4th Cavalry Regiment (United States) companies of the 4th Cavalry to Fort Clark. This time Mackenzie led a larger and more extensive expedition into Mexico, restored a system of patrols, and reestablished peace in the devastated region of South Texas. Outside Texas, Mackenzie and the 4th Cavalry administered and controlled the Kiowa-Comanche and the Cheyenne-Arapaho reservations for several years, and, after the defeat of George Armstrong Custer's command at the Battle of Little Bighorn in June 1876, forced Crazy Horse and his band of Sioux and the Northern Cheyennes to surrender. In the autumn of 1879, Mackenzie with six companies of the 4th Cavalry subdued
5th Cavalry Regiment Henry Thomas. The regiment was rebuilt with new officers and recruits loyal to the Union and was assigned to the Army of the Potomac under the command of General George McClellan. On 21 July 1861, the regiment participated in its first battle of the American Civil War, the First Battle of Bull Run; it was the last action in which they would be called the "2nd Cavalry." In the summer of 1861, all regular mounted regiments were re-designated as "cavalry", and being last in seniority among the existing regiments, the regiment was re-designated as the 5th United States Cavalry. During