The German plan for conquering Poland, Case White, provided the scenario for what ensued. They had many such plans, like Case Green, the invasion of Czechoslovakia (which they never had to use), and Case Yellow, the attack on France. Color-coded master plans for smashing other countries, far in advance of any quarrel with them, were a modern military innovation of the Germans. All advanced nations came to imitate this doctrine. The United States, for instance, by 1939 had a Plan Orange for fighting Japan, and even a Plan Red for fighting England; and it finally entered the war under Plan
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