Cruiser sonar and ASW role debate

Passive hydrophones, full ASDIC sets, destroyer screens, and aircraft served different purposes, so cruiser underwater sensors were never a simple measure of quality. Hydrophones chiefly warned of incoming torpedoes, while ASDIC could also hold a submarine contact for a destroyer to attack without broadcasting its own position. The Royal Navy's losses of Aboukir, Cressy, and Hogue made underwater warning a durable design priority. Treaty displacement still forced every navy to weigh that protection against other capabilities. U.S. cruisers more often operated inside destroyer screens and relied on visual torpedo wakes, making cruiser-mounted sonar less valuable to their doctrine. The choice depended on mission, formation, and weight allocation.