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
German Type UC III submarine German Type UC III submarine Type UC III minelaying submarines were used by the Imperial German Navy () during World War I. They displaced at the surface and submerged, carried guns, 7 torpedoes and up to 14 mines. The ships were double-hulled with improved range and sea-keeping compared to the UC II type. The type had better seagoing, maneuvering and turning capabilities than its predecessor, while underwater stability was reduced. A total of 113 Type UC III submarines were ordered by the Imperial German Navy, but only 25 U-boats were completed before the Armistice with Germany in 1918. Of those,