How the Admiralty turned trade routes into cruiser requirements

The Admiralty treated trade protection as its largest ongoing staff project, maintaining a continuing study of merchant traffic. It ran from the First Sea Lord's office with the Third Sea Lord involved and, at times, the Fourth Sea Lord. It considered typical merchant ship size, the volume and economic value of traffic, and what protection each route already had. A planning total had to cover both trade and the cruisers needed with the fleet. The Japan example gives roughly 70 cruisers, and the same approach informed estimates for Germany and Italy. A proposed combined study for all three opponents went unauthorised, with the likely size of the resulting requirement a concern.