Why convoy protection consumes entire fleets

Convoys reduce the number of formations that need protection, but only work when escorts are available at the right places. In World War I the Royal Navy had hundreds of destroyers and sloops yet still faced simultaneous demands from the Grand Fleet, Harwich Force, Channel defences, patrols, and merchant routes. Every concentration of escorts created a weaker area that submarines could seek out, making some risk unavoidable unless the fleet acquired still more ships. American four-stack destroyers based at Queenstown divided the burden by taking responsibility for the southern Irish approaches while British forces concentrated farther north. Entrusting a major approach route to another navy demonstrated the operational necessity and Allied trust behind this division of responsibility.