166th Infantry Regiment
Assignment not established
The available record does not establish a precise assignment throughout this interval. No division is inferred.
First division shown42d Infantry Division1 Jan 1918
Separate unit histories3 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 Sep 1959; 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.
Approximate wartime windows identify documented affiliations within the labeled years. Their boundaries are coverage limits, not assignment or inactivation orders. Unverified intervals remain visible; common regimental service does not establish the later assignments of each battalion.
Division patches
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.
At a glance
Assignments across time
Bar widths follow elapsed time.
Scroll horizontally on a small screen. Select a segment to open its dated entry. Diamond markers open deployments; their positions indicate the labeled year, not an exact start date or duration. Short assignments are easier to inspect in the list below.
- Division assignment
- 1st Infantry
- 2d Infantry
- 8th Infantry
- Separate headquarters
- Training / academy
- Inactive
- Unverified / last documented
Explore a date
Who were they with?
Look up the dated rows below. Service notes with incomplete dates are excluded; last-documented results do not certify a current assignment.
The dated record
Division timeline
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.
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1 Jan 1916 – 1 Jan 1918
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1 Jan 1918 – 1 Jan 1919
166th Infantry Regiment
42d Infantry Division · Approximate period
Approximate evidence window: the cited history records this wartime affiliation, but these displayed boundaries are not effective-date assignment orders. The date lookup identifies evidence within this window, not confirmed membership on each day.
Deployments & overseas operations
1918
France · World War I
166th Infantry Regiment · Deployment / campaign service
Includes combat or depot/replacement service as described in the regimental history; not every regiment fought as an intact formation.
Source
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1 Jan 1919 – 20 Aug 1943
166th Infantry Regiment
Assignment not established
The available record does not establish a precise assignment throughout this interval. No division is inferred.
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20 Aug 1943 – 22 Jan 1944
166th Infantry Regiment
Training · No assigned division
Division names are normalized across historical redesignations. This entry follows the cited unit lineage.
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22 Jan 1944 – 11 Nov 1946
166th Infantry Regiment
Inactive
The unit or its headquarters lineage was inactive. This status does not imply that every inherited honor or divisional affiliation was erased.
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11 Nov 1946 – 1 Sep 1959
166th Infantry Regiment
37th Infantry Division
Division names are normalized across historical redesignations. This entry follows the cited unit lineage.
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1 Sep 1959 – 15 Feb 1968
1st Battle Group / Battalion lineage
37th Infantry Division
Division names are normalized across historical redesignations. This entry follows the cited unit lineage.
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15 Feb 1968 – 1 Mar 1977
1st Battle Group / Battalion lineage
Assignment not established
The available record does not establish a precise assignment throughout this interval. No division is inferred.
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1 Mar 1977 – 1 Sep 1992
1st Battle Group / Battalion lineage
73d Infantry Brigade · Brigade assignment
This headquarters is not a division. Temporary attachments in the service entries below are distinct from the formal assignment.
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1 Sep 1992 – page cutoff*
1st Battle Group / Battalion lineage
Last documented: Consolidated into another organization
Consolidated, absorbed or redesignated into another organization. Follow the successor’s history rather than assuming continuing independent infantry service. 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.
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1 Sep 1943 – 22 Feb 1944
2d Battle Group / Battalion lineage
Training · No assigned division
Division names are normalized across historical redesignations. This entry follows the cited unit lineage.
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22 Feb 1944 – page cutoff*
2d Battle Group / Battalion lineage
Last documented: Inactive
The unit or its headquarters lineage was inactive. This status does not imply that every inherited honor or divisional affiliation was erased. 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.
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22 Jan 1944 – 12 Feb 1945
3d Battle Group / Battalion lineage
Training · No assigned division
Division names are normalized across historical redesignations. This entry follows the cited unit lineage.
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12 Feb 1945 – page cutoff*
3d Battle Group / Battalion lineage
Last documented: Inactive
The unit or its headquarters lineage was inactive. This status does not imply that every inherited honor or divisional affiliation was erased. 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.
Sources and scope
Army Center of Military History lineage certificates, regimental associations and secondary histories document assignments, operations and battalions. Exact lineage dates and approximate historical coverage are distinguished. 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.
Patch artwork
Unmodified artwork from Wikimedia Commons; individual file pages identify the artist and license. Insignia represent the divisions, not regimental affiliation badges.
- 42d Infantry Division · file and credit · public domain
- 37th Infantry Division · file and credit · public domain
