20 September 1941
Atlantic Ocean : Battle of OG-74 (Outbound Gibraltar) started whe n convoy was disvored by Luftwaffe FW-200 Condor aircraft that led U-Boats towards it. German submarine U-124 sank British ships Baltallinn and Empire Moat of Allied convoy OG-74 500 miles west of Brest, France at 2331 hours; 60 survivors were rescued by British rescue ship Walmer Castle. Meanwhile, a Martlet Mk II fighter of No. 802 Squadron from Royal Navy escort carrier HMS Audacity shot down a German Fw 200 C Condor aircraft attempting to shadow OG-74; it was the first kill by a British carrier-based aircraft.
Meanwhile German submarine U-552 sank two tankers and U-74 sank catapult armed merchant ship Empire Burton, all of Allied convoy SC-44, 200 miles east of Iceland between 0113 and 0327 hours; 102 survivors were rescued by British corvette HMS Honeysuckle.
German submarine U-111 sank British ship Cingalese Prince 500 miles east of Brazil; 57 were killed, 20 survived in lifeboats.
At 0327 hours, off east coast of Greenland, the 6,325-ton Norwegian motor tanker Barbro carrying 9,000 tons of petrol was torpedoed by German submarine U-552 (Kapitänleutnant Erich Topp). Two torpedoes hit the ship and she immediately burst into flames, trapping the 34 crew on board. Other ships in convoy SC-44 could only watch helplessly as she sank.
Gibraltar : Italian submarine Scirè launched three manned torpedoes into Gibraltar harbor, which sank tanker Fiona Shell (killing 1), damaged tanker RFA Denbydale, and damaged freighter Durham. All six Italian personnel manning the three torpedoes swam to Spain and would eventually return to Italy as heroes.
Libya : British minelaying cruiser HMS Abdiel and destroyers HMS Jervis, HMS Kimberley, and HMS Hasty delivered 1,000 troops and 120 tons of supplies to Tobruk, Libya after sundown. They departed for Alexandria, Egypt 30 minutes after arrival.
Lithuania , Baltics : British minelaying cruiser HMS Abdiel and destroyers HMS Jervis, HMS Kimberley, and HMS Hasty delivered 1,000 troops and 120 tons of supplies to Tobruk, Libya after sundown. They departed for Alexandria, Egypt 30 minutes after arrival.
UK : Enigma decryption in Bletchley Park gives British intelligence advance warning about German attack plans on Moscow