Ypres east of the town. The first gas attack occurred against Canadian, British, and French soldiers, including both metropolitan French soldiers as well as Senegalese and Algerian tirailleurs (light infantry) from French Africa. The gas used was chlorine. Mustard gas, also called Yperite from the name of this town, was also used for the first time near Ypres, in the autumn of 1917. Of the battles, the largest, best-known, and most costly in human suffering was the Third Battle of Ypres (31 July to 6 November 1917, also known as the Battle of Passchendaele), in which the British, Canadian, ANZAC, and
Action of 25 September 1917 defeat German counter-attacks, by advancing no more than and then consolidating their positions, preferably on reverse-slopes. When the Germans counter-attacked, they would encounter a British defence-in-depth protected by artillery and suffer many casualties to little effect, rather than the small and disorganised groups of infantry that the Germans had driven back on 31 July, After the big defeat at the Battle of the Menin Road Ridge on 20 September, the 4th Army changed the organisation of regiments and battalions in their defensive positions. During August, each German front-line division had kept two regiments in the front position, with all six