The 251st Air Defense Artillery Regiment Distinctive Unit Insignia, also called a unit crest or DUI, was originally approved on 9 January 1928 for the 251st Coast Artillery (Harbor Defense) and was amended on 16 June 1928 to add the motto, “We Aim To Hit.” On 7 January 1952, it was redesignated for the 746th Antiaircraft Artillery Gun Battalion and then for the 251st Artillery Regiment on 16 February 1961. It was given its final designation on 10 July 1972.
A red shield is used for the insignia to reflect the organization’s status as an Artillery organization. Six red, vertical sections, called pallets, stand for the six batteries that made up the Regiment at the time it was organized. The sailing ship is a rendering of the Don Juan Rodrigues Cabrillo, the Portuguese explorer who discovered San Diego Harbor.
In the upper left is a blue canton (inset) containing a fleur-de-lis encircled by laurel, an image taken from the cat of arms of the 250th Coast Artillery (the 251st Coast Artillery’s B Battery descended from the 250th Coast Artillery’s F Battery, the latter which served in World War I as B Battery, 65th Coast Artillery).
Originally organized on 12 October 1881 San Diego City Guard, California National Guard, the 251st Air Defense Artillery Regiment went through several reorganizations that led to its service as an Infantry, Coast Artillery, Antiaircraft Artillery (Gun and Automatic Weapons) unit. In 1966, while still designated as the 251st Artillery in the Combat Arms Regimental System, the Regiment consisted of only the 4th Battalion that had previous been called a Missile Battalion and was armed with Nike and Hercules missiles. It is no longer listed as a unit in the California Army National Guard and it is not clear when the 251st Air Defense Artillery Regiment was inactivated, disbanded, or redesignated.
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The 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.
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.