In this letter he is describing what happen to most if not all of the Texas cavalry units that left Texas in the summer of 1862. They were dismounted in Arkansas for two reasons, poor forage and infantry was needed to defend Arkansas and not cavalry. So all of these Texas cavalry units became dismounted cavalry (infantry), they kept their unit designation, but the word (dismounted) was added, thus the 25th became the 25th Texas Cavalry Dismounted. A number of men from each unit was detached and assigned to drive the horses back to Texas. In some cases it took months to complete. If I remember the numbers correctly Texas send about ten cavalrymen for every infantryman, to war at this time. As you can guess these Texas cavalrymen weren't happy about being dismounted, it led to some desertions and almost riots at first. Several Texas units were dismounted near Little Rock, their saddles and tack stored in warehouses in Little Rock and their mounts send back to Texas. I'm sure not all horses were send back to Texas, some took on roles as teams for wagons and artillery, but mules were preferred for these tasks. Some of these Trans-Mississippi (west of the Mississippi River) dismounted cavalry units got remounted later in the war. A note here: a Texas soldier made a drawing of some of the dismounted troops at Camp Nelson, Arkansas. In his drawing he shows many of the men wearing small heeled, tall riding boots. Can you imagne marching around in small heeled riding boots, the boots and your feet would not take it well. In Nancy's song she had it wrong ("These boot weren't made for walking").