The 173rd Infantry Regiment began its existence when it was allotted 20 December 1920 to the Alabama National Guard as the 39th Tank Company, an element of the 39th Division. It was redesignated as the 31st Tank Company in July 1923 and then as Company B, 193rd Tank Battalion and relieved from assignment to the 31st Division in September 1940. Inducted into Federal service on 6 January 1941, it would serve in the Central Pacific and Ryukyus campaigns in the Asiatic-Pacific Theater before it was inactivated on 21 January 1946; it was redesignated as the 131st Tank Battalion on 13 November 1947 and then as the 131st Heavy Tank Battalion from February 1950 to September 1950 when it was redesignated as the 131st Tank Battalion again.
Between 1950 and 2000, the Regiment would be ordered into Federal service four times and redesignated just as often, but it did not deploy to a combat zone again until after the launch of the War on Terrorism in 2001, so the biggest changes during that period involved reorganization. In 1959, the Battalion was reorganized and redesignated as the 131st Armor, a parent regiment in the Combat Arms Regimental System (CARS) consisting of the 1st Medium Tank Battalion. In 1968, it was reorganized to consist of the 1st Battalion, an element of the 30th Armored Division—but the 30th Armored Division’s days were numbered. When the 30th Armored was deactivated in November 1973, its assignment changed to the 31st Armored Brigade.
In 1989, the 131st Armor Regiment was withdrawn from CARS and reorganized under the U.S. Army Regimental System, but the big change came on 1 September 2008: it was reorganized/redesignated as the 131st Cavalry Regiment. It served under this designation for slightly over eight years when, on 11 September 2016, it was reorganized and redesignated not as Armor or Cavalry, but rather Infantry—the 173rd Infantry Regiment in the Alabama Army National Guard, to be precise, consisting of a single battalion (1st) assigned to the 256th Infantry Brigade Combat Team. Today, the 1-173 INF is under the command and control of the 62nd Troop Command.
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As a result of all these changes, the 173rd Infantry Regiment Distinctive Unit Insignia, commonly called a unit crest as well as a DUI, has been authorized for wear by four types of units in three distinct branches of the U.S. Army—Armor, Cavalry and Infantry—in the Alabama Army National Guard. It was first approved on 29 August 1951 for the 131st Tank Battalion, then redesignated for the 131st Armor on 13 December 1960; the second two approval dates can be seen above. It was given its current designation with an effective date of 1 September 2016.
The colors yellow and green in the insignia are those of armored organizations, the unit’s original branch designation, A black annulet simulates a link of chain mail symbolizes Armor (it may also be taken as the letter "O" standing for "Ozark," the area where the unit was organized.) The war club interlaced with the annulet represents World War II combat service in the Central Pacific. "Taught To Lead" is the unit motto.
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.