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 U 93 submarine German Type U 93 submarine Type 93 was a class of U-boats built during World War I by the Kaiserliche Marine. Type 93 U-boats carried 16 torpedoes and had various arrangements of deck guns. As with the type 81 and 87, some had only one SK L/30 deck gun while others had a single SK L/45 gun and some were initially equipped with both. In 1917 some of the boats were refitted with a single 10.5 cm gun and 220 rounds. These boats carried a crew of 39 and had excellent seagoing abilities with a cruising range of around .