Infantry timelines · Infantry numbers 1–200

31st Infantry Regiment

A century of division assignments

1916–2026 · Regimental service, battle groups, battalions and deployments.

31st Infantry Regiment unit graphic
31st Infantry Regiment
First division shownPhilippine Division22 Oct 1921
Separate unit histories6 documented elementsDated lineages and service notes below
Page cutoff8 September 2026Last-documented status is explicitly marked

One regiment, separate assignments

The common row follows the regiment. After its reorganization, battle groups and battalions could hold different assignments at the same time. A deployment or temporary attachment does not by itself change the assigned division. The common row closes on 1 Jul 1957; later service belongs to the separate element rows. Battalion rows follow headquarters lineages, often descended from lettered companies, rather than assuming that the old regimental battalions continued unchanged.

The 1941 Philippine Division reassignment is dated only to the year in the Army certificate. That year is shown as uncertain; the division is shown from the following January. Surrender and captivity are distinguished from formal inactivation. The 4th Battalion activation is shown within a 1965 uncertainty window; its brigade assignment is established by the following January. Its 1991 training headquarters briefly carried the Company F designation.

Division patches

Philippine Division7th Infantry Division23d Infantry Division (Americal)10th Mountain Division

Representative division patches. Patterns could change over time; an image does not imply that the exact version was worn throughout every period. Divisions without a verified asset remain identified by name.

The dated record

Division timeline

Battalion overview →

Deployments, operations and credited campaign service appear inside assignment cards. Award years establish credited service, not exact tour dates. Some service notes identify only company-sized elements. This is a sourced selection, not a complete movement log.

Assignment ends are exclusive: the next period starts on that date. *Striped final bars mean last documented, with later status unverified through the page cutoff. Unknown intervals are not treated as inactive.

  1. 1 Jan 1916 – 1 Jul 1916

    31st Infantry Regiment

    Not yet constituted / organized

    This timeline begins in 1916. The cited organization had not yet been constituted or organized during this interval; its formation follows.

    Source

  2. 1 Jul 1916 – 22 Oct 1921

    31st Infantry Regiment

    Assignment not established

    The available record does not establish a precise assignment throughout this interval. No division is inferred.

    Source

    Deployments & overseas operations

    1. 1918-1920

      Siberia

      31st Infantry Regiment · Deployment / overseas operation

      Intervention service with the American Expeditionary Force, Siberia.

      Source
  3. 22 Oct 1921 – 26 Jun 1931

    31st Infantry Regiment

    Philippine Division

    Division names are normalized across historical redesignations. This entry follows the cited unit lineage.

    Source

  4. 26 Jun 1931 – 1 Jan 1941

    31st Infantry Regiment

    No assigned division

    The cited record establishes service outside an assigned division. Higher headquarters and temporary operational attachments could still direct the unit.

    Source

    Deployments & overseas operations

    1. 1932

      Shanghai

      31st Infantry Regiment · Deployment / overseas operation

      Protection of the International Settlement during the Shanghai crisis.

      Source

    2. 1941-1942

      Philippines

      31st Infantry Regiment · Deployment / overseas operation

      Defense of Luzon and Bataan, ending in surrender. The labeled service overlaps an assignment change and is listed only once; consult the following assignment cards as well.

      Source
  5. 1 Jan 1941 – 1 Jan 1942

    31st Infantry Regiment

    Assignment not established

    The available record does not establish a precise assignment throughout this interval. No division is inferred.

    Source

  6. 1 Jan 1942 – 9 Apr 1942

    31st Infantry Regiment

    Philippine Division

    Division names are normalized across historical redesignations. This entry follows the cited unit lineage.

    Source

  7. 9 Apr 1942 – 19 Jan 1946

    31st Infantry Regiment

    Surrendered · Captivity and surviving detachments

    Organized resistance ended in surrender. Captivity and surviving detachments are not treated as normal divisional service or a formal inactivation order.

    Source

  8. 19 Jan 1946 – 1 Jul 1957

    31st Infantry Regiment

    7th Infantry Division

    Division names are normalized across historical redesignations. This entry follows the cited unit lineage.

    Source

    Deployments & overseas operations

    1. 1950-1953

      Korea

      31st Infantry Regiment · Deployment / overseas operation

      Combat service with the 7th Infantry Division.

      Source
  9. 1 Jul 1957 – 1 Jan 1965

    4th Battle Group / Battalion lineage

    Inactive

    The unit or its headquarters lineage was inactive. This status does not imply that every inherited honor or divisional affiliation was erased.

    Source

  10. 1 Jan 1965 – 1 Jan 1966

    4th Battle Group / Battalion lineage

    Assignment not established

    The available record does not establish a precise assignment throughout this interval. No division is inferred.

    Source

  11. 1 Jan 1966 – 15 Feb 1969

    4th Battle Group / Battalion lineage

    196th Infantry Brigade · Separate

    This headquarters is not a division. Temporary attachments in the service entries below are distinct from the formal assignment.

