. invasion of Iraq in 2003, Libya had voluntarily given up its nuclear weapons program, compensated victims of its terrorism, and normalized relations with the West. In February 2011, the Arab spring movement reached Libya. Gaddafi ordered the Libyan military and security services to fire on demonstrators, sparking a civil war. Rebels quickly freed the eastern half of the country and established their headquarters in Benghazi, but suffered a turnabout in their fortunes. After several weeks of indecision, the United States and its allies intervened when Gaddafi’s forces threatened to snuff out the rebellion. The West had no desire to seize Libya’s oil or territory. Instead, as President Obama said in March 2010, “Gaddafi must go” for wantonly killing Libyan civilians.⁴⁰ The West resorted to force not because Libya posed any imminent threat to its neighbors, but because of a civil war against Gaddafi’s rule.

There may have been more at stake in Libya than just humanitarian considerations. Before the conflict broke out, Libya pumped 1.6 million barrels of oil per day—2 percent of global consumption—making it the seventeenth largest oil producer in the world.⁴¹ Libya exported 85 percent of its daily production to Europe. Notably, NATO did not send its troops to other conflicts, such as those raging in Africa where the loss of life was as high or higher than in Libya but where there is little oil. However, if securing Libya’s oil were the only goal, the United States and its allies intervened at precisely the wrong moment. It is more likely that European nations were concerned about instability so close to their shores, which might generate a flood of refugees headed for the European Union. However, by waiting so long to intervene, and acting so ineffectively, European nations ended up setting off the very stream of refugees that they feared.

Instead, the Libyan war bears similarities in motive to earlier postwar interventions. Haiti, Somalia, Afghanistan, Iraq, and even the former Yugoslavia did not raise the prospect of nation-state war of the kind that characterized the nineteenth and twentieth centuries. Aside from Iraq in 1991, which posed a threat to Kuwait, Saudi Arabia, and perhaps Israel, these countries did not menace their neighbors with aggression. Instead, they threatened the international system because of the internal conduct of their regimes.

Quite a few legal commentators argued, in the wake of the Kosovo intervention, that international law does not authorize resorting to war, even for humanitarian purposes.⁴² The U.N. Charter allows military force in “self-defense,” which can include aiding another state under attack.⁴³ But, according to many commentators, the Charter does not authorize outside states to deploy force to protect a threatened minority population against its own government. That reading of international law will be less compelling, however, if intervention becomes less costly, both for the intervening power and the targeted state. Drones might identify and disable the military units, either on the side of the government or rebels, in a civil war. They could destroy transportation used to carry prisoners and their detention camps too. They could compile detailed views of relevant sites, which might then come under scrutiny by international inspections. Cyber attacks might be used to disable broadcasting and social media, such as the radio broadcasts that incited the massacres in Rwanda.

New technology will make it easier to intervene to stop humanitarian disasters, but these options will not always render intervention effective or wise. What is stopped at one point may resume at a later time. What does not happen may not have happened. Outside states cannot intervene every time civilians are at risk of terrible violence. Premature or ill-judged intervention may even trigger hostile responses from local populations or goad outside powers to intervene. Technology won’t supplant the need for judgment, but it will make it much harder to claim an inability to use force.

Technology will also erode rules that seek to limit the focus of interventions. In the 1990s, some critics questioned why Britain or the United States had not bombed rail lines leading to Nazi death camps during the Second World War. A considerable debate ensued on whether such action was feasible and whether it would actually have saved many lives.⁴⁴ Yet, as a contemporary European scholar has noted, AP I would now prohibit such action, because interfering with the operations of a concentration camp would not offer a “definite military advantage” to the attacker (as required by AP I’s definition of legitimate “military objectives”).⁴⁵ When there is a chance to save lives by ignoring the AP I rules, responsible governments will find it easy to bend those rules.

A cramped view of the right of nations to intervene for humanitarian purposes will likely fail if new weapon systems prove their value in preventing catastrophes. Their primary value may not be physically disabling the instruments of mass persecution but in making clear that leading nations may intervene to prevent such horrors. Using force can be as important for its political or psychological impact as its immediate physical effects. If new weapons can act as a warning or a marker, nations will not limit their use to extreme humanitarian crises.

Terrorism

Terrorist groups unconnected with any one nation-state, but nurtured in the ungoverned territories of failed states, present yet another security threat. The defining characteristic of terrorists is their lack of allegiance to any nation. The September 11, 2001 hijackers, for example, launched their attacks as part of the al-Qaeda network of Islamic radicals. Several were from Saudi Arabia, one of the U.S.’s oldest allies in the Middle East. Though they operated from a safe haven in Afghanistan, the hijackers had no defined territory, cities, or people to defend. They received funds from private and religious charities and drew manpower from a pool of disaffected, alienated, or unemployed young men bitter over the Arab world’s decline.

