In September his Regiment was assigned to the 1st Brigade of Birney's (formerly Kearney's) Division in the 3d Army Corps. It was almost immediately put into most active service. Five days after his first battle (that of Fredericksburg,) Lieut. Horton was made Captain of his Company, viz.: on the 18th of December. On the 4th day of the following May (1863) Captain Horton was engaged with his Regiment in the battle of Chancellorville, Virginia. The Regiment went into this engagement with 419 men, and during the fight had 234 killed or wounded; and for its firm constancy and bravery was warmly complimented, both by General Birney and General Graham. At Gettysburg, Pennsylvania, in July, 1863, this Regiment was again actively engaged. And of Capt. Horton, Gen. Madill, in his report says: "Capt. Horton, though severely stunned by concussion of shell, remained in the field, and I am greatly indebted to him for his services, _as he was the only Captain left with the Regiment_." On the 3d of July, at Gettysburg, Capt. Horton commanded the Regiment. At the morning roll-call of this fearful day, 198 men answered to their names; of this number, 136 were either killed or wounded. On the 31st of the following January (1864) Captain Horton was commissioned Major, commanding his Regiment. And on the 28th of the next month (February, 1864,) he was commissioned Lieutenant-Colonel, commanding his Regiment until Lee's surrender, April 9th, 1865. On the 12th of May, Col. Horton was wounded, during the engagement at Spottsylvania, Virginia, by a gun-shot through his left forearm and in his left hip. During his wounded condition, he was visited by his uncle, Hon. George F. Horton, M. D., and was tenderly nursed by his sister Louisa, wife of Hon. Uriah Terry. While convalescing, and not yet well enough to take the field, he was appointed on several Courts-Martial, and also had charge of several convoys of new men, conducting them to posts along the southern sea-board. With his Regiment, he was honorably mustered out of the service at the close of the war, May 28th, 1865. Of Col. Horton's old Company "A," consisting of 117 members, there were killed, 16; died, 9; discharged for disability, 20; discharged for wounds, 15; transferred to veteran corps for wounds, 7; transferred to 57th Regiment, Pennsylvania Volunteers, for unexpired term of service, 14; absent in hospital, wounded, 4; dishonorably discharged, 1; leaving, at the mustering out of the Regiment, of the whole 117, only 31. Col. Horton was engaged in the following battles, namely: Fredericksburg, Cedars, Chancellorville, Gettysburg, Wilderness, Spottsylvania, Petersburg, Weldon Railroad, White-Oak Road, Sailors' Creek, and at Lee's surrender; besides participating in many small skirmishes. Honorably freed from his military service by the happy close of the war, Col. Horton hasted home to be the business stay of his aged father, and was actively engaged in mercantile pursuits up to 1871.