"Machine-tools, ball-bearings, magnetos, internal combustion engines, drugs – it is hard to name a basic necessity of advanced technology in which Britain was self-sufficient in 1915... Thus the audit rendered by the first two years of the war on Britain's own capabilities in newer technologies proved harsh enough. Nonetheless, economic historians might object that Britain's Victorian and Edwardian "total strategy" actually served her well enough in wartime. Thanks to her accumulated wealth and her credit as the centre of a global free trade economy and thanks also to British seapower, she could buy in all the technological imports that she needed – largely from North America. But there are two snags here. First, wealth and credit are wasting assets when spent, while the spending only serves to profit other countries' manufacturers and build up their industries. In contrast, up-to-date export industries of your own are long-term earners. Secondly, the high degree to which free trade had rendered Britain dependent on imports of food and raw materials actually brought her near to complete national defeat in 1917 at the hands of the U-boat... Moreover, even though the U-boat was narrowly beaten, Britain had to devote immense naval resources to the merely defensive purpose of keeping open her sea lifelines. This pattern was to be repeated in the Second World War."