Instead of common ethnic or local origins, al-Qaeda members are unified by an Islamist-inspired desire to engineer fundamental political and social change in the Middle East. They seethe at the rise of the Christian West, the collapse of the historic caliphate, the presence of American troops in the region, and the corruption of Arab regimes. To them, the United States is the primary cause of the conflicts and reversals suffered by the Islamic world. They believe that attacks on the U.S. will convince it to withdraw from the Middle East and cease support of existing Arab governments. Victory for al-Qaeda does not involve defeating U.S. military forces and negotiating a peace settlement, but demoralizing an enemy’s society and coercing it to follow its political goals.

Terrorism depends on unpredictable, sporadic, and quick strikes on civilians using unconventional methods. The 9/11 hijackers wore no uniforms, did not operate in regular units, nor did they carry their arms openly, as required by the customary rules of warfare. Terrorist networks organize their personnel, materials, and leadership into covert cells, which can operate overseas or within the United States itself. While these features may have been present with other groups for many decades, new channels of global commerce and transportation have given terrorists more effective means to organize, finance, and move operatives into positions for attack. These new technologies allow terrorist groups to strike from half the world away with a destructive power that only nations once could exert. Few nations could have duplicated the September 11, 2001 leveling of the World Trade Center in New York City and the attack on the Pentagon using conventional weapons alone.

ISIS’s rise has expanded the terrorist threat beyond the high-casualty, spectacular attacks that were al-Qaeda’s hallmark. ISIS enjoys some of the attributes of a state. It seized territory in Syria and Iraq in 2014, including the major city of Mosul. It controls population, at one time reaching to several million people, and considerable resources within that territory.⁴⁶ It performs some government functions, such as a justice system that enforces its interpretation of Sharia law (however barbaric), taxation, and welfare services. On the other hand, it does not conduct diplomatic relations, nor does it seem capable or interested in upholding its responsibilities under international law. One of those important duties is to prevent its territory from being used as a base for attacks on its neighbors. If anything, ISIS exists to spread a fundamentalist Islamic revolution that calls for the replacement of existing Arab regimes with a universal caliphate. It uses its territory as a training camp and staging ground for fighters who will remain in the region or travel to western nations to launch terrorist attacks covertly.

Terrorism places further demands on self-defense. Terrorist groups do not deploy large military forces. American intelligence cannot effectively use satellite reconnaissance to detect the deployment of terrorist units days or weeks in advance. Terrorists do not launch cross-border attacks with regular armed units to seize territory, rather, they seek to covertly infiltrate a country by blending into domestic society. Their goal is to launch surprise attacks primarily on civilian targets. A temporal imminence test loses its value if a nation cannot detect the enemy’s preparations in anticipation for war. By the time the nation detects an attack, it may well be too late because the attack will already have occurred. As WMD technology becomes cheaper and more available, the difficulties posed by terrorism will only increase. Groups such as al-Qaeda, Hezbollah, and Hamas have the financial resources to acquire chemical, biological, and perhaps even nuclear weapons capable of killing tens of thousands of civilians indiscriminately. Imminence as a limiting rule on the use of force suffers because non-state enemies can launch attacks with greater speed, surprise, and destructiveness than ever before.

In order to fight terrorism effectively, nations will have to use force well before an attack becomes imminent. They will have to act when a terrorist leader or a collection of fighters becomes known to intelligence agencies, even though they may be weeks or months away from executing a possible plot. At the same time, because the odds of an attack are lower, it would be reasonable to resort only to less harmful methods of coercion. If a terrorist attack were imminent, a government could destroy camps, buildings, and units using less precise conventional artillery or missiles with high-yield warheads. But if an attack is less certain, it would be more justifiable to deploy precision-guided munitions against selected leadership or logistics targets that will cause less collateral harm. As the certainty of an attack falls, its expected harm falls too; nations should adjust their measures accordingly. A nation under threat of terrorist attack may resort to force more often, because it is heading off multiple plots long before they mature, but it will also employ more precise weapons that keep harm to the necessary minimum.

Maintaining International Order

The most important use of new weapons may involve preventing states from threatening their neighbors. Even as the Cold War’s end reduced the threat of nuclear armageddon, it opened a Pandora’s box of new threats to the peace by regional rivalries. Western nations have failed to contain these efforts to rewrite the international order because of the incremental, low-level nature of the hostilities conducted by regional powers. New technologies might provide a means to carefully calibrate a forceful response, beyond mere diplomatic protest, that could counter efforts to upset the U.S.-led liberal international order.

