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Plan Orange

Plan Orange was the U.S. Navy's contingency plan in the event of war with Japan. First developed following the First World War, when Japan was identified as the most likely naval opponent in a future war, the plan assumed that Japan would quickly seize control of most of the Philippines. The U.S. Navy would then launch a counteroffensive across the Mandates in the central Pacific with the goal of relieving Manila and blockading Japan. The plan was continually updated to reflect shifting alliances, improvements in naval technology, and the relative strengths of the fleets.

The Japanese correctly anticipated most of the features of Orange and prepared their own war plans accordingly. American planners, in turn, anticipated the Japanese response. Both sides assumed a numerical superiority of  3:2 in battleships in favor of the Americans, as established by the naval disarmament treaties. Under the square law of combat effectiveness, this all but guaranteed an American victory in the final decisive battle. The Japanese therefore put heavy emphasis on attrition tactics (zengen sakusen) to weaken the American battle line during its long voyage across the Pacific. These were based on night torpedo attack by destroyers and cruisers, and, as they became more capable, aircraft. The Americans in turn emphasized the use of destroyer flotillas to screen the battle line from light forces and aircraft. The American destroyers built to replace the "flush-deckers" were given adequate gun firepower and the guns were dual-use types with considerable antiaircraft capability.

Japanese submarine strategy was largely shaped by the imperatives of defending against Plan Orange. Japanese submarines were built with relatively high surface speed, typically 23 knots, in the belief that this would be sufficient to allow Japanese submarines to repeatedly sweep around and achieve firing position on an American force advancing at economical cruising speed. However, fleet exercises showed that the speed advantage was simply not sufficient and a submarine would get just one chance to attack any American force it made contact with. This constituted a serious flaw in the Japanese attrition strategy.

As late as 1938, Plan Orange assumed that the United States would be fighting without allies. The deteriorating international situation forced planners to reevaluate this assumption, and by 1941, Plan Orange was subsumed into the Rainbow series of war plans. These included several different cases, depending on whether the U.S. was allied with Britain or at war with Germany. The advance across the Pacific was expected to take up to two years, and the Philippines garrison was essentially written off. However, MacArthur managed to persuade the Roosevelt administration that the Philippines could be successfully defended with the help of a force of B-17 Flying Fortresses, an aircraft whose capabilities were grossly overestimated at the time. When MacArthur's air power was destroyed at the outset of war, MacArthur was forced to fall back on Plan Orange, which called for his forces to retreat into the Bataan Peninsula and hold out as long as possible.

Plan Orange failed to anticipate several important facets of the war, including the ascendancy of the aircraft carrier, the campaign in the jungles of the South Pacific, and the kamikazes. However, the central Pacific campaign of 1943-1944 and the approach to Japan in 1944-1945 followed the basic outline of Orange.

References

Friedman (2004)

Huston (1966)

Marston (2002)

Miller (1991)

Zimm (2011)



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