Chancellorsville is Lee's masterpiece. It is also the battle that broke the Confederate army in ways that only became visible a month later at Gettysburg.

The Situation, May 1863

Joseph Hooker had replaced Burnside as commander of the Army of the Potomac after the disaster at Fredericksburg and spent the winter rebuilding his force into what he called the finest army on the planet. By late April 1863, he had 134,000 men against Lee's 60,000.

Hooker's plan was genuinely good. He sent cavalry under George Stoneman to cut Lee's supply lines, held a corps demonstrating at Fredericksburg to fix Lee in place, and marched the bulk of his army in a wide flanking arc to the west, crossing the Rappahannock and Rapidan Rivers to emerge at Chancellorsville — a crossroads in the dense second-growth forest called the Wilderness — on Lee's unprotected left flank.

On May 1, Hooker's leading corps pushed east from Chancellorsville and nearly escaped the Wilderness onto open ground, where Union artillery superiority would have been decisive. Then Hooker lost his nerve and ordered his men back to defensive positions around the crossroads.

Lee's Gamble

Lee's response to the situation he faced was one of the most audacious decisions in American military history. With a force half the size of Hooker's, threatened on his front and his left, he divided his army.

Stonewall Jackson would take 28,000 men — nearly the entire force not engaged at Fredericksburg — on a 12-mile march around the Union right flank. Lee would hold the Union center with 14,000 men. If Hooker discovered what was happening and attacked, Lee's holding force would be destroyed.

The march took all day on May 2. Union cavalry spotted the column and reported it. Hooker concluded that Lee was retreating.

At 5:15 p.m., Jackson's corps hit the Union XI Corps in the flank while they were cooking dinner. The corps broke and ran. Jackson's men drove through the forest for three miles before darkness, disorganization, and Union artillery finally stopped them.

The Death in the Dark

That night, Stonewall Jackson rode forward with his staff to reconnoiter. Returning through Confederate lines in darkness, he was fired on by soldiers of the 18th North Carolina who mistook his party for Union cavalry. Jackson was hit by three bullets — two in the left arm and one in the right hand.

His arm was amputated at a field hospital. He developed pneumonia and died eight days later. Lee, informed of the wounding before the amputation, is said to have told an aide that Jackson had lost his left arm, but Lee had lost his right.

Hooker's Collapse

The battle continued for two more days, with Lee performing the extraordinary feat of dividing his army a second time to deal with a Union breakthrough at Fredericksburg. By May 6, Hooker had recrossed the Rappahannock with his entire army intact.

The Union army — 134,000 men — had been defeated by 60,000. Hooker suffered 17,000 casualties; Lee 13,000. By casualty percentage, the Confederates paid more. By strategic result, Hooker was the loser.

The Cost of Genius

Chancellorsville gave Lee the confidence that drove the Gettysburg campaign. It was that confidence — the belief that his army could accomplish anything — that led him to order Pickett's Charge two months later.

More immediately, Jackson's death removed the one Confederate corps commander capable of independent operational thinking. His successors in II Corps at Gettysburg — Richard Ewell and Ambrose Powell Hill — would make critical errors that Jackson likely would not have made. The question of whether the Confederacy could have won at Gettysburg with a healthy Stonewall Jackson remains one of the most debated counterfactuals in Civil War historiography.

Chancellorsville proved Lee's genius. Jackson's death guaranteed that the genius would eventually reach the limit of what one man and one army could accomplish alone.