Russia has probably become the number one revanchist power in the world. Seeking to restore its influence in its “near abroad,” Russia invaded Georgia in 2008 and annexed the Crimean peninsula in 2014—the first change in European borders by force since 1945. It has engaged in a covert military intervention and provocations to foment unrest in the rest of Ukraine. It has intervened in the Syrian civil war with bombers, cruise missiles, and small ground units, and has sparked tensions with Turkey while cooperating with Iran. It has launched a military buildup (increasing military spending by 7.5 percent to $66.4 billion in 2015),⁴⁷ despite its declining economy, and has adopted a muscular deployment of forces along its borders with E.U. states.

China’s stunning economic rise has sparked a parallel increase in its military and diplomatic place in the world.⁴⁸ While China currently cannot challenge American superiority in the global commons of the air and sea, the trajectory of its economic and military growth foreshadows a day when it will be able to deny the U.S. access to the seas around East Asia and contest it for supremacy in the Pacific Ocean. China now boasts the second largest military budget in the world, at $215 billion per year, an increase of 132 percent in the last 10 years.⁴⁹ It has embarked on a military buildup that extends beyond territorial defense to power projection abroad. China has given strong signs of what it will do with new ballistic missiles and a sophisticated navy in its seizure of disputed islands in the midst of the South China Sea, declaration of air defense zones over the Senkaku island chain off of Japan, and its threats against Taiwan. Communist China does not naturally seek peace; since taking power in 1950, its leadership has launched wars against many of its neighbors, seized control in Tibet, and fought the United States over Korea.

Although one is declining while the other is rising, both Russia and China seek to revise the American-sponsored balance of power in their regions. To be sure, the United States remains the world’s hegemonic power, one whose dominance in economic and military strength may be unprecedented in modern history. It deploys expeditionary forces from a network of bases around the world, it maintains a liberal trading and political system, and it keeps open the air and seas. Even though U.S. military expenditures fell during the Obama years, the $596 billion American defense budget dwarfs that of the other great powers and represents more than one-third of all global military spending.⁵⁰ These figures understate American control of the global commons—air, sea, space, and now cyber—necessary for the projection of power worldwide, and its ability to leverage its economic and technological advances into military ones.⁵¹

Nonetheless, the United States must stretch its forces globally to maintain order, while Russia or China need only achieve regional superiority. Large mechanized armies bent on territorial conquest may have become less relevant. The war to reverse Iraq’s 1990 invasion of Kuwait may be the last such war we will see for some time. But that does not mean that regional powers will foreswear the use of force against the United States and its allies. Instead, they will exploit means of coercion that fall short of the level necessary to spark any serious conventional armed response. China, for example, has pressed its dubious maritime claims in the South China Sea by converting small shoals and rocks near the Philippines into bases.⁵² Russia pressures Ukraine by sending weapons, air and artillery support, and even irregular troops to prop up a supposed independence movement along its border.⁵³ Both nations are conducting a low-intensity struggle with the United States in cyberspace, with China stealing the U.S. government personnel database in 2015 and Russia hacking into the electronic files of the Democratic National Committee and Clinton campaign leaders in 2016. Even if nuclear weapons and American hegemony render direct conventional war less likely, nations will still pursue their interests by coercing other states.

Rogue states, as the Clinton and Bush administrations called them, or “states of concern” in the Obama years, compound these threats to international peace and stability. Whatever their name, these autocratic states both oppress their own populations and threaten their neighbors. North Korea, for example, remains one of the most extreme dictatorships on earth, with a population deprived of basic services and subject to famine and starvation, an oppressive police state, with one of the world’s smallest per capita GNP. At the same time, the Kim regime devotes the lion’s share of its budget to its armed forces. North Korea maintains the fifth largest army in the world and it periodically launches attacks on South Korea, such as the 2010 sinking of a South Korean warship.

Iran has joined North Korea in challenging the regional status quo with a level of hostilities that fall short of outright war. Iran supports religious militias such as Hezbollah, which harasses Israel from southern Lebanon, and sends irregular troops to support the Assad regime in the Syrian civil war. It supported Shiite militia groups during the Iraq war. Both Iran and North Korea bolster their revisionist agendas with programs to develop nuclear weapons and ballistic missiles, which would allow them to pursue their unconventional attacks without fear of reprisal. Their programs could spark a nuclear arms race in the Middle East, where Saudi Arabia and Egypt might seek to match Iran, or in East Asia, where Japan and South Korea might develop nuclear deterrents. Rogue nations refuse to abide by the basic principles of the international system and may seek to export revolution or disrupt the existing order. Yet, their autocratic natures and revolutionary worldviews make them less susceptible to diplomatic or political pressure.

