He transferred to the 21st Battalion, Georgia Cavalry, Company C February 24, 1863. Then through the consolidation of units he was transferred to Company B, 7th Regiment, Georgia Cavalry February 13, 1864.

While serving with the 7th Georgia Cavalry in the Army of Northern Virginia, Thomas Brown was captured and after a short stay at Point Lookout, Md. he was moved to Elmira Prison, NY on July 25, 1864.

Pvt. Thomas S. Brown died Jan 14, 1865 of chronic diarrhoea. He was buried at Elmira in grave # 1442.