Submarine war shifts from quantity to technology

At the war's outset, too few escorts left merchant shipping exposed before German submarine numbers and tactics fully developed. A large prewar sloop force could blunt that numerical crisis and force submarines to confront organized protection earlier. It would not solve submarine warfare permanently because later stages still became a contest of sensors, weapons, and countermeasures. The earlier Type XXI example makes the distinction concrete: a later technological advance would demand a counter, but that future challenge did not excuse the avoidable early shortage of escort hulls. The failure came from avoiding a foreseeable problem whose threat and affordable response were already understood.