Chemical weapons in World War I volatile oily liquid. It was introduced as a vesicant by Germany in July 1917 prior to the Third Battle of Ypres. The Germans marked their shells yellow for mustard gas and green for chlorine and phosgene; hence they called the new gas "Yellow Cross". It was known to the British as "HS" ("Hun Stuff"), and the French called it "Yperite" (named after Ypres). Mustard gas is not an effective killing agent (though in high enough doses it is fatal) but can be used to harass and disable the enemy and pollute the battlefield. Delivered in artillery shells, mustard gas was
Tanks in the German Army the Anglo-Canadian forces of the 21st Army Group; and the numerous battles to secure the town became collectively known as the Battle of Caen. US forces in the meantime, engaged mainly the "Panzer Lehr" Division, and the Panther tank proved to be most effective when fighting in open country and shooting at long range—its combination of superior armor and firepower allowed it to engage at distances from which the American M4 Shermans could not respond. The Tiger was first used in action on 23 September 1942 near Leningrad. Under pressure from Hitler, the tank was put into action months earlier