World War II Convoy Battles

The running engagements of the Battle of the Atlantic, 1939 to 1945, fought around the trade convoys between North America and Britain. Numbered series such as the HX and SC eastbound and ON westbound convoys crossed against U-boat wolfpacks; set-piece battles included convoy SC 7 (October 1940) and the climactic ONS 5 in May 1943, where escorts and aircraft sank seven U-boats and turned the campaign. Victory came from escort carriers, very-long-range Liberator aircraft, HF/DF, centimetric radar, and Ultra signals intelligence, not from any single weapon.