United States color-coded war plans

During the 1920s and 1930s, the United States military Joint Army and Navy Board developed a number of color-coded war plans to outline potential U.S. strategies for a variety of hypothetical war scenarios. The plans, developed by the Joint Planning Committee (which later became the Joint Chiefs of Staff), were officially withdrawn in 1939 in favor of five Rainbow Plans developed to meet the threat of a two-ocean war against multiple enemies.

Colors
The use of colors for U.S. war planning originated from the desire for the Army and Navy to use the same symbols for their plans. At the end of 1904, the Joint Board adopted a system of colors, symbols, and abbreviated names to represent countries. Many war plans became known by the color of the country to which they were related, a convention that lasted through World War II. As the convention of using colors took root, some were eventually reused, such as Grey, which originally referred to Italy but eventually became a plan for the capture and occupation of the Azores.

In all the plans the U.S. referred to itself as "Blue".

The plan that received the most consideration was War Plan Orange, a series of contingency plans for fighting a war with Japan alone, outlined unofficially in 1919 and officially in 1924. Orange formed some of the basis for the actual campaign against Japan in World War II and included the huge economic blockade from mainland China and the plans for interning the Japanese-American population of Hawaii.

War Plan Red was a plan for war against Britain and Canada. British territories had war plans of different shades of red—the UK was "Red", Canada "Crimson", India "Ruby", Australia "Scarlet" and New Zealand "Garnet". Ireland, at the time a free state within the British Empire, was named "Emerald". The plan was kept updated as late as the 1930s and caused a stir in American–Canadian relations when declassified in 1974.

War Plan Black was a plan for war 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 or launch an attack on the eastern seaboard.

Considerations
Many of the war plans were extremely unlikely given the state of international relations in the 1920s, and were entirely in keeping with the military planning of other nation-states. Often, junior military officers were given the task of updating each plan to keep them trained and busy (especially in the case of War Plan Crimson, the invasion of Canada). Some of the war plan colors were revised over time, possibly resulting in confusion.

Interestingly, although the US had fought its most recent war against Germany and would fight another within twenty years, intense domestic pressure emerged for the Army to halt when it became known that the Army was constructing a plan for a war with Germany; isolationists opposed any consideration of involvement in a future European conflict. This may have encouraged the Army to focus on more speculative scenarios for planning exercises.

War Plan Green
During the 1910s, relations between Mexico and the United States were often volatile. In 1912, U.S. President William Howard Taft considered sending an expeditionary force to protect foreign-owned property from damage during the Mexican Revolution. Thus War Plan Green was developed. In 1916, U.S. troops under General John Pershing invaded Mexico in search of Pancho Villa, whose army had attacked Columbus, New Mexico; earlier, American naval forces had bombarded and seized the Mexican port of Veracruz, and forced Victoriano Huerta to resign the residence. In 1917, British intelligence intercepted a telegram from the German foreign ministry to its embassy in Mexico City offering an alliance against the United States and assistance in the Mexican reconquest of the Southwest. Released to American newspapers, the Zimmermann Telegram helped turn American opinion against Germany and further poisoned the atmosphere between the USA and Mexico. Relations with Mexico remained tense into the 1920s and 1930s.

Beyond Mexico
Additionally, between the United States Civil War and World War I, the American military frequently intervened in the affairs of Latin American countries, including Colombia/Panama, Haiti, Cuba, and Nicaragua. This policy continued during the 1920s and 1930s, and parts of "Gray" and "Purple", although never officially activated, were used.

Multilateral war plans
Some plans were expanded to include war against a coalition of hostile powers.

The most detailed was Red-Orange, based on a two-front war against the Anglo-Japanese Alliance, which expired in 1924. This was the contingency which most worried U.S. war planners, since it entailed a two-ocean war against major naval powers. Theories developed in wargaming Red-Orange were useful during World War II, when the United States engaged the Axis in both the Atlantic and Pacific simultaneously.

Rainbow plans
Japan had used the opportunity afforded by World War I to establish itself as a major power and a strategic rival 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. War Plan Orange was the longest and most-detailed of the colored plans.

However, following the events in Europe in 1938 and 1939 (the Anschluss, Munich Agreement, German occupation of Czechoslovakia, and Molotov–Ribbentrop Pact), American war planners realized that the United States faced the possibility of war on multiple fronts against a coalition of enemies. To that end, the Joint Planning Board developed a new series of war plans, the "Rainbow" plans - the term being a play on the multiple "color" plans that had been drawn up previously.


 * Rainbow 1 was a plan for a defensive war to protect the United States and the Western Hemisphere north of ten degrees [south] latitude. In such a war, the United States was assumed to be without major allies.
 * Rainbow 2 assumed that the United States would be allied with France and Britain.
 * Rainbow 3 was a repetition of the Orange plan, with the proviso that the hemisphere defense would first be secured, as provided in Rainbow 1.
 * Rainbow 4 was based on the same assumptions as Rainbow 1, but extended the American mission to include defense of the entire Western hemisphere.
 * Rainbow 5, destined to be the basis for American strategy in World War II, assumed that the United States was allied with Britain and France and provided for offensive operations by American forces in Europe, Africa, or both.

The assumptions and plans for Rainbow 5 were discussed extensively in the Plan Dog memo, which concluded ultimately that the United States would adhere to a Europe first strategy in World War II.

List of Color Plans
According to the public intelligence site, Global Security, the following plans are known to have existed:


 * War Plan Black
 * A plan for war 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 Sea or launch an attack on the eastern seaboard.


 * War Plan Gray
 * There were two War Plans named Gray. The first dealt with Central America and the Caribbean, and the second dealt with invading the Portuguese Azores.
 * War Plan Brown
 * Dealt with an uprising in the Philippines.


 * War Plan Tan
 * Intervention in Cuba.


 * War Plan Red
 * Plan for Great Britain (with sub variants Crimson, Scarlet, Ruby, Garnet, and Emerald for British dominions)


 * War Plan Orange
 * Plan for Japan.


 * War Plan Red-Orange
 * Considered a two-front war with the United States (Blue) opposing Japan (Orange) and the British Empire (Red) simultaneously. Ultimately this analysis led to the understanding that the United States didn't have the resources to fight a two front war, and it would make sense to focus on one front, probably in the Atlantic. Ultimately this was the decision made in the Plan Dog memo.


 * War Plan Yellow
 * Dealt with war in China - specifically, the defense of Beijing and relief of Shanghai during the Second Sino-Japanese War.


 * War Plan Gold
 * Involved war with France, and/or France's Caribbean colonies.


 * War Plan Green
 * Involved war with Mexico or what was known as "Mexican Domestic Intervention" in order to defeat rebel forces and establish a pro-American government. War Plan Green was officially canceled in 1946.


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


 * War Plan Purple
 * Dealt with invading a South American republic.


 * War Plan Violet
 * Covered Latin America.


 * 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 and peaceful protests. Parts of War Plan White were used to deal with the Bonus Expeditionary Force in 1932. Communist insurgents were considered the most likely threat by the authors of War Plan White.


 * War Plan Blue
 * Covered defensive plans and preparations that the United States should take in times of peace.