Escort orders and the 1938 answer

Britain's 1938 orders for Flower-class corvettes and Hunt-class escort destroyers created the material base that later protected convoys. Submarines took longer to build and crew than the escorts opposing them, so the prewar construction decision shaped force ratios years later. An attack on an escorting trawler might consume two or three torpedoes intended for merchant ships while revealing the submarine's position. Early ASDIC and depth-charge attacks often required several escorts to maintain contact and prosecute one target. Ahead-throwing weapons improved that exchange while British yards continued producing escort hulls.