I see Kieth beat me to the Shelby and His Men reference, who is most likely the same man. The regimental rosters for Isbell for Co. D, 6th/11th Mo. read the same. He came from Colton Greenes command originally, while it was being reorganized as the 3rd Mo., many men of whom, did not like L. A. Campbell as the Lt. Col. Men transferred out of that command to Shelby's Brigade, if they had connections in that organization and from the looks of it that is what Isbell had. He was cetainly connected with some well known hot blooded characters.