War Plan Orange

War Plan Orange (commonly known as Plan Orange or just Orange) refers to a series of United States Joint Army and Navy Board war plans for dealing with a possible war with Japan during the years between the First and Second World Wars.

Informal studies as early as 1906 covered a number of possibilities, from basing at Gibraltar or Singapore (an idea revived by the British before World War II) to "a quick trans-Atlantic dash" to the Pacific. The plan eventually adopted was conceived by Rear Admiral Raymond P. Rodgers in 1911.

The plan was formally adopted by the Joint Army and Navy Board beginning in 1924. Predating the Rainbow plans, which presumed the assistance of allies, Orange was predicated on the United States fighting Japan alone.

As originally conceived, it anticipated a blockade of the Philippines 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 Philippines. Afterwards, the fleet would sail North for a decisive battle against the Imperial Japanese Navy's Combined Fleet, and then blockade the Japanese home islands. This was in keeping with the theory of Alfred Thayer Mahan, a doctrine to which every major navy subscribed before World War II, in which wars would be decided by engagements between opposing surface fleets (as they had been for over 300 years).

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