Why did France choose the Dunkerque class's unusual main-gun calibre after using several different calibres in earlier dreadnoughts?
Short answerNo single definitive reason is offered, but the French appear to have selected the best weapon they believed could be ready in time.
NotesThere is no conclusive documentary answer in this discussion. The pattern of French dreadnought calibres suggests that the navy did not preserve one main-gun standard across every class. For Dunkerque, the practical choice may have been the best gun designers believed they could obtain on the required schedule. Timing and development risk remain a plausible interpretation rather than a proven institutional rule.