German naval forces announce a blockade of Sweden's Gothenburg harbour to protest the ongoing traffic between Sweden and Great Britain. After five months, the Germans finally relent and lift the blockade.
Admiral Dönitz takes over from Admiral Raeder as C-in-C of the German Navy.
Convoy ON-166 (60 ships) sailing from Britain to North America, is attacked in the North Atlantic by 19 U-boats from wolfpacks Ritter and Knappen between the 21st and 26th February. 14 allied ships are lost for 87,901 tons. 4 U-boats U-225, U-606, U-529, U623 were sunk during the battle.
A new wolfpack, codenamed 'Raubgraf' (Robber Baron), is created in the central North Atlantic. It will operate between the 7th and 20th March 1943 and includes U-84, U-89, U-91, U-435, U-468, U-600, U-603, U-615, U-621, U-638, U-653, U-664, U-758. Immediately the wolfpack attacks convoy ON-168 which is traveling between North America and the UK. One ship is damaged and abandoned on the 7th March, to be finally sunk on the 12th March for 6,537 gross tons.
U-510 torpedoes eight ships in three hours off the coast of Brazil, in what is the most successful single U-boat action of the war.
The north Atlantic convoy ONS-169 is attacked by wolfpack 'Raubgraf' between the 11th and 12th March losing 2 ships for 10,531 gross tons. Atlantic convoys SC121 and HX228 are also attacked by other wolfpacks and lose 17 ships for the loss of just U-444 and U-432.
Wolfpack 'Raubgraf' and attacks convoys HX-229 (37 ships) between until the 19th March, sinking 12 ships for 86,326 gross tons damaging 4. Another wolfpack, named 'Stürmer', attacks SC122 and over a period of four days and nights sinking 11 ships (54,740 tons) for the loss of just one U-boat, U-384 (Oblt. von Rosenberg-Gruszinski).
On his last patrol aboard U-404, Kapitänleutnant Otto von Bülow fires two FAT and two G7e torpedoes at British aircraft carrier HMS Biter. All detonate prematurely and HMS Biter escapes without damage. Von Bülow is later decorated by Hitler with Oak leaves to his Knights Cross for his Atlantic successes and German newspapers report the recent sinking of the American carrier USS Ranger as well. Later, USS Ranger commander Gordon Rowe, is photographed aboard his carrier smiling at a photograph of von Bülow and the German report of his vessel's demise.
U-boats begin a six-day attack on Convoy ONS5, during which 13 allied ships are finally sunk for the loss of six U-boats.
During a raid against Kiel by the U.S. 8th Air Force, 3 U-boats are destroyed.
The U.S. Tenth Fleet is formed for anti-submarine operations in the Atlantic.
The battle of the Atlantic is officially concluded as won by Allies, due to the withdrawal of virtually all U-boats from the Atlantic by Admiral Dönitz, C-in-C of the Kriegsmarine after the loss of 56 boats in April and May.
By the end of May, 41 U-boats have been sunk in the Atlantic due to greatly improved allied anti-submarine techniques and tactics (Hedgehog, greater-range patrol aircraft, better radar, more escort vessels and carriers, plus the advantage of having broken the German Navy Enigma code). "Black May" effectively marks the end of a sustained German U-boat campaign in WW2 which did come very close to starving out Britain and forcing her to make terms with Germany.
BdU (C-in-C U-boats) adopts a new policy of fighting back at Allied sub-hunting aircraft with the U-boats' own AA guns while crossing the Bay of Biscay on the surface. This tactic proves to be largely unsuccessful and is soon abandoned.
U-513 (Kptlt. Sohler) sinks 4 ships off the coast of Brazil.
RAF Coastal Command begins daily patrols over the Bay of Biscay with aircraft equipped with new detection devices to locate and destroy German U-boats leaving and entering their bases on the French coast.
The British battleships Valiant and Warspite are transferred from Scapa Flow to Oran and Alexandria in North Africa in preparation for Operation Husky, the Allied invasion of Sicily.
The British announce a five-day U-boat attack on the Atlantic convoys and claim that 97% of ships survived.
Off the coast of Brazil, U-185 (Kptlt. Maus) sinks 3 merchant ships.
The Japanese submarine I-8, reaches France after a marathon voyage from Penang in Malaya.
Molotov insists on the resumption of Arctic convoys.
Six British midget submarines attack and damage the Tirpitz in Alten Fjord, northern Norway.
A German torpedo boat flotilla sinks the Royal Navy cruiser Charybdis and the destroyer Limborne in a Channel duel.
An E-boat attack on a convoy off the Norfolk coast result in four E-boats being sunk and one British trawler.
A hospital ship arrives in Liverpool with 790 wounded POW's aboard, repatriated from Germany.
Ordered to sail to the Barents Sea and destroy the allied convoy JW-55B bound for the Soviet port of Murmansk, the German battle-cruiser Scharnhorst encounters a protective force of the British Home Fleet consisting of the cruisers HMS Belfast, Duke of York, Jamaica and Norfolk. After a fierce action, Scharnhorst is sunk, with only 36 of her crew of 1,839 surviving.
The Royal Navy cruisers Enterprise and Glasgow sink the German destroyers T25, T26 and Z27 which were escorting blockade runners in Bay of Biscay.
Allied merchant shipping sunk by U-boats, world-wide from January to year's end 1943 is 588 ships, equalling 3,042,371 gross tons. 242 U-boats were lost worldwide in the same period.