In the interwar period, the Joint Planning Board of the Army and Navy postulated a series of “color” plans outlining possible future enemies and scenarios in which the US might find itself at war. They were called color plans as the potential foe in each scenario was designated by a color.
While the likelihood of a war with Britain was low, prudence insisted that plans nonetheless be made. Mexico was similarly a low probability situation, but outline plans were drafted anyway. In all cases, these weren’t detailed operational plans, but rather synopsis of the strategic situation, outlining US interests, goals, and possible methods to achieve those goals, given the resources available or anticipated to be available.
In early 1939, with war clouds gathering on the horizon, for the first time, the Joint Planning Board began to examine the possibility that the US would face multiple enemies. As more than one color was involved, the “Rainbow” series of plans were drafted. After the Japanese attack at Pearl Harbor on December 7, 1941, the US found itself in a war that most closely resembled the scenario of “Rainbow 5.”
RAINBOW 5 assumed the United States, Great Britain, and France to be acting in concert; hemisphere defense was to be assured as in RAINBOW 1, with early projection of U.S. forces to the eastern Atlantic, and to either or both the African and European continents; offensive operations were to be conducted, in concert with British and allied forces, to effect the defeat of Germany and Italy. A strategic defensive was to be maintained in the Pacific until success against European Axis Powers permitted transfer of major forces to the Pacific for an offensive against Japan.
The amazing prescience of the Joint Planning board is not really evident until you realize that Rainbow 5 was written even before the war began. I don’t mean, before our entry in the war. I mean, before Germany even invaded Poland. Mind you, this was even before the US and Great Britain has established what came to be known as the Special Relationship.
Obviously, events of the war didn’t always follow the path forseen by Army and Navy planners. The plans weren’t intended to do that. They were intended to provide an intellectual framework upon which to build the actual strategies and then operations to fight the war.
One certainly wonders if today’s structure of the Joint Chiefs of Staff, as the principal military advisors to the President, and the National Security Council, the primary strategic planning arm of the government, are nearly as capable of providing such an accurate picture of likely future events, and the possible courses of action that would flow from them.