Chemical weapons in World War I in Palestine during the Second Battle of Gaza. Russia began manufacturing chlorine gas in 1916, with phosgene being produced later in the year. Most of the manufactured gas was never used. The British Army first used mustard gas in November 1917 at Cambrai, after their armies had captured a stockpile of German mustard gas shells. It took the British more than a year to develop their own mustard gas weapon, with production of the chemicals centred on Avonmouth Docks. (The only option available to the British was the Despretz–Niemann–Guthrie process). This was used first in September 1918 during the breaking
German Type IXA submarine The first U-boat to be laid down in the Bremen ship yards was "U-37", whose keel was laid down on 15 March 1937. The last U-boat to be laid down was , whose construction began on 15 September 1937. By November 1939, all eight submarines had been fully constructed and commissioned into the "Kriegsmarine". The Type IXA submarines were the first German submarines to have a double hull. This allowed for a greater chance of survival in the event of an attack and gave them better seaworthiness on the surface. The Type IXA submarines had a test depth of .