This is a timeline for the Battle of the Atlantic (1939–1945) in World War II.
1939
August August 19, 1939 Five U-boats sail from Kiel and nine from Wilhelmshaven to take waiting positions in the North Atlantic.Rohwer & Hummelchen, p.1 August 21, 1939 German "pocket battleship" sails from Wilhelmshaven for a South Atlantic cruise. August 24, 1939 German "pocket battleship" sails from Wilhelmshaven for a North Atlantic cruise.
September September 3, 1939 sinks the . This attack is interpreted by the United Kingdom as the start of unrestricted submarine warfare. However, in Germany it leads to stricter controls being issued by the Kriegsmarine. Germany at this point had 39 of its 58 U-boats at sea, but this was far less than the 300 which Admiral Karl Dönitz, chief of German submarine forces, considered to be necessary before the opening of war. September 5, 1939 stops, evacuates and sinks the German freighter Inn off the Canary Islands. September 7, 1939 The first convoys sail outbound from the British Isles: OA from the English Channel, OB from Liverpool, and OG to Gibraltar.Rohwer & Hummelchen, p.3 September 14, 1939 The first of the SL convoys sails from Freetown. attacks the British aircraft carrier , but fails to cause any damage. The aircraft carrier's escorts force U-39 to the surface with depth charges and the crew are taken prisoner.Rohwer & Hummelchen, p.2 September 16, 1939 The first Allied convoy sets sail from Halifax, Nova Scotia. Convoy HX 1 contains 18 merchant ships and is escorted by and to an Atlantic rendezvous with Royal Navy ships and .Rohwer & Hummelchen, p.4 September 17, 1939 sinks the Royal Navy aircraft carrier . September 17, 1939 The first Allied "fast convoy" HXF 1 sets sail from Halifax escorted by HMCS Fraser formerly . September 20, 1939 is sunk with depth charges from the British destroyers and . September 26, 1939 German media reports the sinking of the British aircraft carrier . However, this report is false: many such reports would be made during the war. September 30, 1939 German "pocket battleship" sinks the first merchant ship of its cruise. Total sinkings for its sortie will total nine vessels of 50,000 tons before it becomes embroiled in the Battle of the River Plate.
October October 5, 1939 German "pocket battleship" sinks the first merchant ship of its cruise. October 14, 1939 , under Kapitänleutnant Günther Prien, penetrates the British naval base at Scapa Flow, sinking at anchor. October 16, 1939 Germany begins employing magnetic mines. These cause significant losses to Allied shipping. October 18, 1939 Germany authorizes submarine attacks against any passenger vessel in a convoy or without lights. President Roosevelt closes U.S. ports and navigable waters to any belligerent submarines.Wagner, p.74 October 27, 1939 sinks Malabar from convoy HX 5.Hague, p.130 October 30, 1939 sinks Bronte from convoy OB 25.Hague, p.155
November November 21, 1939 British light cruiser hits a German mine, and is seriously damaged while operating in the Firth of Forth. November 23, 1939 A German magnetic mine is recovered successfully by the Allies, leading to the development of effective countermeasures. The German battleship sinks the British armed merchant vessel . The Scharnhorst and the accompanying are forced to abandon their sortie and return to port. November 25, 1939 sinks Royston Grange from convoy SL 8.Hague, p.145
December December 4, 1939 First U-boat lost to an Allied submarine in the war when sinks outside Kristiansund in Norway. December 5, 1939 sinks Navasota from convoy OB 46. December 9, 1939 Orion and Widder, first two German auxiliary cruisers, were commissioned. December 10, 1939 The first Allied troop convoy TC 1 sets sail from Halifax with 7,400 men of the 1st Canadian Infantry Division. December 14, 1939 Battle of the River Plate - Admiral Graf Spee scuttled after battle with HMS Exeter, HMS Achilles and HMNZS Ajax
1940
January January 30, 1940 sinks Vaclite and Keramiai from convoy OA 80G.Hague, p.149
February February 5, 1940 sinks Beaverburn from convoy OA 84. February 14, 1940 The United Kingdom announces armaments will be carried by all passenger ships. Germany responds by announcing that all vessels will be considered warships.
