- Lieutenant-General Sir Archibald Murray is appointed Chief of the Imperial General Staff, Great Britain
- British forces defeat the Turks at the Battle of Kut al-Amara in Mesopotamia. The resounding victory spurs an ambitious move by the British to venture onward to quickly capture Baghdad. However, that attempt fails and the troops return to Kut-al-Amara.
- The French launch their third attempt to seize Vimy Ridge from the Germans in Artois; they succeed
- The invasion of Serbia begins as Austro-German troops attack from the north. Five days later, the Bulgarians attack from the east. The outnumbered Serbs have their poorly supplied troops stretched too thinly to defend both fronts. Belgrade then falls to the Germans and the Bulgarians capture Kumanova, severing the country’s north-south rail line. This leaves the overwhelmed Serbian troops no option other than to retreat westward through the mountains into Albania.