U.S. Color-coded War Plans

During the 1920s, the United States Army developed a number of Color-coded War Plans to outline potential U.S. strategies for a variety of hypothetical war scenarios. All of these plans were officially withdrawn in 1939, in favor of five Rainbow Plans developed to meet the threat of a two ocean war against multiple Axis Powers.

The best-known of these plans (although they were secret at the time) is probably War Plan Orange, a plan for war with Japan, which formed some of the basis for the actual campaign against Japan in World War II.

War Plan Red, a more hypothetical plan for war against Britain and Canada, caused a stir in American-Canadian relations when declassified in 1974. A related plan was War Plan Crimson, which envisioned a limited war with the British Empire concentrating on an invasion of Canada. In this color scheme, the UK was "Red," Canada "Crimson," and Australia/New Zealand were "Scarlet."

There were other color-coded plans developed during this period:

• War Plan White dealt with a domestic uprising in the US, and later evolved to Operation Garden Plot, the general US military plan for civil disturbances. Parts of War Plan White were used to deal with the Bonus Expeditionary Force in 1932.

• War Plan Gray dealt with invading a Caribbean republic

• War Plan Purple dealt with invading a Central American republic, or with Russia (There may have been two different Purples).

• War Plan Green involved invading Mexico and occupying Mexico City to establish a pro-American government.

• War Plan Gold with France and French caribbean posessions.

• War Plan Black with Germany. The best-known version of Black was conceived as a contingency plan during World War I in case France fell and the Germans attempted to seize French possessions in the Caribbean.

• War Plan Indigo involved an invasion of Iceland. In 1941, while Denmark was under German occupation, the US did occupy Iceland, relieving British units during the Battle of the Atlantic.

• War Plan Brown - an uprising in the Philippines.

• War Plan Yellow - war in China - specifically, the defense of Peking and relief of Shanghai, during the Sino-Japanese War.

In addition there were combinations such as Red-Orange, which was necessitated by the Anglo-Japanese military alliance which expired in 1924.

Many of the war plans are extremely hypothetical considering the state of international relations in the 1920s. Often, junior officers were given the task of updating the plans to keep them busy. Interestingly, although the U.S. had fought its most recent war against Germany and would fight another within a few years, when it emerged that the Army was constructing a plan for a war with Germany, intense domestic pressure emerged for the Army to halt planning, because isolationists opposed any consideration of involvement in a future European war. This may have encouraged the Army to focus on more speculative scenarios for planning.

Several of these plans were likely to be put into effect. Japan had used the opportunity afforded by World War I to establish itself as a major power and the US's main strategic rival, especially in the Pacific Ocean. Following World War I, most American officials and planners considered a war with Japan to be highly likely. It was reverted when the civilian government temporarily halted the program of military expansion, which was not to resume until 1931. Notably, Orange is the longest and most-detailed of the plans, and many of its elements were carried over into Plan Rainbow Five, the current plan at the time of Pearl Harbor.

During the 1910s the US had invaded Mexico in search of Pancho Villa, whose rebel band had attacked a New Mexico town; earlier, US forces had seized the port of Veracruz, Veracruz, and forced dictator Victoriano Huerta to resign. Relations with Mexico remained tense into the 1920s and 1930s.

Between the United States Civil War and World War I, the American military frequently intervened in the affairs of Latin American countries. This policy continued during the 1920s and 1930s, and "Gray" and "Purple," although never officially activated, were used.