Submarines advance without wartime operational selection

Technical progress continues because every major navy recognizes both the submarine threat and its offensive value. Germany may build relatively few boats while prestige surface programs consume its constrained budget, so a premature Type XXI-style leap is unlikely. Longer peacetime testing could expose defects in American Mark 13 and Mark 14 torpedoes before a major war, although bureaucracies might answer with a nominally new weapon rather than admitting the old one's faults. Growing air patrol and exercise pressure could push snorkels into service before full air-independent propulsion, while navies still value surface speed for reaching distant patrol areas. Growing escort fleets also force submarine designers to consider how their boats will survive denser sonar and radar coverage. Without sustained combat, doctrine remains diverse and exercise results may preserve concepts that battlefield selection would have discarded.