Pope had been relieved after his dismal showing at 2nd Manassas, and the Army of Virginia was dissolved and absorbed into the Army of the Potomac under McClellan. It was McClellan who stopped Lee's advance into Maryland at Antietam on September 17, but he failed to follow-up and thereby lost an opportunity to destroy Lee's army. When added to his lack of success on the Peninsula and his very public ambitions for the Presidency, that was sufficient reason to relieve him of command. Lincoln did just that, replacing him with Ambrose E. Burnside on November 9, 1862. Burnside had twice declined command of the Army of the Potomac because he doubted his own abilities, and events soon confirmed that those doubts were well founded.
Given the fate of his predecessors, all of whose tenures had been curtailed at least in part due to their lack of initiative, it would be surprising if Burnside did not feel some pressure to take the offensive against Lee. His plan was to move rapidly to Fredericksburg, cross the Rapahanock and then march on Richmond. Unfortunately for the Army of the Potomac, the pace of this movement was not rapid enough to prevent Lee from occupying the high ground behind Fredericksburg, where he created a virtual fortress. Rather than employ maneuver to force Lee out of these defenses, Burnside chose a frontal assault. Given the disparity in numbers; 225,000 Federals to 90,000 Confederates, this tactic might have succeeded if executed with skill. It was not, and the cost to the Union was 1,284 killed, 9,500 wounded and 1,769 captured or missing. Pontoon bridges were thrown across the Rapahanock early on December 11, and after some sharp fighting the crossings were secured and Fredericksburg occupied. The 12th was spent preparing for the assault on Lee's forces, which occurred with disastrous results on the 13th. Still unable to accept the futility of further attack, Burnside planned to personally lead another assault on December 14, but his Corps Commanders prevailed on him to abandon this doomed effort and the army withdrew across the Rapahanock late on December 15.
The 71st had broken camp at Washington on November 1 and marched for Manassas Junction, where it remained for three weeks before moving with the rest of the army to the Rappahannock in front of Fredericksburg. The regiment, having been held in reserve through most of the battle, crossed the Rappahannock late on December 13 in preparation for the final assault Burnside had ordered and planned to lead. Fortunately for the Excelsior Brigade, wiser heads prevailed and the assault was canceled, sparing them the worst of the Battle of Fredericksburg. The 71st suffered only three men wounded in the action. After the disaster at Fredericksburg, and a second failed offensive that bogged down in January rains, Burnside was relieved on January 26, 1863 and Hooker assumed command of the Army of the Potomac. He spent the rest of the winter preparing the Army for a new offensive to be launched in the spring.
Colonel George Hall, commanding the Excelsior Brigade at Fredericksburg, tells us that at "... about 1 o'clock, the brigade was ordered forward; crossed the temporary bridges on the Rappahannock to the other side, and took position, at 3 p.m., immediately in front of the enemy, on the left of the First Brigade, extending our line of battle to the left, next to the right of General J. H. Hobart Ward's brigade, of Birney's division. Soon after taking position, the One hundred and twentieth, under Colonel Sharpe, arrived, and was placed in line in rear of General Ward's (Birney's division) right.
During the early part of the night, I received orders from division headquarters to relieve the right regiment of General Ward's brigade, which was obeyed by advancing the One hundred and twentieth about 30 paces to the crest of the hill in front, General Ward withdrawing his regiment and moving it to his line. Upon arriving in line of battle, skirmishers were immediately thrown out. We were exposed to the enemy upon open ground, with but a slight rise between us, at a distance of about 400 paces. The skirmishers were immediately engaged, and their ammunition (60 rounds) was entirely expended shortly after being posted, owing to the heavy and continued firing of the enemy's sharpshooters, stationed in the trees in front, but the men were promptly relieved from their own commands, until dark put an end to the fire on each side.
Sharp skirmish firing was commenced by the brigade on our right at early light of the 14th instant, and continued till toward afternoon, when they followed the example of this brigade by an agreement with the enemy's skirmishers to stop the desultory firing along the line. During the afternoon the One hundred and twentieth Regiment was withdrawn from their advanced position and placed on the left of the line, extending our line of battle to the right.
No firing took place in our front during Monday, the 15th instant, and at 5 p.m.(having held the enemy in check, and been fifty hours in line) this brigade was relieved by the First Brigade, General Carr commanding; moved back into the road, and bivouacked in line.
About 10 p.m. orders were received to form line in rear of the road about 50 paces, and, after remaining a short time, was ordered to move by the right flank in rear of Seeley's battery. Crossed the Rappahannock in good order, bivouacking about a mile this side. About 10 a.m. on the 16th, the brigade was ordered to proceed toward our old camp, at which place we arrived about 2 p.m. The roads were in a very bad condition from the rain which had fallen the previous night."
An interesting footnote to this report is extracted from the report of BGen Daniel Sickles, commanding the 2nd Division, of which the Excelsior Brigade was a part. "Opportunely, the stretcher-men from my ambulance corps, in going to the front for the wounded skirmishers, occasionally went unmolested to the verge of the enemy's lines to get the wounded of Gibbon's division, who fell on Saturday. These stretcher-men were told by the enemy that, if our skirmishers would not fire any more, our ambulance parties might come anywhere along or within their lines and get all of our wounded, hundreds of whom were heard appealing for succor. This was soon afterward said to be confirmed by General Ewell, whose division was in my front, when I directed all firing along my lines to cease, and by a tacit, though informal, understanding, no more picket firing occurred along my lines. The ambulance men, frequently assisted by the enemy in pointing out our wounded and placing them on stretchers, brought off all of our men who had been left on the field along my front."