Chemical weapons in World War I in Palestine during the Second Battle of Gaza. Russia began manufacturing chlorine gas in 1916, with phosgene being produced later in the year. Most of the manufactured gas was never used. The British Army first used mustard gas in November 1917 at Cambrai, after their 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 1918 during the breaking
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