During the 1920s and 1930s, the United States Armed Forces developed a number of color-coded war plans that outlined potential US 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 The plans, developed by the Joint Planning Committee (which later became the Joint Chiefs of Staff), were officially withdrawn in 1939 at the outbreak of World War II in favor of five "Rainbow" plans developed to meet the threat of a two-ocean war against multiple enemies.
A military operation plan (commonly called a war plan before World War II) is a formal plan for military armed forces, their military organizations and units to conduct operations, as drawn up by commanders within the combat operations process in achieving objectives before or during a conflict. Military plans are generally produced in accordance with the military doctrine of the troops involved. Because planning is a valuable exercise for senior military staff, in peacetime nations generally produce plans (of varying detail) even for very unlikely hypothetical scenarios.
Plan XVII and the Schlieffen Plan are examples of World War I military plans. The United States developed a famous color-coded set of war plans in the early 20th century; see United States color-coded war plans.