in the Atlantic and the later American submarine campaign in the Pacific. Germany did not depend on heavy mercantile traffic the way Britain was dependent on overseas trade, and thus there were no unprotected convoys or mercantile traffic for the British submarines to ravage. Most German mercantile traffic was confined to the North Sea, which was heavily mined. Thus, British submarines were obliged to undertake long, often fruitless patrols in these confined, dangerous waters. Norway On 10 September 1939, nine days after the war began, Triton sighted another submarine while on patrol off the coast of Norway. When the submarine failed to respond to challenges, she fired two torpedoes from the external bow tubes, hitting the submarine with one and sinking it. Unfortunately, this submarine turned out to be the Oxley, the first British submarine to be lost during the war, with only two of her crew surviving the attack. The crew of the Triton was exonerated by a subsequent inquiry, but it was an inauspicious start to the war for the T-class submarine fleet. Triumph was unfortunate enough to run into a mine on 26 December 1939 that blew off her bow section, but miraculously survived and was able to return to Rosyth for extensive repairs. With the start of the Norwegian Campaign in April 1940, increased Kriegsmarine traffic in support of the German invasion led to more action for the T-class submarines based in the North Sea. On 8 April 1940, Triton encountered the German cruisers Blücher and Lützow but missed with a full salvo of ten torpedoes. Two days later, she had more success after reloading, sinking three ships in a German convoy with six torpedoes. Truant also achieved a notable success, hitting and disabling the cruiser Karlsruhe, which had to be finished off by an escorting torpedo boat. Two T-class boats were lost during the Norwegian campaign: Thistle (torpedoed by U-4 on 10 April 1940) and Tarpon (depth-charged by Q-ship Schiff 40/Schürbek on 14 April 1940). Bay of Biscay The British began establishing submarine patrols in the strategic Bay of Biscay, known as the 'Iron Ring', in July 1940 after the fall of France and the German occupation of the French Atlantic ports. These became much more important once heavy German warships like the Scharnhorst, Gneisenau, and Prinz Eugen arrived there in 1941. On 15 December 1940, Thunderbolt torpedoed the Italian submarine , the first of