Chemical weapons in World War I volatile oily liquid. It was introduced as a vesicant by Germany in July 1917 prior to the Third Battle of Ypres. The Germans marked their shells yellow for mustard gas and green for chlorine and phosgene; hence they called the new gas "Yellow Cross". It was known to the British as "HS" ("Hun Stuff"), and the French called it "Yperite" (named after Ypres). Mustard gas is not an effective killing agent (though in high enough doses it is fatal) but can be used to harass and disable the enemy and pollute the battlefield. Delivered in artillery shells, mustard gas was
British home army in the First World War as still essentially a body of amateurs and echoed the War Office's earlier call for a smaller, better trained auxiliary. At the end of 1917, the huge losses suffered by the BEF during the Third Battle of Ypres, the implications of the October Revolution in Russia, the Austro-German success in the Battle of Caporetto on the Italian Front and the anticipated German Spring Offensive generated a surge in demand for manpower. In December, the army was prioritised below the navy, the Royal Flying Corps, the shipbuilding, aircraft and tank manufacturing industries, and food and timber production for the allocation of