This was the question posed by Sir John Simon, the Chancellor of the Exchequer, as British rearmament policy took priority over normal trade in 1939. This development was long before the crisis of 1940 or the appearance of Lend-Lease in 1941, and indicates how concepts of the economic limitations on British military power stretch back into the pre-war period. The conundrum posed by Simon could be resolved only by national economic mobilisation on a scale beyond the Chamberlain government's initial preferences and eventually by plans for American aid on an enormous scale.

During the rearmament period between 1938 and 1940, British policy would have to grapple with this problem without American aid. Between 1932 and 1939 the strategic alignment of British defence policy changed dramatically. In 1932 Britain remained ostensibly wedded to the ‘Ten-Year Rule’, the assumption that no war with a major power could be expected in the next ten years, and military planning and expenditure were limited as a result.