Army - Vietnam Combat Cavalry Veteran With 2nd Battalion 5th Cavalry Distinctive Unit Insignia - 1st Cavalry Division - HoodieThe 5th Cavalry Regiment ("Black Knights") is a historical unit of the United States Army that began its service on August 3, 1861, when an act of Congress enacted "that the two regiments of dragoons, the regiment of mounted riflemen, and the two regiments of cavalry shall hereafter be known and recognized, as the first, second, third, fourth, and fifth regiments of cavalry respectively" and continues in modified organizational format in the U. S.