Japan took the opportunity afforded by World War I to establish itself as a major strategic power in the Pacific Ocean. Most American officials and planners then considered a war with Japan to be highly likely. The fear lessened when the civilian government of Japan temporarily halted its program of military expansion, but it was resumed in 1931. War Plan Orange was the longest and most detailed of the color-designated plans. However, following the
Second Sino-Japanese War in 1937 and events in Europe in 1938—1940 (the
Anschluss, the
Munich Agreement, the
German occupation of Czechoslovakia, the
Molotov–Ribbentrop Pact and the German
invasion of Poland and
Western Europe), American war planners realized that the United States faced war on multiple fronts against a coalition of enemies. Therefore, the Joint Planning Board developed a new series of "Rainbow" plans—the term being a logical extension of the previous "color" plans. • Rainbow 1 was a plan for a defensive war to protect the United States and the Western Hemisphere north of 10th parallel south|ten degrees [south] latitude. In such a war, the United States was assumed to be without major allies. • Rainbow 2 was identical to Rainbow 1, except for assuming that the United States would be allied with France and the United Kingdom. • Rainbow 3 was a repetition of the Orange plan, with the provision that the hemisphere defense would first be secured, as provided in Rainbow 1. • Rainbow 4 was based on the same assumptions as Rainbow 1 but extended the American mission to include defense of the entire Western hemisphere. •
Rainbow 5, destined to be the basis for American strategy in World War II, assumed that the United States was allied with Britain and France and additionally provided for offensive operations by American forces in Europe, Africa, or both. The assumptions and plans for Rainbow 5 were discussed extensively in the
Plan Dog memo, which concluded ultimately that the United States would adhere to a
Europe first strategy in World War II. The publication ignited a storm of controversy in the US, with isolationist politicians claiming Roosevelt was violating his pledge to keep the country out of the European war, while Secretary of War
Henry L. Stimson accused the newspapers of unpatriotic behavior and suggested it would be a dereliction of duty for the War Department not to plan for every contingency. Germany publicly ridiculed the plan the next day, doubting "whether the entire world shipping would be sufficient to transport 5,000,000 troops to Europe, much less supply them there." Privately, the German general staff saw the publication of the plans as extremely valuable intelligence and used its threat of a five-million-man US force in 1943 to argue for temporarily stalling the faltering
invasion of the Soviet Union, and concentrating German forces in the west.
Adolf Hitler vehemently rejected that idea. Historian Thomas Fleming suggests that Germany might have prevailed against the UK and the US if he had not. The source of the leak was determined in 1962 in an autobiography by former Senator Burton Wheeler (D-Montana) when he stated that it was he who leaked the secret defense plans to the press. == See also ==