Some nations may bear ill will toward the United States, such as Venezuela, but have few military means to inflict harm. Only very limited American force could be justified to forestall a threat from Caracas. Other nations, however, such as North Korea, present themselves as rivals and are acquiring the means to attack. Pyongyang still considers itself at war with the U.S. and South Korea and holds the national goal of expelling American troops and forcibly unifying the peninsula under its regime. While the Kim regime has held the capacity to attack American troops stationed in South Korea since 1953, it posed no military threat to the continental United States. In 2016, however, North Korea successfully tested a 10-kiloton nuclear weapon, and in 2012 it launched a satellite into low-Earth orbit—the technology necessary to develop a ballistic missile capable of striking North America.⁵⁴ As the magnitude of the harm posed by Pyongyang has increased dramatically (nuclear weapons), and the likelihood it could execute an attack is rising sharply (ballistic missiles), the United States could legitimately employ more destructive means to squelch the threat of a North Korean attack. More precise weapons may give the United States the means to degrade or eliminate a North Korean nuclear threat without causing the wider harm that might trigger a broader war.

The pace of today’s most pressing international threats seems to be set by the disintegration of states and the rise of civil wars, the spread of terrorism, and the proliferation of WMD technology, as well as their negative spillover effects upon neighbors, or the international system as a whole. To be sure, the threat of conventional conflicts between states always exists, though the odds of a war between the great powers has receded since the end of World War II. While the chances of great power conflict have decreased, the capability to duplicate their destructiveness has expanded because of the spread of technology into less responsible hands. But technology may also present the means to curb these threats. New weapons technologies may provide western states with the ability to use more precise, focused force to punish oppressive regimes intent on genocide. They can allow nations to pursue terrorists into lands inaccessible by ground or sea units. They can raise the costs on rogue states seeking WMD or rising powers seeking to upend regional stability. To fully understand the reasons why new technology may succeed, we will now examine a useful theory to explain why force may help in keeping the peace.

Using Force to Commit to Peace

In order to control these threats, nations must return to the use of force as a means of coercion. Great powers have long used force to pressure each other. Even in the twenty-first century, nations will continue to advance their interests, at times with conflict, and at other times with cooperation. New military technologies will make it feasible for nations to use force more often, rather than less, because they will be able to achieve their aims without triggering broader war. In this section, we turn our attention to one possible theory that could help explain why expanding the methods of force could encourage greater peace between the great powers.

We do not adopt this approach as the sole foundation for our account of war, technology, and law, rather, we develop it as a possible theory that supports our intuition that advancing weapons technology can lead to less conflict. This theory sees war as the failure of rational nations to reach a settlement of their disputes. The anarchy of the international system undermines the bargaining process because nations have uncertain information about their opponents’ capabilities and cannot trust them to keep their promises. More ways to use force could provide leaders with greater means of signaling their seriousness of will, military capabilities, and commitment to avoid war. That may justify the counterintuitive conclusion that new technology can bring more, rather than less, peace.

Our world might be safer if it were more actively policed, just as more active policing has reduced violent crime in American cities.⁵⁵ The international system, however, lacks an effective supranational government that can stop violence in the same way that domestic institutions maintain law and order at home. Not only must nations use force more broadly in self-defense, but in the absence of an effective government they must also intervene to prevent threats to global welfare from weapons of mass destruction, terrorism, and aggressive authoritarian nations. Rivals such as Russia and China pose a tough challenge for this mission. Both nations enjoy the resources and militaries to place them in the rank of great powers. Their ambitions clash with U.S. interests, from Eastern Europe to the seas of the western Pacific. While their intentions may make them rivals of the United States, however, their own economic status gives them a great deal to lose. American power likely deters them from any direct, widespread conflict.

Critics, on the other hand, believe that new weapons could make the use of force cheaper, and hence war more commonplace. But we believe this view is mistaken. The ability to use force more precisely will prove a benefit to the international system. The signaling of resolve and capability through less destructive attacks can help avoid the worldwide conflicts that caused such grave human suffering and death in the twentieth century. Ironically, the availability of new weapons technologies should reduce the chances of great power war and lead to more settlement of conflicts.

If there is a place for coercion (as opposed to merely repelling attacks), however, the scope for resort to force must be enlarged. It will no longer be obvious that retaliatory measures must actually be limited to attacks on “military objectives.”⁵⁶ Keeping the peace today requires a return to earlier understandings of the use of force. International law should allow nations to use force against civilian targets, so long as they do not involve lethal means of coercion. Recent efforts to apply a broad definition of the principle of distinction to twenty-first century conflicts should be relaxed, because they will have the unintended and perverse consequence of rendering war more likely and more destructive.

