4:21st Infantry

The 4th Battalion, 21st Infantry Regiment (4/21st Infantry) is a distinguished unit of the United States Army with a storied history dating back to its formation in 1861. The regiment earned battle honors in major conflicts, including the Civil War, Philippine–American War, World War II, and the Vietnam War, where the 4th Battalion was reactivated and participated in operations throughout the I and II Corps Tactical Zones. During the Vietnam War, 4/21st Infantry, known as the "Gimlets," was assigned to the 11th Infantry Brigade, Americal Division, conducting search and destroy missions and counterinsurgency operations. In recent decades, elements of the battalion have supported missions in Iraq and Afghanistan, continuing their legacy of service and adaptability in modern conflicts.