1st Infantry Regiment Battalions
Modern Era, United States, Infantry
This subpage highlights the battalion-level identities most closely associated with the modern 1st Infantry Regiment. The 1st and 2d Battalions carry the regiment's active lineage into the present era, while the 3d Battalion section preserves the short but important Vietnam-era battalion that also fought under the regiment's colors.
1st Battalion, 1st Infantry Regiment
The 1st Battalion traces back to Company A of the old 2d Infantry, one of the company lines created in March 1791. That lineage shared the parent regiment's early service on the frontier, in the War of 1812, in Mexico, in the Civil War, in the Philippine campaigns, and in the Pacific during World War II. In that sense, the battalion represents the oldest continuous company heritage inside the regiment.
Its modern form emerged through Cold War reorganizations. After the regiment's post-Korea reactivation and assignment to the United States Military Academy, the old company line became the 1st Battle Group, 1st Infantry, and on 31 December 1964 it was redesignated as the 1st Battalion, 1st Infantry. Since then the battalion has been closely associated with West Point and the academy support mission, carrying the regiment's oldest lineage in an institutional role rather than as a permanently deployed field battalion.
2d Battalion, 1st Infantry Regiment
The 2d Battalion descends from Company B of the same 1791 regiment and therefore shares the deep early history of the parent unit. Like the regiment as a whole, its lineage includes War of 1812 service, the Mexican War, the Civil War, frontier campaigning, the Philippines, and the 6th Infantry Division's Pacific fighting in World War II. After the regiment's return to active duty in 1950, this company line passed through the Pentomic-era designation of 2d Battle Group, 1st Infantry.
Redesignated as the 2d Battalion in September 1965, it became the regiment's principal deployable battalion of the Vietnam War. It served first with the 196th Infantry Brigade and then with the Americal Division, earning campaign credit from Counteroffensive Phase II through the cease-fire period. In later decades the battalion remained the regiment's most visible field battalion, serving with the 9th Infantry Division, the 199th Infantry Brigade, Alaska-based forces, and later Stryker formations in the Pacific Northwest.
3d Battalion, 1st Infantry Regiment
The 3d Battalion is best understood as the regiment's Vietnam-era third maneuver battalion. During the Army's mid-1960s expansion for Southeast Asia, a 3d Battalion, 1st Infantry was activated in Hawaii and assigned to the 11th Infantry Brigade. It reached South Vietnam in December 1967, landing at Qui Nhon before moving into operations from the Duc Pho and Bronco areas in I Corps.
Once the Americal Division formed in theater, the battalion became part of the division's long fight in Quang Ngai Province. Its service was relatively brief compared with the older 1st and 2d Battalions, but it gave the regiment a third active combat battalion during the hardest years of the Vietnam War. After that conflict the 3d Battalion did not remain one of the regiment's enduring active battalions, so its place in the regiment's story is chiefly tied to Vietnam.
Research note: The 1st and 2d Battalion summaries follow U.S. Army Center of Military History lineage material. The 3d Battalion note is a short reconstruction from the parent regiment history and published Vietnam-era unit histories because a battalion-specific CMH sheet was not available in the public index I could access.