    Source

  12. 15 Feb 1969 – 26 Oct 1971

    4th Battle Group / Battalion lineage

    23d Infantry Division (Americal)

    Division names are normalized across historical redesignations. This entry follows the cited unit lineage.

    Source

  13. 26 Oct 1971 – 2 Oct 1991

    4th Battle Group / Battalion lineage

    No assigned division

    The cited record establishes service outside an assigned division. Higher headquarters and temporary operational attachments could still direct the unit.

    Source

  14. 2 Oct 1991 – 1 Feb 1995

    4th Battle Group / Battalion lineage

    TRADOC · Training

    Institutional or training service. This is a command relationship, not a maneuver-division assignment.

    Source

  15. 1 Feb 1995 – 16 Apr 1996

    4th Battle Group / Battalion lineage

    Inactive

    The unit or its headquarters lineage was inactive. This status does not imply that every inherited honor or divisional affiliation was erased.

    Source

  16. 16 Apr 1996 – 16 Sep 2005

    4th Battle Group / Battalion lineage

    10th Mountain Division

    Division names are normalized across historical redesignations. This entry follows the cited unit lineage.

    Source

    Deployments & overseas operations

    1. 2001-2002

      Afghanistan

      4th Battle Group / Battalion lineage · Deployment / overseas operation

      Elements participated in Afghanistan operations; this was not a single whole-battalion movement.

      Source

    2. 2003

      Horn of Africa

      4th Battle Group / Battalion lineage · Deployment / overseas operation

      Company C and other elements served in Djibouti and Ethiopia.

      Source

    3. 2004-2005

      Iraq

      4th Battle Group / Battalion lineage · Deployment / overseas operation

      Task Force 4-31 operated around Baghdad. The labeled service overlaps an assignment change and is listed only once; consult the following assignment cards as well.

      Source
  17. 16 Sep 2005 – page cutoff*

    4th Battle Group / Battalion lineage

    Last documented: 10th Mountain Division

    Division names are normalized across historical redesignations. This entry follows the cited unit lineage. The source establishes this last recorded status, not uninterrupted service through 2026. The striped bar extends to the page cutoff to keep the later research gap visible.

    Source

    Deployments & overseas operations

    1. 2006-2007

      Iraq

      4th Battle Group / Battalion lineage · Deployment / overseas operation

      A second task force tour south of Baghdad.

      Source

    2. 2009-2010

      Iraq

      4th Battle Group / Battalion lineage · Deployment / overseas operation

      Task force deployment and return to Fort Drum.

      Source

    3. 2015-2016

      Afghanistan

      4th Battle Group / Battalion lineage · Deployment / overseas operation

      Advising and security duties.

      Source

    4. 2018-2019

      Afghanistan

      4th Battle Group / Battalion lineage · Deployment / overseas operation

      Theater response force service.

      Source

    5. 2021

      Kabul evacuation

      4th Battle Group / Battalion lineage · Deployment / overseas operation

      Battalion elements supported the evacuation from Afghanistan.

      Source

Service note · dates incomplete

1st Battle Group / Battalion lineage · Korea

The 1st Battle Group remained with the 7th Division after 1957; the later battalion served in Korea until inactivation in 1987. Exact intervening dates are not established here.

Source

Service note · dates incomplete

2d Battle Group / Battalion lineage · Korea and Fort Ord

The Korean battalion inactivated in 1971, with a later Fort Ord activation in 1974 and inactivation in 1988. The earlier 2d Battle Group at Fort Rucker became the 5th Battalion.

Source

Service note · dates incomplete

3d Battle Group / Battalion lineage · Army Reserve

The 3d Battle Group served in the Army Reserve with the 63d Infantry Division in southern California.

Source

Service note · dates incomplete

5th Battle Group / Battalion lineage · Fort Rucker and Fort Benning

The former 2d Battle Group became the 5th Battalion in 1964. It later served with the 197th Infantry Brigade at Fort Benning and inactivated in 1971.

Source

Service note · dates incomplete

6th Battle Group / Battalion lineage · Vietnam, Cambodia and training

The 6th Battalion served in Vietnam in 1968-1970 and entered Cambodia in 1970. It later served as opposing forces at Fort Irwin, before reflagging in 1988.

Source

Sources and scope

Army Center of Military History lineage certificates provide the dated backbone. Regimental associations and secondary histories supplement individual operations and battalions. Where the evidence stops, the page says so. A page cutoff is not a claim that every unit directory was current on that date.

Earlier battalions are covered by common regimental service; separately dated lineages and substantiated later battalions receive their own rows or notes. A unit graphic alone is not evidence of a battalion assignment. Reserve, training and inactive organizations are distinguished from active combat units.

  1. Army Center of Military History: 4th Battalion 31st Infantry Regiment
  2. Army Historical Foundation: 31st Infantry history
  3. 31st Infantry: legible copy of Army lineage certificate
  4. 31st Infantry Regiment history (Wikipedia; secondary)

Patch artwork

Unmodified artwork from Wikimedia Commons; individual file pages identify the artist and license. Insignia represent the divisions, not regimental affiliation badges.