It was reorganized at Newport News, Virginia, and mustered in November 19, 1862, under the command of Colonel John Eugene McMahon.

It was one of the four regiments forming the brigade of Irish soldiers known as the Corcoran Legion.

Corcoran's Brigade, Division of Suffolk, VII Corps, Department of Virginia, to April 1863.

Corcoran's Brigade, King's Division, XXII Corps, Department of Washington, to November 1863.

1st Brigade, Corcoran's Division, XXII Corps, to December 1863.

4th Brigade, 2nd Division, II Corps, Army of the Potomac, to June 1864.

Left New York for Newport News, Virginia, November 6, 1862.

Jerusalem Plank Road, Weldon Railroad, June 22–23, 1864.

Demonstration on north side of James River July 27–29.

Boydton Plank Road, Hatcher's Run, October 27–28.

26% of the men who served would die during the regiment's time of service.