I know this thread is 4 years old and perhaps the question's already been resolved, or noboy's interested anymore, but I thought I'd add what little I can to the thread, just for the sake of future researchers. If the man referred to was indeed a member of the 24th Missouri Infantry, it appears that his name was misspelled and his rank inflated. According to Lyon's Legion by J. Randall Houp (a history of the 24th Mo. Inf.), the likely individual would be Pvt. Dudley Clanton, a Private in Company D at the outset of the war, but subsequently a member of Company G for most of his three years in the regiment. There was no indication in the book that Clanton was on detached service of any type in early 11864 (although I haven't personally seen his compiled military service record). He was discharged at St. Louis in October 1864, which is when and where the full regiment began mustering out.

This regiment accompanied Banks on the Red River Campaign in March-May 1864, but it appears your letter was written on February 3, and at that time the 24th was in western Tennessee, about to embark on Sherman's Meridian Campaign. Nothing even remotely suggesting Texas shows up until some of the 24th Missouri's soldiers from Red River Caampaign get shipped off to Tyler, TX as POWs. And it seems certain that Dudley Clanton was not one of them.

It is interesting to note, however, that Houp lists Dudley Clanton as dying in January 1885 at Red River Station, Montague County, Texas, and also shows his widow (the former Lucinda Stone of Missouri) as applying for a pension from that state. Her residence in 1890 was Belcherville, also in Montague County, TX. Finally, if anyone wants to track Dudley Clanton in a pre-war census, Houp reports his birthplace as Mount Pleasant, Maury County, Tennessee (circa 1829) and his place of residence at time of enlistment as Laclede County, Missouri.

Kerry Day