This article needs a complete rewrite for the reasons listed on the talk page. Please remove this notice once this has been done.
The article related to this talk page is geographically limited: the general perspective and/or specific examples represent a limited number of countries. If you can give a more global perspective to this article then please consider editing (http://en.wikipedia.org/w/index.php?title=War_plan&action=edit) it and sharing your knowledge. Please see the countering systemic bias project page for more general information.
Generally speaking, war plans are simply preprepared plans for military action against likely opponents. The United States developed a famous color-coded set of war plans in the early part of the 20th Century. Each color referred to a different opponent, often based on the color of their flag.
The colored war plans included:
War Plan Black - 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.
War Plan Gray - naval war against Caribbean nations.
War Plan Green - war with Mexico.
War Plan Gold - war with France.
War Plan Red - war with the United Kingdom. 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."
War Plan Red-Orange - war against both the UK and Japan (which had an alliance for some time before World War II).
War Plan Purple - war with Russia, or a Latin American nation. (There may have been two different Purples.)
War Plan Yellow - war in China - specifically, the defense of Peking and relief of Shanghai, during the Sino-Japanese War.
War Plan White - domestic uprising. White eveolved into Operation Garden Plot, the generic US military plan for civil disturbances.
By 1939, the remnants of Orange and Black were folded into a copmpletely new set of plans called "Rainbow," which covered American conflict with Italy, Germany, and Japan, possibly in coordination with Britain and France.
While many of these plans were kept updated through the 1930s, not every scenario was equally likely. For instance, though war with Britain and Canada was a faint possibility at the beginning of WWI, it was extremely unlikely by the last revision of Crimson in the mid-30s. (Often, junior officers were given the task of updating the plans to keep them busy.) On the other hand, Orange actually formed the basis of the American strategy in the South Pacific theater of WWII.
The chief aim of Plan XVII, devised by Ferdinand Foch in the wake of the humiliation of the Franco-Prussian War, and taken up by French Commander-in-Chief Joseph Joffre in 1913, was the recapture of the territory of Alsace and Lorraine.
Plan R (for Russia) essentially revised Plan B, allowing for a greater volume of troops to guard against Russian assistance for the Serbs in the south, whilst assuming German activity in the north.
Instead, upon the declaration of war (or, in the case of Germany, invasion), the entirety of Belgium's armed forces, comprising 117,000 field troops, were concentrated west of the River Meuse in the (ultimately unsuccessful) defence of Antwerp.