A mass submarine programme would trigger a response

Building the infrastructure and boats needed for a mass submarine force would not be a secret project. Britain would see the threat through intelligence, public information, or both, and could begin Flower-class corvette and Hunt-class destroyer programmes earlier rather than waiting for wartime losses. That reaction could preserve capital ships for the Mediterranean and Far East while giving Norway more escorts and putting multiple carriers into the Taranto raid. The counterfactual therefore includes the opponent's procurement response, which may turn Germany's larger submarine investment into an Allied advantage elsewhere.