Mexican Instability, War Plan Green, and the U.S. Army, 1903 - 1940

This thesis examines the U.S. Army?s GREEN series of war plans from the establishment of the Army General Staff in 1903 until the final update of the plan in 1940. It focuses on the evolution of the plans from their inception until they were declared obsolete. The content of the plans is analyzed in the context of U.S. relations with Mexico and the evolution of the General Staff and U.S. Army war planning.

At present, no comprehensive examination of the U.S. Army?s war plans for Mexico exists. Examinations of the U.S. Army?s interaction with Mexico focus almost entirely on the Mexican-American War and the two interventions in 1914 and 1916. This thesis represents the first examination of how the U.S. planned for military interventions in Mexico.

The central area of research of this thesis is the U.S. Army?s strategic plans. Each of the editions and revisions of the plan are described and assessed to identify strengths and weaknesses. The plans are analyzed as a series to identify patterns and trends. This examination determined that, while the plans were feasible, they were often disconnected from political reality, and sometimes had significant omissions, most notably in the area of occupation.

This thesis is based on primary sources, including the War Department?s strategic plans, records of the War College and War Plans Divisions, and Joint Board records. Secondary sources are used to place War Plan GREEN in the context of U.S.-Mexico relations and the development of the Army General Staff and Army war plans and war planning.