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
German Type U 151 submarine U 139 "U-cruisers", designed from the outset as military submarines. "Deutschland" made two successful commercial voyages before being commissioned into the Kaiserliche Marine on February 17, 1917 as "U-155". Max Valentiner commanded a Type U 151 U-boat, , and undertook the longest cruise in the war from 27 November 1917 to 15 April 1918, a total of 139 days. High-scoring Waldemar Kophamel also commanded a Type U 151 U-boat, in late summer and fall of 1917. Seven Type U 151 submarines were built, of which six were commissioned into the Kaiserliche Marine. German Type U 151 submarine Type U 151