British war crimes September 1915 and continued their usage for the remainder of the war. This was done in retaliation for the use of chlorine by Imperial German Army the preceding April. Following the Imperial German Army's use of poison gas at Ypres, the commander of II Corps, Lieutenant General Sir Charles Ferguson, had said of poison gas: Mustard gas was first used effectively in World War I by the German army against British and Canadian soldiers near Ypres, Belgium, in 1917 and later also against the French Second Army. The name "Yperite" comes from its usage by the German army near the
Action of 25 September 1917 about the new conditions produced by German defence-in-depth. The 4th Army had spread strong points and pillboxes in the areas between its defensive lines and made rapid counter-attacks with local reserves and "Eingreif" divisions ("Eingreifdivisionen", specialist counter-attack divisions), against Allied penetrations. Plumer issued a preliminary order on 1 September, which defined the Second Army area of operations as Broodseinde and the area to the south. The plan was based on the use of much more medium and heavy artillery, which had been brought to the Gheluvelt Plateau from VIII Corps, on the right flank of the Second Army and by