Air Operations, Europe

British bombers carry out a heavy raid on Bremen.

In a reprisal for the Hamburg raid the Germans attempt to hit the Rolls-Royce aircraft engine factory in the East Midlands. Radio Berlin reports extensive damage but the truth is that just a few farm animals are killed in the bombardment.

Air Operations, North Africa

There is a British air raid on Derna.

Battle of the Atlantic

U-Boat Capture

On May 9, 1941 the German submarines U-110 and U-201 were attacking a British convoy in the Atlantic south of Iceland. U-110 was forced to surface after being depth changed and was abandoned by her crew who thought that the submarine was sinking. A boarding party from the British destroyer Bulldog boarded the submarine and carried off its code books, ciphers and a Naval Enigma machine. The Enigma machine and the documents allowed Alan Turing and his codebreakers at Bletchley Park to break the German Naval Enigma code, an intelligence breakthrough which changed the course of the war in the Atlantic.

• In an attack on Convoy OB-318 U-110 sinks the British steamers Esmond (4976t) and Bengore Head (2609t) east of Cape Farewell. All 50 of the crew of the Esmond are rescued. 1 crewman is lost on the Bengore Head, 40 survivors are picked up by the Norwegian steamer Borgfred and the British corvette Aubretia. After sinking 2 ships from the convoy, U-110 under the command of Lt-Cdr Fritz Julius Lemp is forced to surface by a depth-charge attack from the British corvette Aubretia and destroyers Bulldog, Broadway and Amazon. She is then boarded and captured. Code books and an Enigma cipher machine are recovered. As well as providing useful information for general code breaking work, in this case the books are of considerable use in the imminent operations involving the Bismarck and her supply ships. The Bulldog takes the submarine in tow. The commanding officer and 14 of the crew are lost in the incident. 32 of the crew are rescued. U-110 sinks on May 11.
• U-201 sinks the British steamer Gregalia (5802t) from the same convoy east-northeast of Cape Farewell. Her crew of 66 are picked up by the British anti-submarine trawler Daneman.
• The British mine destructor ship Queenworth (3010t) is sunk by German bombing east of Outer Dowsing Light Buoy. No crew are lost.
• The French steamer Criton (4564t) is seized by the British armed merchant cruiser Cilicia off Freetown.
• The Italian submarine Tazzoli sinks the Norwegian tanker Alfred Olsen (8817t) west of Freetown. The entire crew are rescued.
• U-103 sinks the British steamer City of Winchester (7120t) about 400 miles south-southwest of the Cape Verde Islands with the loss of 6 of her crew. 96 survivors are picked up by the Norwegian steamer Herma.

Italian East Africa

British pressure increases in all sectors of the Amba Alagi front.

Mediterranean

1 of the TIGER transports sinks on a mine. Force H begins to return to Gibraltar.

North Africa

The situation around Tobruk remains unchanged as the two sides exchange artillery fire.