Also known as a unit crest or DUI, a Distinctive Unit Insignia is worn by all Soldiers (except General Officers) in units that have been authorized to be issued the device. It is worn centered on the shoulder loops of the Army Green Service Uniform (AGSU) and the blue Army Service Uniform (ASU, Enlisted only) with the base of the insignia toward the outside shoulder seam. DUIs are not worn on the Dress variations of either uniform, however.
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The 21st Aviation Battalion Distinctive Unit Insignia was approved on 5 October 1967. According to the 1985 Army Lineage Series book
Aviation, compiled by Wayne M. Dzwonchyk and published by the Army’s Center of Military History, the design of this insignia “represents the command and supervision of three to seven transport aircraft and/or helicopter companies,” with the area in blue symbolizing the area of control, i.e., the sky. The symbol for man—what many would call an upside-down peace sign—represents the personnel and administrative aspects of the battalion.
A scalloped edge on top of the insignia simulates the appearance of an opened parachute and is an allusion to the unit’s paradrop capabilities. The spread wings encompassing the lower half of the insignia represent both the fixed- and rotary-wing aircraft that were employed by the Battalion. The unit motto of “Peace And War” was a reminder that the unit could be deployed outside time of war if needed in response to a humanitarian crisis or natural disaster.
The 21st Aviation Battalion was constituted as Headquarters and Headquarters Company, 21st Aviation Battalion on 18 April 1967 and activated on 24 June 1967. It was inactivated on 22 November 1971 at Fort Sill, Oklahoma.