How did the Royal Navy arrive at a 1925 estimate of 25 cruisers for trade protection?
Short answerIt compared trade routes and patrol areas with the demands of a particular war scenario. The broader cruiser total also included fleet duties and maintenance allowances.
NotesThe Admiralty continuously mapped maritime trade and used likely patrol areas to estimate cruiser requirements for particular wars. The 25-cruiser figure belonged to one scenario, with other opponents producing higher or lower demands. Containing Japan required a much wider geographical perimeter than containing Italy. Older cruisers could provide convoy escort, while newer ships formed response forces. The broader 70-cruiser requirement also accounted for battle-fleet work and ships unavailable during routine maintenance. Trade protection was therefore one part of a fleet allocation built around geography, duties and availability.