In the Eastern theater, the Union Army of the Potomac, commanded by Major General Joseph Hooker, attacked the Confederate Army of Northern Virginia commanded by General Robert E. Lee in the Battle of Chancellorsville. Hooker planned to moved most of his army around to the Confederates's rear before Lee could react and force Lee to retreat but the Union army was slowed and then stopped by a small Confederate force, which was reinforced by the rest of the Confederate army. Lee then sent a flanking column led by Thomas J. Jackson around Hooker's left, which attacked a few hours before sunset on May 2; this attack and further Confederate attacks the following day forced Hooker to retreat on May 6. During the battle, Jackson was wounded by friendly fire and died several days later. Lee reorganized his army following the campaign and launched an invasion of Union territory in June, moving through the Shenandoah Valley into Pennsylvania; Hooker was relieved of command on June 29, due to continuous disputes with the government over the garrison of Harpers Ferry, and replaced by Major General George Meade. During the Battle of Gettysburg from July 1 to July 3, Meade successfully held off Lee's attacks while inflicting heavy casualties in return. Lee was forced to retreat back to Virginia; Meade followed in close pursuit but was unable to find an opportunity to completely crush the Confederate army. In October, Lee attempted to isolate and destroy Meade during the Bristoe Campaign but failed in an attack on Union positions at the Battle of Bristoe Station on October 14. Pressed by Union authorities, Meade also tried to attack Lee's positions along the Mine Run; however, Lee was able to establish a fortified defensive line across the Union line of advance. Meade judged the Confederate position too strong to attack and retreated.