During the Gettysburg Campaign, he was appointed to command the Army of the Potomac just three days before the Battle of Gettysburg. Arriving on the field after the first day's action on July 1, Meade organized his army on favorable ground to fight an effective defensive battle against Robert E. Lee's Army of Northern Virginia, repelling a series of massive assaults throughout the next two days. Lee was forced to retreat to Virginia, ending his hope of winning the war through a successful invasion of the North. This victory was marred by Meade's ineffective pursuit during the retreat, allowing Lee and his army to escape instead of completely destroying them. The Union Army also failed to follow up on its success during the Bristoe Campaign and Battle of Mine Run that fall, which ended inconclusively. Meade suffered from intense political rivalries within the Army, notably with Major Gen. Daniel Sickles, who tried to discredit his role in the victory at Gettysburg.