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
Action of 25 September 1917 the night. An intelligence summary of the Second Army assessed the German artillery in support of the of 25 September, to have been the greatest concentration of artillery on a German divisional sector ever known and was nearly four times the usual quantity for a division. The attacking battalions had assembled during the night of covered by parties of the line-holding battalions opposite the 33rd Division. The great mass of German artillery began a bombardment at but fell short and German infantry fired red flares to signal to the German artillery that they were falling short, especially on the III