2-073 Editorial Note on U.S. War Plans, April-November 1939

Publisher: The Johns Hopkins University Press

Editorial Note on U.S. War Plans

April-November 1939

Contingent plans for operations against Japan had been made by the summer of 1924, when the Joint Board issued Joint War Plan Orange. The plan emphasized an offensive naval war in the Pacific with the Philippines as the main base. From Manila Bay the United States would establish itself in the western Pacific “in strength superior to that of Japan.” But by the mid-1930s, Japan’s growing power had forced the planners to conclude that that nation could be defeated only by a long and costly war. The Philippines would probably be lost early in such a conflict, and the United States would have to reduce Japan’s bases one at a time, beginning with those in the Marshall and Caroline islands. (Louis Morton, Strategy and Command: The First Two Years, a volume in the United States Army in World War II [Washington: GPO, 1962], pp. 28-30; Maurice Matloff and Edwin M. Snell, Strategic Planning for Coalition Warfare, 1941-1942, a volume in the United States Army in World War II [Washington: GPO, 1953], p. 2.)

Revisions of Plan Orange, however, continued to emphasize Manila Bay as the main outlying base of operations. In the late 1930s, changing world political conditions forced United States planners to reevaluate their strategic assumptions and to plan for coalition warfare. After enumerating possible contingencies, the Joint Board in April 1939 called for a series of war plans, each applicable to a different situation. As the various nations were designated by colors in the army-navy plans, coalitions naturally suggested a rainbow. Rainbow 1 was basic and preliminary to the execution of the other four plans; it provided for the defense of the Western Hemisphere north of 10

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