World War II priorities varied by navy

Which three ship classes should the major navies have prioritized for World War II?

Germany needed more destroyers, while Italy and Japan needed better escort and cruiser choices. Japan's greater weakness was replacing trained personnel and retaining institutional memory.

This is a compressed comparison rather than a universal recipe. Germany's clearest need is large numbers of destroyers, while Italy should turn useful designs such as the Capitani Romani class into numbers, complete the remaining Littorio-class ships, and field a sound destroyer. Japan needs an inexpensive escort, a balanced escort or strike carrier, and a viable torpedo-oriented cruiser, but those purchases do not fix its deepest weakness. Its best aviators and other veterans must rotate home to train replacements and preserve institutional memory instead of being consumed at the front. The comparison shows why class choice only works when the personnel and training system can reproduce combat effectiveness.