It ruled a quarter of the world’s land surface; its navy controlled the most critical sea lanes.
Yet the resources on which its population depended to live and its armed forces depended to fight came from distant colonies and, increasingly, the U.S.
The fleet that carried these supplies was highly vulnerable to German U-boats.
WSJ 7 January 2022
Britain's War: Into Battle, 1937-1941
By Daniel Todman (2016)