The 138th Air Defense Artillery Regiment Distinctive Unit Insignia—colloquially referred to as a unit crest or DUI—was approved on 22 November 1989. Scarlet and yellow, the predominant tones, are colors long associated with Air Defense Artillery. The yellow protrusions into the blue are called nebuly, used in heraldry to mimic clouds and signify the sky—the unit’s theater of attack. A red chevron denotes support, and when combined with the lightning bolt it emphasize attack and the pinpoint accuracy the unit displays when it is “Rising To The Defense.”
Little can be gleaned of the origins or lineage of the 138th Air Defense Artillery Regiment from standard sources such as the U.S. Army Center of Military History or even the book Center’s Army Lineage Series book Air Defense Artillery, originally published in 1985 but updated in 2000. Apparently no longer active, the Regiment was organized to consist of the 1st Battalion, which was inactivated in September 1997 but was reactivated following the launch of the War on Terrorism. The 1st Battalion, 138th ADA was recognized for its meritorious service in a peacetime role by being tapped for an Army Superior Unit Award for its performance between 1 September 2004 and 1 March 2005.
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Distinctive Unit Insignias are 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 (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.
Enlisted personnel wear the insignia centered on a shoulder loop by placing it an equal distance from the outside shoulder seam to the outside edge of the shoulder-loop button. Officers (except Generals) wearing grade insignia on the shoulder loops center the DUI by placing it an equal distance between the inside edge of the grade insignia and the outside edge of the button.
Full guidance on wear of the DUI is found in DA Pamphlet 670-1, Section 21-22, "Distinctive unit insignia" and 21–3(d) and (e), "Beret" and "Garrison Cap," respectively.