A British 18-pounder field gun battery taking up new positions close to a communication trench near Boesinghe on the opening day Third Battle of Ypres, 31 July 1917, Lieutenant John Warwick Brooke. Image courtesy Imperial War Museum © IWM (Q 5723).
- British and French troops launch a new offensive on the Western Front, attacking along a 24km front in Flanders, Belgium, taking 12 villages and capturing 5,000 prisoners. The attack begins more than three months of brutal fighting, known as the Third Battle of Ypres or the Battle of Passchendaele. Fighting would continue until 10 November, when Commander in Chief of the British Expeditionary Force in France and Belgium, Sir Douglas Haig called off the offensive, claiming victory, despite some 310,000 British casualties, as opposed to 260,000 on the German side. The major actions involving Australians were at Menin Road, Polygon Wood, Broodseinde, Poelcappelle, and Passchendaele.
- German and Austro-Hungarian forces on the Eastern Front continue their advance in Galician front, crossing the west bank of the Zbrucz River
