Why 1939 fleet planning cannot use 1945 hindsight

The counterfactual keeps decision-makers inside the knowledge and expectations of 1939, when capital ships remained useful and mature carrier aviation was not guaranteed. Aircraft that existed in 1939 did not offer the reach, payload, or operational maturity that wartime development would produce by 1945. Promising research remained separate from a deployable capability. War could accelerate and spread technologies already under development. Waiting decades for a possible replacement can leave a navy without the forces it needs now, especially when no one can be certain that the theoretical system will mature as expected.