21st Infantry Regiment

21st Infantry Regiment
Unit name	21st Infantry Regiment
Dates	1861–present
Country	United States
Branch	United States Army
Type	Infantry

21st Infantry Regiment is a United States Army infantry regiment with a lineage tracing to the American Civil War, the Indian Wars, the Spanish–American War, the Philippine–American War, both World Wars, the Korean War, the Vietnam War, and operations in the Global War on Terrorism. The regiment has been assigned to multiple divisions and brigades, serving in campaigns that include the Peninsula Campaign, the Siege of Santiago, the Moro Rebellion, the Meuse-Argonne Offensive, the Korean Peninsula, the Central Highlands of Vietnam, and operations in Iraq and Afghanistan.

History

Originally constituted in 1861, the regiment served during the American Civil War, participating in Eastern Theater operations and later in Reconstruction-era duties; it subsequently engaged in postwar frontier campaigns against Native American nations during the Indian Wars and in expeditionary campaigns such as the Spanish–American War and the Philippine–American War. In World War I the regiment was federalized and deployed to France as part of American Expeditionary Forces, participating in the Meuse-Argonne Offensive and cooperating with units from the French Army and the British Expeditionary Force. During World War II elements served in the Pacific Theater, operating in campaigns that intersected with the Imperial Japanese Army and coordinating with the United States Marine Corps and United States Navy. In the Korean War the regiment fought on the Korean Peninsula alongside United Nations forces, engaging in actions against the Korean People's Army and the People's Volunteer Army. In Vietnam the regiment operated in the Central Highlands and coastal provinces, performing counterinsurgency against the Viet Cong and the People's Army of Vietnam. In the 21st century the regiment's battalions deployed to Southwest Asia for operations including Operation Iraqi Freedom and Operation Enduring Freedom, integrating with multinational coalitions and partnering with host-nation security forces.

Lineage and Honors

The regiment's official lineage records multiple activations, inactivations, and redesignations tied to Army reorganizations such as the Combat Arms Regimental System and the United States Army Regimental System. Campaign streamers awarded include credits for Civil War engagements, Indian Wars actions, Spanish–American War operations, Philippine Insurrection, World War I campaigns like the Meuse-Argonne Offensive, World War II Pacific campaigns, the Korean War, the Vietnam Counteroffensives, and Global War on Terrorism campaigns. Decorations include unit citations and foreign awards presented by governments such as the Republic of Korea and the Government of the Philippines, and unit commendations from the Department of the Army and allied commands. The regiment's heraldic honors reflect participation alongside formations including the 1st Infantry Division, the 24th Infantry Division, the 25th Infantry Division, and subordinate brigade combat teams.

Organization and Structure

Over time the regiment has been organized into battalions, companies, and platoons consistent with United States Army infantry doctrine, with assignments to divisions, regimental combat teams, and brigade combat teams such as the 4th Brigade Combat Team and the 3rd Brigade Combat Team of various divisions. Organizational changes followed structural reforms including the Pentomic reorganization and the later reconfiguration under the Modular Brigade Combat Team concept. Each battalion maintained organic rifle companies, weapons companies, and support elements, coordinating with assets from the United States Army Aviation Branch, Field Artillery Branch, and Combat Support units for combined-arms operations. The regiment's training and readiness cycles interfaced with institutions such as the United States Army Training and Doctrine Command, Fort Benning, Fort Bragg, and corps headquarters.

Operational Deployments

The regiment's operational history encompasses participation in major 19th-century campaigns, expeditionary deployments to the Philippines and Cuba, expeditionary and occupation duties in the postwar periods, large-scale conventional warfare in the two World Wars, counterinsurgency in Korea and Vietnam, and stability operations in the Middle East. Specific deployments included World War I service with the American Expeditionary Forces in France, World War II Pacific operations alongside the United States Marine Corps and Allied navies, major combat operations during the Korean War under United Nations Command, air-mobile and mechanized operations in Vietnam linked to III Corps (South Vietnam), and 21st-century rotations to Iraq and Afghanistan supporting Multinational Force – Iraq and International Security Assistance Force missions. During these deployments the regiment coordinated with air support from the United States Air Force and multinational partners.

Insignia and Traditions

Regimental insignia and heraldry include distinctive unit insignia and coat of arms approved by the Institute of Heraldry (United States), incorporating symbols that reference service in Cuba, the Philippines, France, Korea, and Vietnam, as well as colors associated with infantry lineages like those of the Infantry Branch (United States Army). Traditions include regimental marches, unit mottos, and observances tied to battle anniversaries shared with associated formations such as the 1st Cavalry Division and regional posts including Fort Lewis. Ceremonial practices reflect Army regulations and customs performed during reunions with veteran organizations like the Veterans of Foreign Wars and American Legion.

Notable Personnel and Commanders

Among officers and enlisted soldiers who served with the regiment were commanders and decorated veterans who later held high rank and received awards such as the Medal of Honor, the Distinguished Service Cross, and the Silver Star. Some alumni advanced to prominent commands within the United States Army, the Department of Defense, and national leadership roles, while others are noted in regimental histories and biographical works documenting actions in campaigns like the Meuse-Argonne Offensive, the Battle of Manila (1945), the Battle of Pusan Perimeter, and Vietnam engagements. The regiment's legacy is preserved in unit histories, museum collections associated with National Museum of the United States Army, and archival materials held by military history repositories.

Category:Infantry regiments of the United States Army