Plan Dog

The Plan Dog memorandum was a 1940 American government document written by Chief of Naval Operations Harold Rainsford Stark, and has been called "one of the best known documents of World War II". Confronting the problem of an expected two-front war against Germany and Italy in Europe and Japan in the Pacific, the memo set out the main options and suggested fighting a defensive war in the Pacific while giving strategic priority to defeating Germany and Italy. The memo laid the basis for the later American policy of Europe first.

During the Interwar period, the Joint Planning Committee (which later became the Joint Chiefs of Staff) devised a series of contingency plans for dealing with the outbreak of war with various countries. The most elaborate of these, War Plan Orange, dealt with the possibility of war with Japan.

In light of the events of the late 1930s (the outbreak of the Second Sino-Japanese War, the Molotov-Ribbentrop Pact, the German conquest of Poland and Western Europe) American planners realized that the United States faced the possibility of a two-front war in both Europe and the Pacific. War Plan Orange was withdrawn, and five "Rainbow" plans were put forward. Unlike the earlier colored plans which had assumed a one-on-one war, the Rainbow plans contemplated possibility of fighting multiple enemies, and the necessity of defending other western hemisphere nations and aiding Britain.

The memorandum built upon the conditions described in the Rainbow Five war plan. It described four possible scenarios for American participation in World War II, lettered A through E:

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