Even if our approach were to allow the great powers to suppress WMD proliferation, humanitarian crises, and terrorism, critics will worry that it will encourage conflict. Wider discretion in the use of force will result in more violence, which could increase the risks of war. Close attention to a promising theory of international crises, however, suggests that new weapons may actually reduce, rather than increase, the chances of war. Great powers will go to war when they fail to reach a negotiated settlement of their differences. They can bargain with each other using diplomacy, but when words alone fail, they must resort to demonstrations or even applications of force. New weapons provide states with the means to exert pressure at lower levels of destruction and casualties, which provides great powers in a crisis more opportunities to divert from escalation to settlement.

Rivalries will still endure and nations will still have disputes. But a promising theory of conflict suggests that rational nations should settle their disputes when the gains from cooperation outweigh the benefits of conflict. As Thomas Schelling argued, “Conflict situations are essentially bargaining situations.”⁵⁷ Situations involving the possibility of armed conflict produce high incentives to avoid the losses from going to war.⁵⁸ Nations can settle their disputes in a way that gives each side some benefit while foregoing the loss of life and resources due to armed conflict. This approach bears similarities to a law and economics analysis of litigation, where parties acting rationally and with full information should always prefer settlement to the great expense of going to court.⁵⁹ Similarly, nations that have full information about military resources and political will should prefer an agreement instead of a conflict that wastes resources and will probably produce the same outcome.

International agreements serve as a means to resolve disputes between nations. Treaties can resolve border disputes, formalize the transfer of territory, or promise favored treatment for citizens and goods and services. Peace treaties recognize the end of a war. Nations, however, encounter significant obstacles to the enforcement of treaties. At home, parties can rely on a legal system, backed up by courts and police, to enforce a settlement. International anarchy, however, interferes with the ability of states to enforce agreements, despite their obvious benefits to both parties. Without international courts or police with effective authority to elicit compliance, a nation-state can renege on a treaty without consequence other than retaliation from other states.

This produces a classic prisoner’s dilemma.⁶⁰ Nations might not enter into treaties because they do not trust their partners. This problem will be particularly acute where one party must take a first step that bears high costs before the other party must act. For example, a nation that has strong offensive military capabilities, but weak defensive systems, may be reluctant to refrain from positioning troops in a disputed territory and lose its tactical advantages without a firm guarantee that the other side will do the same. Without institutional mechanisms for enforcement, the first nation cannot be sure that the second nation will not exploit its own commitment to demilitarize in order to seize the disputed territory.

Nations should agree to a deal which reflects their chances of prevailing in a conflict, which depends on the balance of forces between the two sides. Each nation will have an expected value that it places on winning a dispute. The expected value of a war equals its expected benefit minus its expected cost. The expected benefit will be a nation’s probability of prevailing times the value of winning. The expected costs of the conflict will be the likely losses suffered from fighting. Before they launch a conflict, governments must estimate the probability of winning, the likely benefits from victory, and the costs of securing it. If both sides could know these things in advance, they should compromise accordingly. If one state is likely to win important benefits at a small cost, the potential opponent may see resistance as futile. If the attacker sees that conflict would entail large costs for no substantial gain, it does better by withdrawing or reducing its claims. In either case, war would be irrational.

Successful bargaining requires that nations act rationally. Leaders, however, may be delusional or motivated by incentives other than costs and benefits, such as a messianic religious vision. There will be less room to compromise with these regimes. They may hold little concern about the welfare of their people while giving much more attention to preserving their own hold on power. Such nations might still risk going to war, even though they have a low probability of winning and a high cost of casualties, because the odds are higher that the regime will remain in power. Compromise with authoritarian regimes will prove difficult, as with Saddam Hussein’s Iraq during the first and second Persian Gulf Wars. Nations may also place such different values on the matter in dispute that there is no real overlap in the range of outcomes they will accept. If Beijing, for example, values Taiwan far more highly than Washington because of the symbolic and historical meaning of uniting China, the expected values of the two countries might not make a settlement possible.

Lack of a supranational government makes agreement even more difficult because nations cannot trust the information that they receive. If nations do not know important variables, such as the probabilities of winning a conflict, the value that their rivals place on a contested resource, or expected war costs, they will be unable to decide accurately whether to go to war or to settle. The most important factor in this calculus is a nation’s probability of winning a conflict, which depends on military capabilities and political determination. Information in the public domain, such as military size, defense budgets, and economic growth, can provide some clues about a nation’s military strength. But even these relevant public facts may prove difficult to collect and analyze. During the 1970s and 1980s, for example, the CIA badly mistook the size of the Soviet defense budget and underestimated Moscow’s large amount of spending necessary to keep up with the U.S. The Soviet Union’s quick collapse in 1989-90, therefore, came as a surprise to most of the American national security establishment.⁶¹ Even if accurate figures are publicly available, economic growth may not directly translate into military effectiveness because of weakness in military equipment, training, or culture.

