Day 1117 September 21, 1942

8 miles off Mehedia, Tunisian, British submarine HMS Unruffled sinks Italian auxiliary minesweeper Aquila with the deck gun at 1.05 AM and Vichy French merchant Liberia (previously Greek Cape Corso) with torpedoes.

At 6.40 AM 20 miles off the coast of British Guyana, U-175 sinks Yugoslavian SS Predsednik Kopajtic (3 dead, 25 survivors.

At 11.14 AM between Greenland and Jan Mayen Island, U-606 approaches convoy QP-14 but is attacked by a Norwegian Catalina floatplane (330 Sqdn RAF/Z, pilot Lt C.J.A. Stansburg) with 4 depth charges that cause little damage. U-606 shoots down the Catalina (all 8 crew including 2 wounded are rescued by British destroyer HMS Marne).

Training U-boat U-446 sinks on a mine in the Gulf of Danzig. U-446 will be raised in November but decommissioned and used as a hulk for tests.

British rescue tug HMS St. Olaves runs around off Duncansby Head, Scotland, and is declared a total loss.

On the Kokoda Track, Papua, Japanese begin to retreat from Ioribaiwa, out of supplies including food and diseased with malaria and dysentery. Resupply is almost impossible from Buna on the coast over the 13,000 feet high Owen Stanley mountain range (which is dominated by Allied aircraft) and reinforcements will not be coming as all available Japanese troops are being diverted to Guadalcanal. Meanwhile, Australians at Port Moresby do receive reinforcements in the shape of Australian 16th Infantry Brigade.

55 miles South of Japanese naval base at Truk Lagoon, US submarine USS Trout sinks Japanese auxiliary net layer Koei Maru.

85 miles East of Shanghai, China, US submarine USS Grouper sinks Japanese merchant Tone Maru.