Battle of Fredericksburg General McClellan was replaced by General Burnside because of McClellan's loses, on November 7. General Burnside launched a campaign against the Confederate Capitol, Richmond, by way of Fredericksburg, a very important town by the Rappahannock River. On November 17, the Federal Army of the Potomac raced to Fredericksburg. There were only a few thousand Confederates to fight them, but the Federal Army advanced ground to halt the eastern bank of the Rappahannock. The campaign was delayed for over a week when material that Burnside needed failed to arrive. Burnside had to wait for two weeks before he could start the battle. General Lee took advantage of this two-week time period, to entrench his Army of North Virginia, about 78,000, on the ground behind Fredericksburg.
General Burnside crossed the river on December 11, even though the Confederates were firing; they were hidden in buildings along the city riverfront.
When the Confederates withdrew, some of the Federal soldiers robbed the town. By December 13, General Burnside was prepared to launch an attack to drive Lee's forces from the hills just outside Fredericksburg.
The main attack occurred south from Fredericksburg. The Confederate troops formed a line of defense along the fortified hills called Mayre's Heights. This is where the men of the south were hiding behind a solid rock wall. Wave after wave of the Federal attackers were taken out by Confederate troops firing from unknown positions in a sunken road protected by a stone wall. Throughout the day, no fewer than fourteen successive Federal brigades charged the wall of the Confederate fire. Not one of the Federal soldiers reached Longstreet's line.
General Burnside ordered his beaten army back across the Rappahannock River on December 15. The Union had lost 12,700 soldiers that were killed, wounded, missing, or captured. Federal morale plummeted, and General Burnside was relieved of his command. By contrast, the morale of the Confederacy reached a peak. Their causalities were very low compared to the Union's totaling to 5,300. Lee's victory at Fredericksburg was won at almost ease; it increased the confidence of the Army of North Virginia, which led to the invasion of the North the following summer.