Chemical weapons and the United Kingdom army against British and Canadian soldiers near Ypres, Belgium, in 1917 and later also against the French Second Army. The name Yprite comes from its usage by the German army near the town of Ypres. The Allies did not use mustard gas until November 1917 at Cambrai, France, after the armies had captured a stockpile of German mustard-gas shells. It took the British more than a year to develop their own mustard gas weapon, with production of the chemicals centred on Avonmouth Docks. (The only option available to the British was the Despretz–Niemann–Guthrie process). This was used first in September
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