Other relevant information will fall primarily within the control of the opponent. The United States, for example, will have private information on the quality of its armed forces and the superiority of its strategies and tactics. Indeed, nations will go to great lengths to conceal military abilities in order to preserve tactical advantages or strategic surprise. The United States keeps performance data on many of its weapons systems classified, which makes it more difficult for the enemy to develop effective countermeasures. Imperial Japan concealed its advances in aircraft carrier operations, which allowed it to project force as far as Hawaii, well beyond American estimates at the time. Nations will also have private information on the political willingness of their leadership, elites, and people to fight. One nation may be willing to suffer vastly higher casualties than the other, which affects their probability of winning a conflict. While the United States suffered about 58,000 deaths in the Vietnam War, North Vietnam and the Viet Cong bore losses estimated at least ten times that number.⁶²

Lack of knowledge of an opponent’s military capabilities and political resolve creates an information asymmetry. Information asymmetries inhibit the reaching of agreements, whether they are domestic contracts or the settlement of international disputes. First, imperfect information will lead to mistakes in bargaining. If nations overestimate their probability of winning a conflict, and correspondingly underestimate their opponent’s odds, they will not realize there is a broader range for agreement. This lack of information will result in less settlement and more war. Second, nations will also have an incentive to bluff. A nation might seek to hide its military abilities in order to gain a tactical or strategic advantage. Or a nation will exaggerate its resources in order to bluff its way to a better deal. Great Britain and France mistook Germany’s capabilities in 1938 and 1939, which allowed Berlin to seize Czechoslovakia and invade Poland without response. Faced with possible bluffs, nations will have few means of gaining credible information about their opponents’ true capabilities. Such uncertainty will undermine the ability to reach a deal.

Third, nations will have few ways to credibly reveal private information. In order to avoid the costs of war, a nation may wish to communicate information on its true capabilities to its opponent. This picture will allow parties to reach a more accurate prediction of a dispute’s outcome, which should smooth the way to a settlement. In domestic litigation, for example, the parties to a lawsuit can reveal information through discovery in federal court that provides credibility. But under conditions of anarchy, nations will have difficulty revealing private information in a credible manner.

More precise, less destructive uses of force can help overcome the obstacles of imperfect information. Coercive measures can signal political will, the value placed on the resources at stake, or military capabilities that could influence the outcome of a broader armed conflict. The more costly the signal, the more credible the information becomes. A nation’s leader can make a threat of war and send military forces near disputed territory or a potential conflict zone. Deployment eats up resources that would go to waste if the nation is bluffing. It also incurs “audience costs” domestically, because a leader will suffer politically if he aggressively deploys force but then backs down.⁶³ Escalating steps of force will provide the opportunity to send more precise signals that gradually consume more resources, reveal more military capability, and edge closer to war. More signaling should reduce the chances of bluffing and reveal more reliable private information.

A good example is the Cuban Missile Crisis. The U.S.S.R. sought a rapid change to the balance of power in its favor by stationing intermediate-range nuclear missiles in Cuba. At this time, the United States had an ample deterrent capable of striking Soviet territory, while Russian forces could not yet match U.S. levels—this would change after the crisis when Moscow embarked on a program to build a large arsenal of ICBMs. President Kennedy decided to prevent the deployment. But before launching an all-out attack on the missiles, the United States effectively sought to force Soviet premier Nikita Khrushchev to agree to cancel the move. Kennedy ordered a limited use of force, a naval blockade of Cuba, which sent a signal of his willingness to use force to remove the missiles, and the U.S.’s military capabilities. He reinforced these messages by placing U.S. nuclear forces on high alert. But using limited coercive means allowed Washington to reach a negotiated settlement with Moscow that avoided the costs of a direct conventional conflict.

As Schelling suggested, the Korean War may provide another example. The United States directly fought against North Korea, which was supported initially by the Soviet Union. After Chinese intervention in December 1950, the United States conducted hostilities directly against another great power. The conflict, however, remained limited both in geography and means. Hostilities never left the Korean peninsula, despite the proximity of U.S. forces in Japan and Chinese bases in Manchuria. Both sides only resorted to conventional weapons, despite a large advantage in U.S. nuclear weapons and delivery systems. After Chinese intervention, both nations engaged in grueling ground combat for two years, even though the front settled early around the original dividing line between North and South Korea. Acceptance of high casualties by both the U.S. and China signaled their unwillingness to accept a peace that deviated from the original 38th parallel. It also demonstrated their credibility in respecting an armistice or cease-fire, because the alternative would be a renewal of costly fighting for little benefit.

