“Drafting conscript workers was one thing. But unless they were adequately fed they were useless. There was no industry in the 1940s in which the correlation between labour productivity and calorific input was more direct than in mining.91 But after 1939 the food supply in Western Europe was no less constrained than the supply of coal.92 As was true of Germany, the high-intensity dairy farms of France, the Netherlands and Denmark were dependent on imported animal feed. Grain imports in the late 1930s had run at the rate of more than 7 million tons per annum mostly from Argentina and Canada. These sources of supply were closed off by the British blockade. In addition Western Europe had imported more than 700,000 tons of oil seed.93 Of course, France was a major producer of grain in its own right. But French grain yields depended, as they did in Germany, on large quantities of nitrogen-based fertilizer, which could be supplied only at the expense of the production of explosives. And like German agriculture, the farms of Western Europe depended on huge herds of draught animals and on the daily labour of millions of farm workers. The removal of horses, manpower, fertilizer and animal feed that followed the outbreak of war set off a disastrous chain reaction in the delicate ecology of European peasant farming. By the summer of 1940, Germany was facing a Europe-wide agricultural crisis.”