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
Actions of 30 September – 4 October 1917 the counter-attack. After the attack of 26 September, the British had used information from prisoners, gleanings from the battlefield and ground observation to judge the state of the 4th Army. The concentration of the German heavy artillery into the Tenbrielen, Kruiseecke, Becelaere and Keiberg groups directed towards Menin Road Ridge, Tower Hamlets Ridge, Polygon Wood and Broodseinde Ridge was reported on 29 September by I Anzac Corps flash spotters; RFC reconnaissance flights confirmed the changes but this took from 1 to 2 October, because Germans hid the redeployment with smoke screens. By 29 September, the 4th Army had recovered from