The 66th Armor Regiment Distinctive Unit Insignia, commonly referred to as a unit or or as a DUI, was approved on 11 October 1923. The Regiment’s coat of arms, from which this shield was taken, was first approved for the 15th Tank Battalion, part of belonged in the old 304th Tank Brigade (see below). The color of the shield is the same as the Tank Corps shoulder sleeve insignia. An inescutchecon (small shield in supper left) displays the arms of Langres, reflecting the location where the unit’s original brigades were organized, but the with a silver border and silver crosses rather than red. Not seen on the unit crest is SEMPER IN HOSTES, the unit motto which is Latin for “Always Into The Enemy” and which is the basis of the Regimental song.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.
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Originally organized in August 1918 in the A.E.F. in France as HQ and HQ Companies, 1st and 2nd Provisional Brigades, Tank Corps, the 66th Armor Regiment is the oldest Armor unit in the Army. These two brigades would go on to take part in three World War I campaigns before they were redesignated as the 304th and 305th Tank Brigades, Tank Corps just before the end of the war.
The Brigades were consolidated and redesignated as HHC, 1st Tank Regiment on 22 June 1921; the Regiment would not be given its current numerical designation until 25 October 1932 when it was named the 66th Infantry (Light Tanks). It became the 66th Armored Regiment and was assigned to the 2nd Armored Division on 15 July 1940. During World War II, it earned seven campaign streamers, two of them (Algeria-French Morocco and Sicily) with Arrowhead devices, as well as three Presidential Unit Citations. The Regiment was broken up in March 1946 and its elements redesignated as elements of the 2nd Armored Division; these units combined to fight in eight Korean War campaigns.
In 1957, many of the elements formerly in the Regiment were brought together to form the 66th Armor, a regiment in the Combat Arms Regimental System. It was withdrawn from that system and reorganized under the U.S. Army Regimental System in 1983, earning battle honors for all three campaigns in the First Gulf War and a Valorous Unit Award. Only the 1st and 3rd Battalions have remained active since the War on Terrorism was launched, and both have deployed in support of Operations Iraqi Freedom and Enduring Freedom; both received a Valorous Unit Award for combat action between 3 April and 15 March 2004 in Iraq.
As of Summer 2023, the 1st Battalion is assigned to the 3rd Armored Brigade Combat Team, 4th Infantry Division and is stationed at Fort Carson, Colorado, while the 3rd Battalion is part of the 1st Armored Brigade Combat Team, 1st Infantry Division and is based at Fort Riley, Kansas.