The following is taken from New York in the War of the Rebellion, 3rd ed. Frederick Phisterer. Albany: J. B. Lyon Company, 1912.

October 4, 1862, Col, James W. Savage received authority from the State to recruit this regiment. It was organized at New York city to serve three years. A number of the men enlisted for the Abohbot Cavalry were transferred to its Company D, November 29, 1862, and in August, 1863, the men enlisted for the 21st Regiment Veteran Volunteers, reorganizing, were also transferred to the regiment. A number of the men enlisted by Capt. G. S. Coddington for the 20th Battery were transferred to this regiment. The companies were mustered in the United States service in New York city, A November 19, 1862, B March 31, 1863, C February 17, 1863, F April 28, 1863; at Buffalo, D and E February 14, and L February 16, 1863. May 20, 1863, the regiment was reorganized as follows: Company A was formed of parts of original Companies A and G; B of parts of original Companies A, B and I; C of original Company C and parts of original Companies D and I; D of original Company E and part of original Company G; E of parts of original Companies F, G and H; F of original Companies D and K; Company L retained its designation. Companies G, H and I were reorganized and mustered in United States service at New York city, Company G August 7th, Company I September 22d; at Buffalo, Company H August 27, 1863. Companies K (second) and M were mustered in at Buffalo, September 10, and at New York city, November 24, 1863, respectively. From September, 1863, to December, 1864, a howitzer section, manned by members of the regiment, formed part of the latter.

The companies were recruited principally: A, originally intended for the 5th Cavalry, at Fulton and Oswego; B at Ogdensburg, Cuba, Copake, Clifton Park, Charlton, Claver-ack, West Troy, Albany and Hudson; C at Austerlitz, Hudson, Hillsdale, Chatham and New York city; D, E, H, old and new, K and L at Buffalo; F at New York city, Platts-burgh, Fort Covington, Dickinson and Rouse's Point; G and I, old, at New York city; G new, at New York city, Syracuse, Oswego, Hudson and Troy; I, new, at New York city, Oswego, Troy and Syracuse; and M at Buffalo, New York city, Troy and Niagara.

The regiment left the State by detachments, the first in May, 1863, and was entirely in the field by December of that year; it served in the Department and District of North Carolina, l8th Corps; and from March, 1865, with the Provisional Corps; with the 23d Corps from April, 1865, and July 19, 1865, commanded by Lieut.-Col. Philip G. Vought, it was honorably discharged and mustered out at Raleigh, N. C.

During its service it lost by death, killed in action, 2 officers, 20 enlisted men; died of wounds received in action, I officer, 16 enlisted men; died of disease and other causes, 5 officers, 178 enlisted men; total, 8 officers, 214 enlisted men; aggregate, 222; of whom 1 officer and 84 enlisted men died in the hands of the enemy.

The following is taken from The Union army: a history of military affairs in the loyal states, 1861-65 -- records of the regiments in the Union army -- cyclopedia of battles -- memoirs of commanders and soldiers, Volume II: New York, Maryland, West Virginia and Ohio. Madison, WI: Federal Pub. Co., 1908.

Twelfth Cavalry.—Col.. James W. Savage; Lieut. -Col., Philip G. Vought; Majs., J. Ward Caspar, Rowland R. West, Floyd Clarkson, Rodney M. Taylor. The 12th cavalry, known as the 3d Ira Harris Guard, was organized at New York city to serve for three years. The companies of which it was composed were recruited in the counties of New York, Columbia, Albany, Rensselaer, Clinton, Franklin, Oswego, Onondaga and Erie, and were mustered into the U. S. service from Nov. 19 to 24, 1863. A howitzer section, manned by members of the regiment, was attached during the year 1864. The regiment left the state by detachments from May to Dec, 1863, and proceeded to North Carolina, where it spent its entire term of service, forming part of the i8th corps under command of Maj. -Gen. J. G. Foster. In the final campaign in 1865, it was assigned to the provisional corps, and from April, 1865, was with the 23d corps, commanded by Maj. -Gen. Schofield. In July, 1863, it shared in Gen. Foster's raid to Tarboro, meeting with a loss of 4 killed, 14 wounded and 2S missing. It also sustained some losses in the engagements near Washington, N. C, in August. It assisted in repelling the enemy's attack on New Berne in Feb., 1864, and participated in the defense of Plymouth in April, where it sustained its heaviest loss, 8 killed and mortally wounded, 11 wounded and 102 captured. Many of the men captured subsequently perished in the prison pen at Andersonville. During the remainder of the year 1864 the regiment took part in numerous raids throughout the state and was often in action, meeting with some loss. In March, 1865, the 12th led the advance of Schofield's column, which was moving to join the forces of Gen. Sherman and fought gallantly in the three days' battle at Wise's Forks, where it lost 62 men killed, wounded and missing. It skirmished almost continuously from Kinston to Goldsboro, its total losses in the campaign of the Carolinas being 134 killed, wounded and missing. After Johnston's surrender the regiment was employed in guard duty in the region about the Tar river until July 19, 1865, when it was mustered out at Raleigh, N. C. It lost while in service 3 officers and 36 men killed and mortally wounded; 5 officers and 178 men died of disease, accidents, in prison, etc., a total of 222. It sustained unusually heavy losses by death in Confederate prisons, I officer and 84 enlisted men dying in the hands of the enemy.