That night, as Lee and Jackson were working on a battle plan for the coming day, cavalry scouts reported that the Federal right wing was "in the air" and vulnerable to attack. This vital information presented the two generals with the opportunity to strike a decisive blow, and once again the Confederates boldly split their forces. Setting out before dawn on May 2, Jackson took 26,000 men on a daring 12-mile march across the enemy’s front to attack the exposed western end of the Federal position. Lee, meanwhile, remained behind with a meager 17,000 men to hold Hooker’s unsuspecting army in place.

Around 5:30 p.m. on May 2, with no more than two hours of daylight remaining, Jackson completed the march and promptly launched his attack. Totally unprepared and hit in the flank, the Federals were utterly routed and sent fleeing back toward Chancellorsville. When his advance stalled in the darkness, Jackson rode out beyond the front to survey the ground over which he hoped to launch a night attack. At the turning point of perhaps his most brilliant campaign, Jackson was accidentally shot and mortally wounded by his own men.

All through the night the stunned Union troops closed ranks and desperately prepared new defensive lines. At dawn on May 3, the rebels reopened the battle with a series of furious assaults from the west. Lee, sensing victory, kept up the pressure all morning with supporting attacks from the south and east. Finally, with all the fight gone out of him, Hooker ordered his army to fall back to protect the roads to the river fords. That same day the Federals at Fredericksburg did manage to drive the Confederate covering force from the heights above the town, but swift rebel counterattacks on May 4 likewise sent these Yankees running for the river. Now forced to admit that his campaign was a failure, Hooker ordered the withdrawal of his army. By the morning of May 6, the Army of the Potomac was safe on the north bank of the river, where it was left to lick its wounds and take stock of yet another resounding defeat.