Sulfur mustard later also against the French Second Army. The name Yperite comes from its usage by the German army near the town of Ypres. The Allies did not use mustard agent until November 1917 at Cambrai, France, after the armies had captured a stockpile of German mustard shells. It took the British more than a year to develop their own mustard agent 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 of the Hindenburg Line. Mustard agent was dispersed
Action of 25 September 1917 September, German troops were to conduct a on the Fifth Army front opposite the 20th (Light) Division in XIV Corps and a bigger attack against the X Corps front, in the centre of the Second Army, south of the I Anzac Corps in Polygon Wood. The 50th Reserve Division had been the "Eingreif" division for from and was moved south to the Menin area as a reserve. The division relieved the Bavarian "Ersatz" Division on 21 September, Reserve Infantry Regiment 231 (RIR 231) south of the Menin road, RIR 230 north of the road to the Reutelbeek and RIR 229