March March 16, 1940 A German air raid at Scapa Flow damages a cruiser and causes the first civilian casualties in Britain of the war. April
April 9, 1940 Action off Lofoten - brief encounter between Scharnhorst, Gneisenau vs HMS Renown and her destroyer screen. After brief exchange of fire, German battleships disengaged.
June June 8, 1940 Operation Juno: HMS Glorious sunk by Scharnhorst and Gneisenau. She became the first aircraft carrier sunk by battleships in naval combat June 12, 1940 sinks Willowbank and Barbara Marie from convoy SL 34. June 14, 1940 sinks Italia and Erik Boye from convoy HX 47. June 22, 1940 sinks San Fernando from convoy HX 49. June 25, 1940 sinks Saranac and Windsorwood from convoy OA 172. Canada loses its first navy vessel during an accident off the coast of France, when is cut in two by Royal Navy cruiser , with 45 lives lost aboard the Fraser and 19 aboard Calcutta. June 30, 1940 U-boats sink two ships from convoy SL 36.
July July 2, 1940 Aircraft sink Aeneas from convoy OA 177G. July 4, 1940 Aircraft and E-boats sink five ships from convoy OA 178. July 8, 1940 sinks Humber Arm from convoy HX 53. July 10, 1940 sinks Alwaki from convoy OA 179. July 17, 1940 U-boats sink Manipur and Scottish Minstrel from convoy HX 55. July 26, 1940 sinks four ships from convoy OB 188. July 28, 1940 Auxiliary cruiser Thor encountered armed merchant cruiser HMS Alcantara and managed to escape. July 31, 1940 sinks Jersey City from convoy OB 191.
August BETASOM base opens in Bordeaux for Italian submarine patrols into the Atlantic. August 4, 1940 sinks 3 British merchant steamships from convoy HX 60. August 5, 1940 sinks Boma from convoy OB 193. August 15, 1940 A new system of SC convoys is initiated between Canada and the British Isles, to provide convoy protection for slow ships. August 16, 1940 sinks Hedrun from convoy OB 197. August 23, 1940 sinks Cumberland and St. Dunstan from convoy OB 202. Aircraft sink Llanishen and Makalla from convoy OA 203. August 24, 1940 sinks Blairmore from convoy SC 1.Hague, P.136 August 25, 1940 Convoy HX 65 comes under attack by U-boats and aircraft sinking five ships.Hague, p.131 August 28, 1940 U-boats sink four ships from convoy HX 66. sinks Dalblair and Astra II from convoy OA 204. August 30, 1940 torpedoes San Gabriel from convoy OB 205. August 31, 1940 British destroyers and are sunk and two other ships damaged by mines in the Texel Disaster with the loss of 300 killed and 100 wounded or taken prisoner.
September September 2, 1940 sinks Thornlea from convoy OB 206. September 4, 1940 sinks Titan from convoy OA 207. September 6, 1940 Aircraft sink St. Glen from convoy SL 44. September 8, 1940 U-boats sink two ships from convoy SC 2. September 15, 1940 sinks Alexandrios and Empire Volunteer from convoy SC 3. Aircraft sink Nailsea River from convoy SL 45. September 17, 1940 sinks Tregenna from convoy HX 71. September 18, 1940 sinks Marina and City of Benares from convoy OB 213. September 20, 1940 sinks four ships from convoy OB 216. September 21, 1940 U-boats sink six ships from convoy HX 72. September 26, 1940 sinks Manchester Brigade and Stratford from convoy OB 218. September 27, 1940 Aircraft sink Port Denison from convoy OA 220. September 28, 1940 Aircraft sink Dalveen from convoy HX 73. sinks Empire Ocelot from convoy OB 218.
