It looks like he was taken prisoner at Newtonia, Mo. with a sever wound. Shortly thereafter he was released and exchanged, following which he was discharged for physical reasons resulting from his wounds. Records indicate he later served in some type Home Guard unit.

I believe Texas pensions were first granted ca 1899. He had either died by then, age 80 or so, or may have been ineligible as pensions were granted only for those disabled or indigent.

James P. Smyth, age 45, Orderly (1st) Sergeant, Capt. John H. Duncan’s Company, Hawpe’s Regiment Texas Cavalry (Dismounted),* enlisted March 29, 1862 at San Antonio by Jno, H. Duncan for the war, severely wounded in hip at Newtonia, Mo. September 30, 1862, taken prisoner, recorded present at the Jan/Feb, 1863 muster, discharged March 6, 1863, for inability from wounds received in battle, no further records

* This company subsequently became Company C, 31st Regiment Texas Cavalry

M323: Compiled Service Records of Confederate Soldiers Who Served in Organizations from the State of Texas

…………..

Enlisted April 21, 1862 in Bexar Co. for the war, Age 42, resident of Karnes Co., Company C, T. C. Haupt’s Regiment
Ancestry.com

…………..

Jas. P. Smyth, 2nd Lt., Co. for Karnes County, 3rd Frontier District, TST [Texas State Troops?] Commanding Officer Jas. P. King, 1st Lt., enlisted 1864
Consists of all male citizens, 15-50 in part of Karnes County west of San Antonio River.
No other information
Ancestry.com