91st Engineer Battalion
"Honed Sappers"

As part of the Army's transformation towards a modular force, the 91st Engineer Battalion was inactivated at Fort Hood, Texas on 8 July 2005. As part of the modular transformation various assets that had previously been held at division level, but habitually attached to brigades during operations were made organic to those brigades. Headquarters and Headquarters Company, 91st Engineer Battalion was reflagged as Headquarters and Headquarters Company, Special Troops Battalion, 2nd Brigade Combat Team, 1st Cavalry Division in the process.

The coat of arms for the 91st Engineer Battalion, "Honed Sappers," was originally approved on 22 Nov 1939. It was amended on 16 Mar 1999 to add a crest. The shield was red with a plate (white), which were the colors of the Corps of Engineers, and the masoned bridge charged thereon represented engineering accomplishment. The demi-sunburst referred to World War II campaigns in the East Indies. The fountain represented the Pacific Ocean and the Asiatic-Pacific theater of the war. The kris, a typical weapon of Indonesia and Papua, symbolized that region of the Pacific and its significance during World War II. Gold denoted excellence.

The 91st Engineer Battalion was originally constituted on 1 October 1933 in the Regular Army as the 50th Engineer Battalion (Separate). On 1 January 1938, it was redesignated as the 91st Engineer Battalion (Separate) and was activated on 10 February 1941 at Camp Shelby, Mississippi.

On 10 July 1942, the unit was reorganized and redesignated as the 91st Engineer Regiment (General Service) before being redesignated on 6 August 1942 as the 91st Engineer General Service Regiment. The 91st Engineer Regiment was inactivated at Manila, Philippine Islands, on 20 January 1946.

The Regiment (less Headquarters and Headquarters Detachments, 1st, 2nd Battalions and Companies E and F) was reorganized on 28 November 1951 and redesignated as the 91st Engineer Combat Battalion. It was activated at Fort Belvoir, Virginia on 4 January 1952. On 20 May 1953, the unit was reorganized and redesignated as the 91st Engineer Battalion (Combat). The unit was inactivated at Fort Belvoir, Virginia on 20 May 1971.

The 91st Engineer Battalion was reactivated at Fort Hood, Texas, on 16 October 1992 and was assigned to the 1st Cavalry Division. Under the administrative control of the Engineer Brigade, 1st Cavalry Division, the unit was habitually attached to the 2nd Brigade, 1st Cavalry Division during operations.

On 8 July 2005, the 91st Engineer Battalion was inactivated following the inactivation of the Engineer Brigade, 1st Cavalry Division as part of the transformation of the Division to the US Army's modular force structure. As part of the transformation, assets previously held at division level, but habitually attached to brigades during operations were made organic to those brigades. Engineer elements were integrated into the special troops battalions of each of the brigades and the Division itself. Headquarters and Headquarters Company, 91st Engineer Battalion was reflagged as Headquarters and Headquarters Company, Special Troops Battalion, 2nd Brigade Combat Team, 1st Cavalry Division in the process.