| 28 June | Archduke Franz Ferdinand assassinated in Sarajevo |
| 23 July | Austria-Hungary’s ultimatum delivered to Serbia |
| 28 July | Austria-Hungary declares war on Serbia |
| 29 July | Austrians bombard Belgrade |
| 31 July | Russia mobilises,fn1 German ultimatums dispatched to Paris and St Petersburg |
| 1 August | Germany and France mobilise |
| 3 August | Germany declares war on France |
| 4 August | Germany invades Belgium, Britain declares war on Germany |
| 8 August | French briefly occupy Mulhouse in Alsace |
| 13 August | Austrians invade Serbia, French launch major thrusts into Alsace and Lorraine |
| 15 August | First Russo-Austrian clashes in Galicia |
| 16 August | Last fort of Liège falls to the Germans |
| 20 August | Serbs inflict defeat on Austrians at Mount Cer |
| 20 August | Brussels falls |
| 20 August | French repulsed at Morhange |
| 20 August | Germans defeated at Gumbinnen in East Prussia |
| 22 August | France loses 27,000 men killed in one day of the abortive ‘Battles of the Frontiers’ |
| 21–23 August | Battle of Charleroi |
| 23 August | British Expeditionary Force fights first action at Mons |
| 24–29 August | Battle of Tannenberg |
| 26 August | BEF fights at Le Cateau |
| 28 August | Battle of Heligoland Bight |
| 29 August | Battle of Guise |
| 2 September | Austrian fortress of Lemberg falls to the Russians |
| 6 September | France launches Marne counter-offensive |
| 7 September | Austrians renew invasion of Serbia |
| 9 September | Germans begin retreat to the Aisne |
| 9 September | Battle of the Masurian Lakes |
| 23 September | Japan declares war on Germany |
| 9 October | Antwerp falls |
| 10 October | Austrian fortress of Przemyśl falls to the Russians |
| 12 October | Flanders campaign begins, climaxing in three-week First Battle of Ypres |
| 29 October | Ottoman Empire enters the war on the side of the Central Powers |
| 18–24 November | Battle of Łódź, ending in German withdrawal |
| 2 December | Belgrade falls |
| 15 December | Austrian army in Galicia driven back to the Carpathians |
| 17 December | Austrians once more expelled from Serbia |
