The Admiral Hipper slips out of Brest for another sortie into the Atlantic.
The Battleships Scharnhorst and Gneisenau sail from the Baltic to the Atlantic, causing absolute havoc to shipping routes and timetables.
U-47, commanded by top ace Günther Prien, hero of Scapa Flow, is sunk by the British Destroyer HMS Wolverine.
The Kriegsmarine loses two of its most successful U-boat commanders, Kretschmer (U-99) and Schepke (U-100) to British escorts from convoy HX112.
Churchill forms the 'Battle of the Atlantic' committee in order to afford the highest level of co-ordination against the U-boat menace.
During an attack against convoy OB318, U-110 commanded by Julius Lemp suffers serious damage and is forced to surface and scuttle. Unfortunately for the Germans, the scuttling charges failed to detonate, allowing the British destroyer HMS Bulldog to put across a boarding party and seize an enigma machine and other vital secret material. The British put U-110 under tow, but the damaged U-boat later sinks. The German raider Penguin is sunk by HMS Cornwall off the Seychelles Islands in the Indian Ocean.
The German battleship Bismarck and the heavy cruiser Prinz Eugen leave Gotenhafen in the Baltic to begin operations against British convoys in the Atlantic (Operation Rheinübung).
Egyptian liner Zamzam reported sunk by Germans in the South Atlantic, passenger list included over 200 Americans.
Against strict orders not to attack American vessels, the US merchant ship Robin Moor is sunk by U-69 (Kptlt. Metzler). This sinking of a neutral American vessel is publicly denounced by President Roosevelt and becomes yet another argument for him in his secret desire for bringing the United States into war against Germany. An RAF reconnaissance plane sight the Bismarck and Prinz Eugen in the port of Bergen, allowing the British Home Fleet time to ready plans to intercept them in the earlier hours of the 22nd May.
British blockade of Vichy France made complete.
During the evening, the cruiser HMS Suffolk sights the Bismarck and Prinz Eugen in the Denmark Straight. The Home Fleet makes ready to intercept at dawn on the 24th May.
The German battleship Bismarck, supported by the heavy cruiser Prinz Eugen, sinks the British battle cruiser Hood after firing only three salvoes. There are only 3 survivors out of a crew of 1,421. The Prince of Wales is also damaged and forced to break off the action.
Bismarck escapes the Royal Navy’s pursuit and separates from the Prinz Eugen and makes her way to Brest.
British flying boat spots the Bismarck at 10:36am. Swordfish Torpedo-bombers from the Ark Royal score hits on the Bismarck, disabling her steering gear and rendering her un-maneuverable. This enables British destroyers to attack after dark.
400 miles west of Brest, the crippled Bismarck is relentlessly bombarded by dozens of British warships, including the battleships Rodney and King George V. After all her guns are silenced, she is sunk by torpedo's from the cruiser Dorsetshire. There are only 110 survivors out of a crew of 2,300. The convoy HX129, becomes the first to have continuous escort protection across the Atlantic.
The heavy cruiser Prinz Eugen arrives in Brest.
The first of five heavy night raids by the RAF begins on Brest as Prinz Eugen shelters there.
The German pocket battleship Lützow (formerly Deutschland) is attacked and damaged by RAF aircraft off the southern coast of Norway.
29 People Killed, when German dive-bombers sink the Great Western Railway steamer St. Patrick.
US Navy takes over patrolling convoy routes in the North Atlantic and tracking German submarines for the Royal Navy in violation of Neutrality Act.
German submarines sink a Norwegian and 3 British ships from the Convoy OG-71 of 22 ships and 9 escorts in the Atlantic Ocean.
First Arctic convoy leaves Iceland for Russia.
U-652 attacks the US destroyer Greer off Iceland after being tracked and harassed by it.
British convoy SC-42 (64 ships), sailing from Sydney to the Britain is attacked by a wolf pack of 19 U-boats just south of Greenland between the 10th and 14th September. SC-42 loses 17 merchant ships for 69,813-tons. 2 U-boats, U-207 and U-510 are sunk in return.
The US Navy begins to take over the convoying of British ships as far as Iceland, which is seen as an un-neutral act by the German government.
The first Arctic bound for Russia leaves Britain. It consists of ten merchantmen with escorts and was designated as PQ1.
Churchill gives a personal undertaking to Stalin to send a convoy every ten days to Russia's northern ports.
Destroyer USS Kearny damaged by German torpedo off Iceland.
The US destroyer Reuben James escorting Convoy HX-156 is sunk by U-552 (Kapitänleutnant Erich Topp) with the loss of 100 of her crew. The destroyer is the first US naval casualty in the hitherto undeclared war between Germany and the United States that has existed after President Roosevelt authorised the use of American naval vessels to escort Lend-Lease convoys bound for Britain.
The German government issues a statement denying the charges made by President Roosevelt that the US destroyers Greer and Kearney were attacked by German submarines without any provocation; that the exact opposite was true in that the U-boats fired torpedoes only after they were tracked and depth-charged for hours by these US vessels.
The German blockade runner 'Odenwald' which is disguised as a US merchant, is captured by the US cruiser Omaha and the destroyer Somers.
All operational U-boats ordered to proceed to the Mediterranean or its approach.
Hitler lifts the ban on U-boats operating in US territorial waters, two days before he declares war on the USA. This was to allow Dönitz to deploy 5 U-boats along the USA's eastern seaboard in order to be available for immediate action when the declaration of war was made.
Convoy HG76 (32 ships), sets sails from Gibraltar with heavy escort.
Admiral Royal E. Ingersoll takes over command of the Atlantic Fleet, from Admiral Ernest J. King who is appointed as Commander, US Navy.
Allied merchant shipping sunk by U-boats, world-wide from January to year's end 1941 is 503 ships, equalling 2,530,011 gross tons. 35 U-boats were lost worldwide in the same period.