Battle of Chancellorsville
Lee defeated Hooker’s Union army, more than twice his size, with a daring division of his forces; but Stonewall Jackson was shot by his own men and died.

Kurz & Allison. · Public domain · Source
At the end of April 1863 Joseph Hooker crossed the Rappahannock with about 130,000 men to trap Lee’s 60,000. Lee split his army and on 2 May sent Jackson’s corps through the woods to strike the exposed Union right flank, routing an entire corps. Hooker withdrew across the river on 6 May.
It is reckoned Lee’s greatest victory, but the Confederates lost some 13,000 men. Returning from a reconnaissance on the night of 2 May, Jackson was hit by fire from his own troops; his left arm was amputated, and he died of pneumonia on 10 May. Emboldened, Lee invaded the North again, heading toward Gettysburg.