The anti-submarine technology race before 1943

Wartime escort improvements grew from a development cycle that had begun before 1939, with vigorous testing of anti-submarine systems under restricted budgets as early as 1932. Hedgehog and Squid addressed weaknesses in ASDIC-era attack methods, while the Leigh Light covered the final mile in which airborne surface-search radar could lose a submarine at night. The French-made Metox radar-warning receiver then alerted U-boats that radar was searching for them, a quick countermeasure to Allied detection. Centimetric radar shifted the danger back toward the submarine. Signals intelligence followed the same competitive pattern: the new Enigma system was eventually broken, while Germany read an Admiralty code that Britain did not change until 1943. The reason for that delay remains uncertain, with counterintelligence and bureaucratic failure both left open in the discussion.