During a successful reconnoissance in force October 16th, to Charleston, they were tor the first time under fire, and acted creditably. On their return they went to Bolivar Heights.

On November 23d they were encamped about five miles from Fredericksburg, and on December 13th participated in the battle at that place. On the 15th they recrossed the river and went into camp near Falmouth, where they remained until the close of April, 1863.

On the 27th of April, with their division, they were ordered to co-operate with General Sedgwick in the attack upon the heights of Fredericksburg, and were assigned the duty of guarding the telegraphic communication between the left wing of the army and General Hooker’s headquarters, in which position they remained until May 3d, when they were ordered to Fredericksburg, and on the 5th removed the pontoon bridge at that place, under a severe fire from the enemy.

On the 1 st of July they arrived at Gettysburg and on the 2d and 3d were hotly engaged with the enemy. They went into action with 440 officers and men, and their loss during the two days was 12 officers and 220 enlisted men killed and wounded. Subsequently they crossed into Virginia by way of Harper’s Ferry,_and on the 13th of September co-operated with General Gregg’s cavalry across the Rappahannock, compelling the enemy to fall back beyond Culpepper. They remained on duty on the Rapidan until October 8th, when they returned to Culpeper, and on the 12th engaged the enemy at Bristow Station, losing man killed and 13 wounded. November 26th they joined in the movement to “Mine Run,” and on the 6th of December went into camp at Stevensburg, where they remained until May 3, 1864. On May 4th they crossed the Rapidan at Ely’s Ford, and on the 5th and 6th were engaged with the enemy at Todd’s Tavern and at the Wilderness. Their loss in the several engagements was very severe. On May 10th they formed a portion of a column which twice assaulted the enemy’s position across the Po River, and on the 12th participated in the famous assault of the Second Corps. On the 24th they were engaged with the enemy at the North Anna river, crossed the Pamunkey river on the morning of the 28th, and on the 1st of June  participated in the engagement near Bethesda Church. On the 3d they stormed the enemy’s works at Cold Harbor and lay under a galling fire all day. On the 13th of June they proceeded towards Petersburg, went into position in front of that city on the 15th, formed the extreme right of the assaulting column on the 18th, and afterwards participated in the attack upon the enemy’s inner line of works. On the 22d of June they participated in the engagement near the Jerusalem Plank Road, during which their casualties were numerous and many being prisoners. On the 26th of July they joined in the movement to Deep Bottom, engaged the enemy at that place, and returned in front of Petersburg on the 30th, where they remained encamped until the 15th of August, when they again proceeded to Deep Bottom, returning on the 21st. On the 23d they proceeded to Ream’s Station, and on the following day were engaged in the destruction of the Weldon Railroad. On the 25th they were engaged with the enemy and returned to Petersburg on the 26th. Their loss in this engagement was heavy.

On the 20th of September they moved into the line in the immediate front of Petersburg, where they were exposed to the fire of artillery and sharpshooters day and night until the 26th of October, when they marched across the Weldon Railroad, and on the 27th participated in the engagements at Hatcher’s Run and near the Boydton Plank Road.

On the 31st of October they occupied Fort Haskell, in the front line, exposed as before to the continued fire of artillery and sharpshooters, and remained there until the 30th of November. On that day they moved to near Patrick Station, the terminus of the Grant Railroad, and went into winter quarters.

The regiment left camp May 3, 1864, with 22 officers and 468 enlisted men. Of the 277 men transferred, June 18th, from the Fourth Maine Volunteers, there were in the field, 57 men. A new company, the Fifth of Unassigned Infantry, organized at Augusta, Maine, October 5, 1864, to serve one, two, and three years, joined the regiment, October 22d, with 3 officers and 64 enlisted men; making a total of 25 officers and 589 enlisted men. The casualties during the year 1864 were as follows: Killed in action, 61 men; wounded and died of wounds, 1 officer, 39 men; wounded exclusive of those died of wounds, 16 officers, 283 men; taken prisoners by the enemy, 1 officer, 133 men.

On the 1st of January, 1865, the regiment was encamped in front of Fort Emory, near Petersburg, Virginia, and remained there until February 5th, when, with their division, they joined in the movement to Hatchers Run, and there remained encamped until the 29th of March. On that day they marched out on the Vaughan road and made a successful reconnoissance to Dabney’s Mills, which position they occupied without opposition. On the 30th and 31st of March they were engaged with the enemy at Fort Powell, which they entered on the 2d of April, and afterwards joined in the pursuit of Lee’s forces, overtaking them near Amelia Court House on the 6th of April and pursuing them all day. On the 7th of April they had a spirited engagement with the enemy at High Bridge on the Lynchburg Railroad, and saved from destruction the railroad and foot bridges across the stream.

On the 2d of May they left Burksville for Washington, District of Columbia, and encamped at Baileys Cross Roads on the 15th.

In obedience to orders, the regiment was there mustered out of the United States service, May 31st, by Captain H. Y. Russell, Assistant Commissary of Musters.