1941 U-boats sink four ships from convoy HX 121. May May 8, 1941 U-boats sink five ships from convoy OB 318. May 11, 1941 Aircraft sink Somerset from convoy SL 72. May 14, 1941 Aircraft sink Karlander from convoy OB 321. May 20, 1941 U-boats sink nine ships from convoy HX 126. sinks Starcross from convoy SL 73. May 21 or 22, 1941 , , and three escorting destroyers leave Bergen and head toward the Arctic Ocean. May 24, 1941 Bismarck and Prinz Eugen intercept the path of battleship and battlecruiser ; Battle of Denmark Strait begins. Bismarck sinks HMS Hood then badly damages Prince of Wales, forcing it to retreat. May 27, 1941. Bismarck sunk. June June 1, 1941 The United States Coast Guard begins the Greenland Patrol. June 11, 1941 Aircraft sink Baron Carnegie from convoy OB 334. June 13, 1941 sinks Djurdjura and Eirini Kyriakidou from convoy SL 76. Newfoundland Escort Force is created under the command of Admiral Murray based at St John's Newfoundland, to provide escort cover from the coast of Canada to Iceland. June 24, 1941 sinks Schie and Kinross from convoy OB 336. U-boats sink five ships from convoy HX 133. June 26, 1941 U-boats sink four ships from convoy SL 78. July July 7, 1941 President Roosevelt announces that US warships will henceforth protect US merchant vessels in the North Atlantic, and the US effectively joined the Battle of the Atlantic. August August 5, 1941 U-boats sink five ships from convoy SL 81. September September 10, 1941 While U-boats sink fifteen ships from convoy SC 42, Canadian corvettes and sink by depth charges and ramming in the Denmark Strait south of Tasiilaq, Greenland. This is Canada's first U-boat kill of the Battle of the Atlantic. September 15, 1941 Aircraft sink Daru from convoy SL 85. September 19, 1941 is the first Canadian corvette sunk during the war. Levis is hit by a torpedo while escorting Convoy SC 44 off the coast of Greenland. Four merchant ships are also sunk from the convoy by U-boats. September 22, 1941 U-boats sink seven ships from convoy SL 87. October October 16, 1941 U-boats sink nine ships from convoy SC 48. October 21, 1941 sinks Serbino and Treverbyn from convoy SL 89. October 31, 1941 torpedoes , which was escorting Convoy HX 156. Reuben James is the first United States warship sunk during World War II.