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 increase the accuracy of German artillery-fire as the British attacked. On 23 September, Crown Prince Rupprecht wrote in his diary that the higher ground at Zonnebeke and Gheluvelt was vulnerable to another British attack and that it was vital that the German counter-attack tactic did not fail again. Next day, Rupprecht wrote that he hoped that another British attack would be delayed, as the 4th Army had insufficient reserves for the whole of the active front east of Ypres. Rupprecht ordered a (methodical counter-attack) against the British flank between the Menin Road and Polygon Wood, which was longer after the