In the Bay of Biscay, 40 miles off the Gironde Estuary, British submarine HMS Tuna sinks French tug Chassiron and attacks Italian submarines Brin and Bianchi without success. British submarine HMS Triton sinks in the Otranto Strait off Taranto, Italy (cause unknown). Italian cruisers Eugenio & Montecuccoli and destroyers Pigafetta, Da Recco, Pessagno & Riboty shell Greek forces on the Albanian coast near Corfu.
South Atlantic. 800 miles South of Cape Verde Islands, German cruiser Admiral Scheer captures British SS Duquesna carrying 3,500 tons of frozen beef and 15 million eggs from Argentina to Britain (91 crew and 8 passengers taken prisoner). Admiral Scheer’s captain Theodor Krancke allows Duquesna to radio for help before stopping her with shots across the bow, to distract Royal Navy from cruiser Admiral Hipper’s breakout from the Denmark Strait. Duquesna is held near Brazil to supply food to German raiders until scuttled on February 18 1941.
North Atlantic. Italian submarine Veniero stops Greek steamer Anastassia with a torpedo (18 crew killed). The wreck of Anastassia is allowed to drift away after 10 survivors are taken prisoner. U-100 sinks British SS Napier Star at 8.20 AM (59 crew & 12 passengers lost; 9 crew, 1 gunner & 4 passengers picked up by Swedish MV Vaalaren and landed at Liverpool on 23 December). U-96 hits Dutch tanker Pendrecht with 1 torpedo at 4.15 PM, tearing a 14m hole (the crew abandons ship but reboards when 2 other armed tankers arrive and keep U-96 at bay). British destroyer HMS Legion escorts Pendrecht to the Clyde for temporary repairs, arriving on 21 December, before going to USA for permanent repairs.
British minesweeping trawler HMT Refundo hits a mine and is taken under tow but sinks 1 mile off the coast of Suffolk, England, near Felixstowe (2 killed).
Hitler issues Führer Directive 21 for the invasion of Soviet Russia, codenamed Operation Barbarossa. The goal: "The German Wehrmacht must be prepared to crush Soviet Russia in a quick campaign."