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
6th Army (German Empire) eventually come to be regarded as one of Germany's most able generals. On 24 September 1915 the 6th Army was the target for the British Army's first chlorine gas attack of the war. Despite the horrific casualties inflicted, the British offensive became bogged down after several days. Rupprecht was promoted to the rank of field marshal ("Generalfeldmarschall") in July 1916 and assumed command of Army Group Rupprecht on 28 August that year, consisting of the 1st, 2nd, 6th and 7th Armies. Following Rupprecht's promotion, command of the 6th Army was given to General Ludwig von Falkenhausen. In March 1917 the