October October 9, 1940 sinks three ships from convoy SC 6. October 11, 1940 U-boats sink six ships from convoy HX 77. October 14, 1940 sinks Hurunui from convoy OA 228. October 15, 1940 sinks Bonheur from convoy OB 228. October 17, 1940 sinks Dokka and Uskbridge from convoy OB 228. October 18, 1940 Minelaying begins on the Allied Northern Barrage minefield between Scotland and Greenland. October 19, 1940 U-boats sink ten ships from convoy HX 79 and fifteen ships from convoy SC 7. October 22, 1940 , recently acquired to replace , is sunk in a collision with the freighter 480 km west of Ireland. 142 men are lost, including the captain and four other officers.
November November 5, 1940 German "pocket battleship" sinks five ships from convoy HX 84 and the escorting armed merchant cruiser . sinks Scottish Maiden from convoy HX 83. November 6, 1940 Aircraft sink Nalon from convoy SL 52F. November 15, 1940 Aircraft sink Apapa from convoy SL 53. November 21, 1940 sinks Daydawn and Victoria from convoy OB 244. November 22, 1940 sinks King Idwal from convoy OB 244. November 23, 1940 sinks six ships from convoy SC 11.
December December 1, 1940 U-boats sink nine ships from convoy HX 90. is the first Canadian naval vessel hit by torpedo in the Battle of the Atlantic, attacked 300 miles west of Ireland by a submarine while escorting Convoy HG 47. December 5, 1940 Auxiliary cruiser Thor encountered armed merchant cruiser HMS Carnarvon Castle and heavily damaged it in brief exchange of fire December 11, 1940 sinks three ships from convoy HX 92. December 24, 1940 Convoy WS 5A attacked by Admiral Hipper, but cruiser escort of HMS Berwick and two light cruisers drove her off December 27, 1940 Italian submarine Enrico Tazzoli sinks Ardanbhan from convoy OB 263.
1941
January January 16, 1941 Aircraft sink two ships from convoy OB 274. January 22, 1941 Operation Berlin: a sortie of Scharnhorst and Gneisenau into North Atlantic resulting in 22 sunk or captured merchant ships January 29, 1941 sinks three ships from convoy SC 19.
February February 12, 1941 sinks seven ships from convoy SL 64S. February 19, 1941 Aircraft sink three ships from convoy OB 287. February 24, 1941 sinks three ships from convoy OB 289. February 26, 1941 Aircraft sink eight ships from convoy OB 290. February 27, 1941 sinks Kasongo and Borgland from convoy OB 290.
March March 1, 1941 sinks Cadillac from convoy HX 109. Aircraft sink Rotula from convoy SC 22. March 7, 1941 U-boats sink three ships from convoy OB 293. March 8, 1941 U-boats sink five ships from convoy SL 67. March 13, 1941 Aircraft sink Empire Frost from convoy SC 23. March 16, 1941 sinks five ships from convoy HX 112. March 17, 1941 U-boats sink six ships from convoy SL 68. March 19, 1941 Aircraft sink Benvorlich from convoy OB 298. March 22, 1941 Operation Berlin ends by Scharnhorst-class battleships arriving in occupied France March 29, 1941 sinks three ships from convoy HX 115.
April April 1, 1941 Aircraft sink two ships from convoy HX 114. April 3, 1941 U-boats sink six ships from convoy SC 26. April 4, 1941 Auxiliary cruiser Thor sighted and destroyed armed merchant cruiser HMS Voltaire in combat April 6, 1941 Aircraft sink Dunstan from convoy OB 306. April 9, 1941 The United States occupies Greenland. April 16, 1941 Aircraft sink Swedru from convoy SL 69. April 28, 1941 U-boats sink four ships from convoy HX 121.
May May 8, 1941 U-boats sink five ships from convoy OB 318.
Auxiliary cruiser Pinguin was sunk by HMS Cornwall, becoming first German auxiliary cruiser lost in World War Two 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.Hague, p.132 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 intercepted by battleship and battlecruiser ; Battle of Denmark Strait begins. Bismarck sinks HMS Hood, then badly damages HMS Prince of Wales, forcing it to retreat. May 27, 1941.