Iron Brigade and was previously called the "Black Hat" Brigade. The 3rd Brigade Combat Team, 1st Infantry Division was known as the Iron Brigade from its formation in 1917 through World War I, World War II and Vietnam, until some time in the early 2000s when, for reasons that are still unclear, the name was changed to Duke Brigade. The unit crest was an Iron Cross in a triangle, it appears that that was also changed. The 3rd Brigade of the 4th Infantry Division is also known as the Iron Brigade. Its unit crest is similar to the medals issued to veterans
Battle of the Iron Triangle the Triangle. The ARVN was strong with infantry, armor, and mutually supporting fire bases and outposts in Bến Cát District east of the Thi Thinh boundary of the Triangle, but only one bridge, a weak span, connected the district town and the Triangle hamlet of An Dien. On 16 May the PAVN 9th Division began their attack on with heavy artillery, rocket, and mortar concentrations falling on Rach Bap, Base 82, and An Dien. The RF company at Base 82 abandoned its bunkers, many of which had collapsed under the weight of the bombardment, late that afternoon. Rach Bap held