War Plan Orange

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War Plan Orange (commonly known as Plan Orange or just Orange) was the US Navy war plan for dealing with a possible Japanese attack in the interwar years. Predating the Rainbow plans, which presumed allies, Orange was predicated on the U.S. fighting Japan alone. It anticipated a withholding of supplies from the Philippine Islands and other U.S. outposts in the Western Pacific (they were expected to hold out on their own), while the Pacific Fleet marshaled its strength at bases in California, and guarded against attacks on the Panama Canal. After mobilization (the ships maintained only half of their crews in peacetime), the fleet would sail to the Western Pacific to relieve American forces in Guam and the Philippine Islands. Afterwards, the fleet would sail due north for a decisive battle against the Imperial Japanese Navy, and then blockade the Japanese home islands.

The Imperial Japanese Navy developed a counter-plan to allow the Pacific Fleet to sail across the Pacific while using submarines to weaken it. The Japanese fleet would then attempt to force a battle against the U.S. in a "decisive battle area", near Japan, after inflicting such attrition. This is in keeping with the theory of Alfred T. Mahan, a doctrine to which every major navy subscribed before World War Two, in which wars would be decided by engagements between opposing surface fleets^[1] (as they had been for over 300 years). It was the basis for Japan's demand for a 70% ratio (10:10:7) at the Washington Naval Conference, which would give Japan superiority in the "decisive battle area", and the U.S.'s insistence on a 60% ratio, which meant parity.^[2]

The American war planners failed to appreciate that technological advances in submarines and naval aviation had made Mahan's doctrine obsolete. In particular, the American planners did not understand that aircraft could sink battleships, nor that Japan would put the US battleship force (the Battle Line) out of action in an single attack -- as it did in the Battle of Pearl Harbor.

American plans changed after the Pearl Harbor attack, which demonstrated the supremacy of aircraft in naval warfare. Even after major Japanese defeats like Midway, the US fleet favored a methodical "island-hopping" advance, never going far beyond land-based air cover.^[3]

Moreover, by their obsession with "decisive battle", IJN would ignore the vital role of antisubmarine warfare.^[4] Germany and the U.S. would demonstrate the need for this with their submarine campaigns against Allied and Japanese merchant shipping respectively. The American campaign ultimately choked Japan's industrial production.

[edit] Notes

^ Mahan, Alfred T. Influence of Seapower on History, 1660-1783. Boston: Little, Brown.
^ Miller, Edward S. War Plan Orange. Annapolis, MD: United States Naval Institute Press, 1991.
^ Willmott, H.P. Barrier and the Javelin. Annapolis, MD: United States Naval Institute Press, 1983.
^ Parillo, Mark. Japanese Merchant Marine in World War 2. Annapolis, MD: United States Naval Institute Press, 1993.