Tom,

Let me start with the Texas 1st Infantry Battalion organized in McLennan County in 1861. Then increased to a regiment and designated as the 15th Texas Infantry Regiment, August 1862. First Commander: Leutenant Colonel then Colonel James W. Speight.
James E. Harrison ( Major, Lieutenant Colonel, Colonel).
John W. Daniel ( Major, Lieutenant Colonel ).

Battles:

Stirling's Plantation - Sept. 29th 1863.
Teche Campaign - Oct. 3rd - Nov. 30th, 1863.
Bayou Bourbeau - Nov. 3rd, 1863.
Red River Campaign - March - May 1864.
Camden Expedition - March - May 1864.

Did you have family in the 15th Texas ?
I saw a Pvt. C. F. Hughes in Co. G from Navarro County.

I hope this helps,
Gary D. Bray