If nations engage in such signaling as part of the bargaining over a settlement of their disputes, means of exerting limited force will prove valuable as ways to demonstrate resolve without choosing between complete acquiescence to enemy demands or all-out war. Instead of a naval embargo, or costly ground tactics, the United States could bargain with Russia or China with new types of weapons, such as drones or cyber. New technologies might not prevent a conflict from breaking out, but they will provide more opportunities to reach a negotiated settlement to avoid full great power hostilities. Conversely, limiting the ability to use lower levels of force might have the unintended consequence of rendering war more harmful. A ban on new weapons, for example, could narrow the range of targets and the means of coercion to produce more destructive signaling and ultimately more lethal conflicts. One nation may want to send a signal during a crisis that inflicts a precise cost on its opponent. With a broader set of targets and more levels of harm, the nations can send more discrete signals. But if nations limit their signals to kinetic attacks on military targets, they will have to employ more destructive levels of force. They might develop even more devastating kinetic weapons to produce the same effects as the precision offered by cyber or robotic weapons. Limits on new weapons technology might even destabilize crises by encouraging nations to use offensive weapons early in a crisis which might themselves be vulnerable to attack.⁶⁴

Take, for example, disabling an opponent’s financial markets or transportation and communications networks. During the Kosovo War, the United States Air Force dropped graphite on Belgrade’s electrical grid, which temporarily disabled power to Serbia’s capital city. While NATO claimed that the disruption in electricity undermined Serbian military operations, the attack on the electricity grid also sought to pressure Serbian civilians against supporting the Milosevic regime.⁶⁵ While such an attack would violate the ban on targeting civilian objects set out in the Additional Protocol I of 1977 to the Geneva Conventions, it could send a signal that might yield less loss of life and destruction than an attack on a hardened military target using kinetic weapons.

New technologies present opportunities, and dangers too, to send a greater diversity and range of signals during interstate crises. Nations could use cyber attacks to target each other’s armed forces more precisely, and hence reduce direct casualties to both military personnel and civilians. While sending that message would inflict harm, it could avoid the casualties and physical destruction of a kinetic attack. Cyber attacks might reduce the collateral harm to civilians by disrupting only military communications networks or stealing only classified intelligence. While cyber attacks certainly could cause widespread harm, such as cutting water and electricity services to civilian populations, they could also simply disrupt a government’s command-and-control of its military assets. Even if deployed against civilian targets, cyber weapons could still offer more precise and controlled power than a kinetic weapon.

The anarchy of the international system creates a second obstacle to cooperation. Even with perfect information, nations may still refuse to reach a peaceful settlement because they lack confidence that their opponent will keep its promises. They may understand that they will both be better off by avoiding war, for example, but nations may not trust each other to obey the agreement in the future. This problem will prove particularly acute in situations where a settlement changes the status quo between states or where rapid changes are affecting the balance of power.⁶⁶ One nation will find it difficult to trust its opponent to keep a promise if the latter will become even more powerful as a result of the agreement. New weapons technologies might provide new ways to increase commitment to an agreement. It provides states with more measured ways to sanction nations to stop violations, short of terminating an agreement altogether. Precision cyber and drone attacks provide more steps of coercion beyond diplomacy and economic pressure but are short of conventional armed conflict.

A critic might argue that without international regulation of these new technologies, the risk to civilians will increase. Nations at war, however, will have an incentive to distinguish between military and civilian targets to the extent allowed by the capabilities of weapon systems. Rational nations should seek to contain the harms of war in order to maintain the conditions for peace and to preserve the value of the civilian economy in the postwar period.⁶⁷ Defenders in a war do not want to kill their fellow citizens or harm their own territory, although they might destroy civilian property to prevent it from falling into the hands of the enemy. Conversely, invaders will have no interest in ruining the object of their aggression. Reducing civilian casualties may also encourage an end to conflict. Targeting civilians and destroying non-military resources may harden nations at war and make a diplomatic compromise more difficult. The unexpected carnage of World War I, for example, made peace restoring the status quo ante politically impossible for both the Allied and Central Powers.

