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.
Full guidance on wear of the DUI is found in DA Pamphlet 670-1,
Section 21-22, "Distinctive unit insignia."♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦
The 509th Personnel Services Battalion Distinctive Unit Insignia, more commonly referred to as a unit crest or by the initialism DUI, was approved with an effective date of 16 August 1995. Its dark blue and scarlet shield features four gold-bordered indentations as well as a trim of gold; dark blue and scarlet refer to its status as a unit in the Adjutant General’s Corps, while gold is the color of excellence and high achievement.
In the dark blue portion of the shield are a crossed sword and quill pen. The quill is an emblem of the Battalion’s administrative duties and its superior execution of them, while the sword is a symbol of military service as well as the individual Soldiers whom the Battalion serves, a mission that is emphasized by the Battalion motto of “Warriors First.” A closer inspection reveals that the sword’s design is of an early Roman type, a reference to the World War II service performed in Italy by forebears in the Battalion’s lineage. This is also recalled by the four pointed indentations that form a stylized version of a mountain range, an allusion to the Apennines in Italy and the Battalion's service there during World War II..
Following its organization on 16 October 1987, the Battalion was activated as a component of 8th Personnel Command. Stationed in Korea, its primary mission was to provide Personnel Services and Postal Support for the 2nd Infantry Division. In June 2005, 8th Personnel Command was inactivated, followed a year later by the inactivation of the 509th Personnel Services Battalion. At the time of the Battalion’s inactivation, it consisted of a Headquarters and Headquarters Detachment, two Detachments (A and B), and the 19th Adjutant General’s Company.