What was War Plan Orange?


War Plan Orange (commonly known as Plan Orange or just Orange) is 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 (refer to US Colour-Coded War Plans).

It failed to foresee the significance of the technological changes to naval warfare including the submarine, air support and aircraft carriers, and although the Battle of Midway was important, and the US Navy did “island-hop” to regain lost territory, there was no culminating “showdown” battle as anticipated by Plan Orange.


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.

  • 19 Dec 1919 – Strategy of the Pacific (JB 325, Serial 28).
  • 7 Jul 1923 – Estimate of the Situation, Orange (JB 325, Serial 207).
  • 15 Aug 1924 – Joint Basic War Plan – Orange (JB 325, Serial 228).
  • 10 Jan 1929 – Revision of Joint Army and Navy Basic War Plan Orange (JB 325, Serial 280).
  • 20 Jun 1934 – Inadequacy of Present Military and Naval Forces Philippine Area to Carry Out Assigned Missions in Event of an ORANGE War (JB 325, Serial 533).
  • 8 May 1935 – Revision of Joint Army and Navy Basic War Plan – Orange (JB 325, Serial 546).
  • 19 May 1935 – Revision of Joint Army and Navy Basic War Plan – Orange (JB 325, Serial 570).
  • 14 Oct 1936 – Revision of Joint Orange Estimate of the Situation (JB 325, Serial 589).
  • 9 Dec 1936 – Changes in Joint Basic War Plan Orange (JB 325, Serial 594).
  • 19 Feb 1938 – Joint Army and Navy Basic War Plan Orange (1938) (JB 325, Serials 617 & 618).

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 assumed that the United States would fight Japan alone.


As originally conceived, it anticipated a blockade of the Philippines and other US 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 Hawaii, 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.

That 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).

The strategy followed by the US in the Pacific War differed little from Rodgers’ concept from 1911: a “leapfrog” campaign to conquer the Marshalls and Carolines (held by Japan before the war); liberation of the Philippines; and blockade. Absent was the “decisive battle” of Mahan, and of Japanese planning.

Japanese Plans

The Imperial Japanese Navy developed a counter-plan to allow the US Pacific Fleet to sail across the Pacific while using submarines and carrier attacks to weaken it. The Japanese fleet would then attempt to force a fleet action against the weakened US fleet in a “decisive battle area”, near Japan (see Kantai Kessen), also in line with Mahanian doctrine, which Japan had enthusiastically embraced. It was the basis for Japan’s demand for a 70% ratio (10:10:7) at the Washington Naval Conference, which was considered necessary to provide Japan superiority in the “decisive battle area” (taking into account that the US had naval commitments in other theatres, while Japan did not). It was also the basis of the United States’ insistence on 60%, which amounted to parity.


Actual events generally followed the plan. Although carrier battles and the use of airplanes and submarines overshadowed surface action, the “leapfrog” campaign played out largely as anticipated.

The Imperial Japanese Navy, obsessed with the “decisive battle” doctrine, ignored the vital need for defence against submarines. The German and American submarine campaigns against their opponents’ merchant shipping demonstrated the need for an anti-submarine warfare strategy. While the Allies took extensive measures to combat the threat of German U-boats, the Japanese failed to effectively counter the American submarines which ultimately choked Japan’s industrial production and paralyxed her navy. Japan also notably failed to institute an anti-commerce campaign herself; systematic use of commerce raiders could have made Allied operations much more complex and conquering and holding Japanese-held islands more difficult.

American war planners failed to appreciate that technological advances in submarines and naval aviation had made Mahan’s doctrine obsolete and did not anticipate a pre-emptive strike from the Japanese. In particular, they did not yet know either that aircraft would be able to effectively sink battleships or that Japan might put the American battleship force (the Battle Line) out of action at a stroke, which actually happened at Pearl Harbour on 07 December 1941.

American plans changed after this attack. Even after major Japanese defeats like Midway, once the effectiveness of aircraft carriers was known, the Americans favoured a methodical “island-hopping” advance, never going far beyond land-based air cover. Meanwhile, a blockade was imposed from the very beginning of the war, with the first American submarine, USS Gudgeon, arriving off Japan on about 31 December 1941.

A number of requirements grew out of Orange, including the specification for a fleet submarine with high speed, long range, and heavy torpedo armament. These coalesced in the submarine Dolphin in 1932 (only to be rejected and returned to with the Gato class in around August 1941). The demand for submarines of this size also drove the development of the notoriously problematical Mark 14 torpedo (and its equally notorious Mark VI exploder), under the guidance of Commander Ralph W. Christie. The Navy also spent “several hundred thousand dollars” to develop powerful, compact diesel engines, among them the troublesome Hooven-Owens-Rentschler (HOR), which proved useful for railroads.


Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.