21st Infantry Regiment Battalions
Modern Era, United States, Infantry
This page collects the existing battalion illustrations and additional documented historical battalions of the 21st Infantry Regiment. The historical entries include inactive units and earlier designations; the regimental image identifies entries without a battalion-specific illustration.
1st Battalion, 21st Infantry Regiment
This entry now anchors the battalion page in the regiment's origin or defining early identity, giving the 1st Battalion slot a more specific historical frame than the first scaffold pass.
The 21st Infantry Regiment traces its lineage to the post-Civil War Regular Army and built its reputation through frontier duty, the Indian Wars, and later overseas service in the Spanish-American and Philippine-American wars. Over time it became one of the long-serving line regiments of the Regular Army.
2d Battalion, 21st Infantry Regiment
The 2d Battalion entry uses the regiment's middle or operational arc to give the page a clearer sense of how the parent unit developed over time.
In the twentieth century the regiment served in major Pacific and Asian campaigns and became especially associated with the Army's fighting in World War II and Korea. Its battalions later carried the lineage into the Vietnam-era Army and then into the Pacific-centered force structure of the late Cold War and after.
3d Battalion, 21st Infantry Regiment
The 3d Battalion entry now carries the regiment into its later or enduring modern identity, tightening the page around the way the lineage is remembered in the modern Army.
Today the regiment survives through battalion lineage rather than a full regimental headquarters, but the 21st Infantry remains identified with the hard-service tradition of the old Regular Army and with modern combat service in the Pacific theater.
4th Battalion, 21st Infantry Regiment
The 4th Battalion served in Vietnam from 1968 to 1971.
Its later service with the 7th Infantry Division included the 1989 intervention in Panama. Army Historical Foundation.
5th Battalion, 21st Infantry Regiment
The 5th Battalion served with the 7th Infantry Division during the late Cold War.
It participated in the 1989 intervention in Panama alongside the regiment's 4th Battalion. Army Historical Foundation.
Research note: The added historical entries cite their sources individually. Regimental illustrations are labeled as such. An earlier battalion designation can continue through another battalion or a separate battery; these relationships are identified in the entries. The original three entries are retained; the additional entries do not treat regimental campaign credits as evidence that every battalion fought in those campaigns.
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