In June Lee began his campaign into Pennsylvania which eventually led to the battle of Gettysburg. The Fifth New Hampshire arrived on that field late in the evening of July 1 and was held in reserve throughout most of July 2 until about 4:30 in the afternoon when the brigade commanded by Cross, was ordered into the “wheatfield”. In three hours of desperate fighting the regiment lost 86 officers and men of 187 men present for duty. Col Cross was mortally wounded by a musket ball that struck him in the navel and exited near the spine.
With less than one hundred men present for duty after Gettysburg, the army command detached the Fifth from the Second Corps and returned it to New Hampshire for recruits to rebuild their decimated ranks. The men were understandably pleased to return to New Hampshire and the soldiers were granted leaves to visit their homes throughout the state.
From August 3rd through October, the regiment remained in the state receiving conscripts. On November 9th, they arrived by steamer at Point Lookout, Maryland where they, along with the 2nd and 12th New Hampshire, were assigned the duty of guarding Confederate prisoners. Here they remained until May 1864 when they were recalled to the Army of the Potomac. The regiment reported for duty on the eve of the deadly assault at Cold Harbor. Their casualties were 202 killed out of 577 present for duty the most costly single day in the regiments history. In the continuing campaign that developed into the siege of Petersburg, a series of engagements occurred between June 15th and June 19th at Baylor’s Farm, Withal, and Weir Bottom Church that continued to erode the regiments rolls.
From June till the battle of Deep Bottom, VA on August 14th the journals from the members of the regiment show a series of marches and countermarches or simply being prepared to move at a moments notice. The Fifth was not engaged at Deep Bottom but two days later engaged the enemy at Charles City Crossroads. It was during this battle that skirmishers from the Fifth shot and killed Confederate General John R. Chambliss.