With the consoldation of units, he was transferred to the 7th Regiment, Georgia Cavalry Co. B February 13, 1864, retaining the rank of Captain.
On June 11, 1864 he was captured at Trevillian Station, Va.; sent to Fortress Monroe and on to Point Lookout, Md. on June 20 then to Fort Delaware June 23.
For unknown reasons, he was in the Post Hospital at Ft. Delaware the 1st through 6th of August 1864. Some sources indicate that he was wounded at Trevillian Station.
From Ft. Delaware he was forwarded to Charleston, S.C. on August 20. Here, having been put in a stockade at Charleston Harbor, Captain Miller began his imprisonment as one of the "Immortal 600". Following this, he and the others were moved to Fort Pulaski, Ga. October 21, 1864 where their ordeal continued with the same terrible conditions.
He was returned to Ft. Delaware March 12, 1865, took an oath of allegiance June 10 and was released at which time he returned home to Screven County, Ga.