100th Infantry Division

100th Infantry Division
Unit name	100th Infantry Division
Dates	1918–1919; 1921–present
Country	United States
Branch	United States Army
Type	Infantry
Role	Training and readiness
Size	Division
Garrison	Fort Knox, Kentucky
Nickname	"Century Division"
Battles	World War I, World War II
Notable commanders	Ernest J. Dawley, John B. Anderson (general)

100th Infantry Division is a formation of the United States Army with service in both World Wars and continuing functions in the United States Army Reserve. Organized as an infantry division, the unit earned distinction in the Western Front (World War I), the European theatre of World War II, and subsequent Cold War and post–Cold War missions. The division transitioned from combat operations to training and support roles, aligning with broader force structure changes involving the Department of Defense and reserve component modernization.

Formation and World War I

Constituted in the National Army in 1918, the division drew personnel from the Midwest United States and trained at camps such as Camp Bowie and Camp Grant. During the late stages of the First World War, the division prepared for deployment to the Western Front (World War I) and became part of the American Expeditionary Forces under the command relationships set by John J. Pershing and staff elements from the American Expeditionary Forces (AEF). Elements arrived in the Western Front (World War I) theater as the Armistice approached, and the division performed occupation duties in the Rhineland and the demobilization process after the Armistice of 11 November 1918. Organizational patterns followed the triangular division structure then under discussion in the General Staff of the Army and reflected lessons from the Meuse-Argonne Offensive.

Interwar Period and Reconstitution

After demobilization, the division was reconstituted in the Organized Reserve in 1921 and headquartered in states across the Upper Midwest. During the interwar years, the division participated in Citizens’ Military Training Camps and maintained cadre strength in accordance with policies promulgated by the National Defense Act of 1920 and guidance from the War Department. Its officers attended professional education at institutions such as the United States Army Command and General Staff College and the United States Army War College, linking reserve readiness to active component doctrine. The division’s peacetime structure adapted to budgetary constraints of the Great Depression and to doctrinal debates influenced by proponents of mechanization like Adna R. Chaffee Jr..

World War II Operations

Ordered into active service in 1942, the division trained at posts including Camp Claiborne and deployed to the European theatre of World War II in late 1944. Assigned to operations in the Rhine campaign, the division engaged in offensive and defensive battles across the Moselle River sector and advanced through regions of Lorraine (department) toward the Saar Basin. The division participated in actions that intersected with units such as the Third Army (United States) and maneuvered in coordination with corps-level commands. It fought during the Battle of the Bulge period for control of key road networks and later advanced into Germany toward the Ruhr Pocket, affecting the collapse of organized resistance in western Germany. Division soldiers received individual and unit decorations tied to valorous actions within larger campaigns like the Allied advance from Paris to the Rhine.

Postwar Service and Cold War Activities

Following victory in Europe (1945), the division performed occupation duties in central Europe before inactivation during the postwar drawdown and reconstitution in the reserves. During the Cold War, the division’s Reserve elements supported mobilization planning for scenarios involving the North Atlantic Treaty Organization and integrated training with active component exercises under directives from Continental Army Command. The division adapted to force restructures such as the transition to the Total Force Policy era and participated in reserve mobilization tests, civil support operations, and cooperative training with National Guard units responding to domestic emergencies and international contingency plans.

Modern Role and Organizational Structure

In its contemporary role, the division operates primarily as a training and mobilization headquarters within the United States Army Reserve, overseeing brigade-level training, mobilization readiness, and support to Army transformation initiatives. The division’s structure includes multiple subordinate brigades and battalions focused on instruction, readiness validation, and deployment preparation consistent with Army regulations issued by the Department of the Army. It interfaces with institutions such as the Reserve Officers' Training Corps, the United States Army Reserve Command, and regional training centers to deliver pre-deployment training and mobilization support. Force modernization initiatives and automation efforts reflect interoperability priorities set by U.S. Northern Command and joint doctrine.

Notable Engagements and Unit Honors

The division’s notable engagements span the late World War I occupation of the Rhineland and the World War II campaigns across Lorraine (department), the Saar Basin, and operations contributing to the encirclement of the Ruhr Pocket. Individual soldiers received awards from the Distinguished Service Cross to the Silver Star (United States), and unit citations recognized participation in major campaigns recorded by the United States Army Center of Military History. Honor rolls include decorations and campaign streamers representing service in the European theatre of World War II and institutional commendations linked to later Reserve mission performance during the Cold War and post–Cold War era.

Category:Infantry divisions of the United States Army Category:Military units and formations established in 1918 Category:United States Army divisions of World War II