Boatner's "The Civil War Dictionary" notes: "He was appointed B.G. of Cav. in Oct. '64 (although never officially commissioned as such) and served in this position until the surrender, when he was in command of the forces in the front line of the West from Arkansas to the Gulf."

There may be a discussion of his appointment in his memoirs,

Memoirs of the war between the states
by Joseph Lancaster Brent
Published in 1940, Fontana Printing Co. Inc.] ([New Orleans, La)