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
Actions of 30 September – 4 October 1917 diary note that it had been an awful experience; he did not know what to do against the British. Erich Ludendorff the (Quartermaster-General of the German Army, equivalent to the British Chief of the General Staff) conferred on 29 September with (field marshal) Crown Prince Rupprecht the commander and (lieutenant-general) Hermann von Kuhl the chief of staff, of "Heeresgruppe Kronprinz Rupprecht von Bayern" (Army Group Rupprecht of Bavaria), the 4th Army commander, General Sixt von Armin and the 4th Army chief of staff, (major-general) Fritz von Loßberg. The staff officers of the 4th Army (corps headquarters) agreed that defensive manoeuvres