Thyat bit of information places Cunningham in Carter's 1st Tennessee Cavalry, which formed part of Vaughn's Cavalry Brigade. Here are two lines from the book I listed for you earlier --

As part of Vaughn's Brigade, the regiment moved into Virginia in early 1864, fought at the Battle of Piedmont, or New Hope Church, and in the subsequent campaign in the Valley of Virginia under General Early. On August 22, 1864, Major General Ransom recommended the consolidation of the 12th and 16th Tennessee Cavalry Battalions with the 1st Tennessee Regiment under Colonel Carter, whom he called "a fine officer."