War Plan Rainbow

War Plan Rainbow War Plan Rainbow was a series of United States contingency plans prepared during the interwar period to address potential conflicts involving multiple adversaries in the Atlantic and Pacific theaters. Conceived and revised by staff of the United States Department of War, War Department General Staff, United States Army War College, and United States Navy planners, the Rainbow papers intersected with policy debates involving the United Kingdom, France, Soviet Union, Imperial Japan, and other powers. The plans were shaped by lessons from the First World War, developments in the Washington Naval Conference, and evolving doctrine at the Army Air Corps and United States Fleet.

Background and development

The genesis of Rainbow planning grew from earlier American contingency efforts including the interwar series such as the Plan Orange and Plan Black, influenced by analyses from the General Staff, Chief of Staff of the United States Army, and the Chief of Naval Operations. Planners drew on operational studies produced at the Naval War College, Army War College, and Office of Naval Intelligence, and incorporated strategic assumptions debated at the International Military Tribunal for the Far East and policy fora like the Washington Naval Treaty and London Naval Treaty. The climate of the 1920s and 1930s—marked by the Great Depression, the rise of Fascist Italy, Nazi Germany, and Imperial Japan—prompted staff officers from the War Department General Staff and Navy War Plans Division to craft contingencies that anticipated coalitions involving the United Kingdom, France, China, Soviet Union, and regional powers such as Germany, Italy, and Japan. Key contributors included officers from the General Staff College, the Army Signal Corps, the Bureau of Aeronautics, and analysts from the Office of Strategic Services precursor organizations.

Strategic objectives and scenarios

Rainbow planning enumerated strategic objectives tied to a range of opponent combinations: defending the Panama Canal against hostile sea power, protecting the Philippine Islands, and supporting allies in the North Atlantic and Mediterranean Sea. Scenarios ranged from unilateral conflicts with Imperial Japan to global wars involving the United Kingdom and France against Nazi Germany and its partners, or simultaneous threats from Germany in Europe and Japan in the Pacific. The planners considered operational requirements such as convoy escorting in the Atlantic Ocean, island defense across the Philippine Sea, interdiction of Axis sea lines of communication, and cooperation with allied naval forces including the Royal Navy and French Navy. Strategic documents referenced global chokepoints like the Suez Canal, Strait of Gibraltar, and Malacca Strait, and envisaged coordination with expeditionary forces modeled after American Expeditionary Forces concepts and joint operations similar to later efforts at Normandy and in the Solomon Islands.

Implementation and operational planning

Operational planning for Rainbow emphasized mobilization, force projection, and phased deployment of the United States Atlantic Fleet and United States Pacific Fleet. Staffs produced order-of-battle assessments, logistic plans leveraging bases at Guam, Pearl Harbor, Panama Canal Zone, and Guantanamo Bay, and tailored air support concepts involving the Army Air Corps and United States Marine Corps aviation units. Planners integrated lessons from expeditionary operations like the Gallipoli Campaign and amphibious doctrine experiments at the Naval Amphibious Base Coronado, anticipating requirements for Amphibious Corps assaults, carrier task force operations modeled on concepts by Admiral Ernest King and Admiral Husband E. Kimmel, and anti-submarine warfare informed by tactics used against U-boat campaigns during the Battle of the Atlantic. Training programs at Fort Bragg, Fort Leavenworth, and naval yards at Norfolk Navy Yard adapted to Rainbow priorities, while procurement decisions at Bethlehem Steel, Puget Sound Naval Shipyard, and aviation industries such as Boeing and Lockheed reflected anticipated materiel needs.

Intelligence, diplomacy, and interwar context

Rainbow planners relied on intelligence estimates from the Office of Naval Intelligence, the Army G-2, and diplomatic reporting from the Department of State, American embassies in Tokyo, Berlin, London, and Paris, and station reports from Consulates in Shanghai and Manila. The plans were shaped by treaties and diplomatic frameworks including the Washington Naval Conference, the Nine-Power Treaty, and shifting relations with the Soviet Union after the Russian Revolution and the diplomatic recognition debates of the 1930s. Interactions with allied staffs—especially liaison with the British Admiralty and the French General Staff—influenced assumptions about coalition logistics, fleet dispositions, and diplomatic coordination in crises such as the Second Sino-Japanese War and the Spanish Civil War. Intelligence failures and analytic debates involving cryptanalysis efforts, signals intelligence theaters like Bletchley Park and early American efforts foreshadowing the Magic program informed assessments of enemy intentions and timing.

Criticism, assessments, and legacy

Historical assessments of Rainbow highlight strengths in contingency thinking but criticize rigidity in assumptions and the challenge of translating staff plans into real-time strategy. Scholars compare Rainbow with other interwar plans like Plan Black and Plan Orange, and note how Rainbow influenced wartime directives such as War Plan ORANGE implementation and directives by President Franklin D. Roosevelt and Joint Chiefs of Staff decisions during World War II. Critics point to coordination issues among the War Department and Navy Department, intelligence uncertainties involving Ultra and Magic, and logistical shortfalls revealed in campaigns such as Philippine campaign (1941–42) and early Battle of the Coral Sea operations. Legacy threads link Rainbow to postwar planning evolutions at the National Security Council, the creation of the Department of Defense, and doctrinal development at the United States Strategic Command and NATO strategic planning cells, while historians at institutions like the United States Army Center of Military History and universities including Harvard University and United States Naval Academy continue to analyze its impact.

Category:United States military planning