Nations have long pursued indirect coercion against civilian populations in war. As we will describe more fully in the next chapter, they have often turned to economic sanctions to conduct hostilities short of armed conflict, or in conjunction with active hostilities. These sanctions pursued the objective of weakening the support of the civilian population for a regime’s military policies. In World Wars I and II, the Allies conducted economic warfare against Germany and its allies by levying a blockade of civilian shipping.⁶⁸ After the wars, the U.N. Charter even expressed a preference for such tactics by authorizing the Security Council to impose “complete or partial interruption of economic relations and of rail, sea, air, postal, telegraphic, radio, and other means of communication” in the case of a threat to international peace and security.⁶⁹

Economic warfare serves the same objectives as the approach described here for cyber and robotic weapons. First, it provides nations with a way to send signals in international bargaining through the gradual escalation of coercion, just as western nations used sanctions to bring Iran to the negotiating table over its nuclear program. Second, embargoes pressure civilian populations to change the policies of their leaders, or even the leaders themselves. While nations such as Great Britain and the U.S. have argued that embargoes only blocked goods that might contribute to an enemy war effort, the complete embargoes that prevailed during the World Wars seemed equally, if not more, directed against civilians. Perhaps new technologies, when employed as steps in the escalation of force, will also be understood as more akin to economic warfare than conventional bombing.

Limiting the use of force in a war bargaining situation can have several harmful effects. First, narrowing the range of targets only to military objects could have the effect of escalating the damage of signaling. In a crisis, nation A may want to send a signal that inflicts a certain cost on nation B. With a broader base of civilian targets, nation A could choose a relatively low level of harm to produce the desired level of coercion. Temporarily knocking out the electricity supply to the capital city, for example, will cause inconvenience to a large number of civilians. To produce the same level of harm upon a smaller base of military personnel and assets will require a higher level of force. Attempting to coerce nation B—consistent with a broad approach to distinction—might require nation A to attack and potentially destroy nation B’s military targets and kill military personnel. Limiting the universe of targets to purely military sites could even provoke extreme crises by encouraging nations to launch vulnerable offensive weapons first, before they themselves are attacked. This “use it or lose it” incentive could force early and extreme escalations of a crisis into a military conflict.⁷⁰

A prohibition on certain targets could also raise the chances of miscommunications that might have the unintended consequence of leading to war. Barring attacks on civilian assets will reduce the number of possible targets; only military personnel, facilities, and assets would be fair game. This strategy will limit the means of coercion between states. Only military means will prove effective against military units. It may also prove impossible, even with highly precise guided munitions, to tailor non-lethal uses of force solely to strike military units. Disrupting electrical supplies or destroying fuel stocks may exert low-intensity coercion against an opposing military, but it may also hurt civilians and non-military installations equally, if not worse. Other types of non-lethal tactics, such as cutting off access to the international financial system, may not have any direct effect on military targets at all.

Limiting force only to military targets may encourage the development and use of more destructive munitions. If nations expect that coercion will only take the form of attacks on their militaries, they will make military targets more difficult to attack. They may improve their military defenses to the extent that the attacking nation must deploy a significantly greater level of force to prevail. A defending nation, for example, might place critical facilities underground or in bunkers. It might even disperse critical military assets among the civilian population. Attacking military targets may force a nation to undertake an act of greater force to seek resolution of a dispute, while using lower levels of non-lethal force involving civilian targets might have equally communicated its message.

Reducing the number and types of targets and limiting the means to pursue them would increase the odds of war. Imperfect information can lead rational states to miscalculate. If there are further steps to convey reliable information, nations will have more accurate information on the expected values of war. That information will allow them to consider settlements before making the fateful decision for war. The more steps up an escalatory ladder, the more opportunity nations have to jump off before they reach the stage of armed conflict. On the other hand, limiting the ability of nations to communicate will reduce their ability to reach settlements of their differences. If nations have less opportunity to credibly signal information to each other, the chances of miscalculation and war will increase.

The twenty-first century has brought new types of security challenges to the United States and its allies. Where the last century saw worldwide war between continent-spanning alliances, today the threats to peace come from regional powers, rogue nations, terrorist groups, and civil wars. The West should maintain international peace and stability by employing the full spectrum of force made available by technological progress. It should also use force to prevent looming threats posed by terrorism or the internal breakdown of states from maturing into catastrophes. Contrary to the concerns of some, broadening the use of force will not lead to more war. It should allow the international system to reduce the number of more harmful conflicts by allowing nations to communicate their intentions more clearly, which should produce more settlement of disputes without resorting to war.

The U.N. Charter Rules

As Syria shows, the world is returning to the idea that the international system allows punitive measures. This runs counter to the view, embraced by most specialists in international law, that the U.N. Charter banished the idea of punishing states for misconduct. In 2013, for example, Gabriella Blum concluded that “the moral rhetoric of state ‘crime and punishment’ has been excised from the lexicon of international law” so that “coercive action against states can no longer be justified by any punitive urge but instead must be couched in terms of regulatory or preventive action.”⁷¹ Blum questioned the value of this shift, even as a means of reducing resort to force in international affairs. But she still saw the renunciation of punishment as the culmination of long-developing trends, already visible before the establishment of the United Nations.