Union luck was not any better in the east. Burnside had the notion in late January to dislodge the Army of Northern Virginia from Fredericksburg by marching his army up the Rappahannock to where it could ford the stream, then descend on Lee's rear. He put such a movement in motion, but then faced three days of cold rain that turned dirt roads to mud pits along which cannon could scarcely move. Burnside canceled the expedition, and the Army of the Potomac returned to its camp across the river from Fredericksburg even more discouraged than before. Because he was both uninspired and unlucky, most people agreed that Burnside had to be replaced. One of his subordinates, General Joseph Hooker, was selected to take over Burnside's command. The new Army of the Potomac commander was arrogant and vain, but he was well liked by his men, had fought well in the Peninsula Campaign and at the Battle of Antietam, and showed tremendous promise.

Hooker decided that Burnside's plan, which had the misfortune of ending in the “Mud March,” had merit. He decided to attack Lee on two fronts. He left a third of his 115,000 troops near Fredericksburg to keep Lee's army busy there and took the remainder of his men up and across the Rappahannock to engage Lee's relatively unprotected left flank and rear.

Hooker Versus Lee

The first part of the plan went well. Late in April, Hooker got the Army of the Potomac up the Rappahannock and across the river without much fuss, then occupied the crossroads of Chancellorsville about eight miles from Lee's rear. He was confident that he could destroy Lee's army by pressing him from two sides with overwhelming numbers. But Hooker failed to take into consideration Lee's considerable military skills. With just 60,000 troops, Lee used the same tactic that had brought him victory at the Second Battle of Manassas: he divided his troops, leaving 10,000 men at Fredericksburg and taking the rest to meet Hooker's force behind him.

The Stealth Attack

On May 1, Stonewall Jackson surprised Hooker's men as they moved toward the Confederate line. Hooker lost his nerve and ordered a withdrawal. Major General Jeb Stuart notified Lee that Hooker's right flank was vulnerable, so Lee divided his forces a second time. Jackson and 26,000 men marched in stealth to the end of Hooker's right flank and attacked, forcing the Union soldiers into a two-mile withdrawal.

But Lee's grand victory was tempered by bad news: Jackson had been severely injured when Confederate troops mistook him and his mounted staff for Union cavalry and opened fire. He died a week later. Stuart assumed command of Jackson's infantry and launched another attack against Hooker's army on the morning of May 3.

Meanwhile, a portion of Lee's army helped defend his men at Fredericksburg, where they were being threatened by Union troops under General John Sedgwick. After a day-long battle, Sedgwick retreated, joined by Hooker the following day. The Union army suffered more than 17,000 casualties in the battle; the Confederacy lost about 13,000.

Many historians consider the Battle of Chancellorsville Lee's greatest victory. Greatly outnumbered, he out-thought and outmaneuvered his opponents. His victory opened up strategic options for him and put the Army of the Potomac on the defensive.