The Battle of Chancellorsville, fought from April 30 to May 6, 1863, is widely considered to be Confederate Gen. Robert E. Lee’s greatest victory during the American Civil War. Facing an enemy force nearly twice the size of his own, Lee daringly split his troops in two, confronting and surprising Union Gen. Joseph Hooker. Though Hooker still held numerical superiority, he did not press this advantage, instead falling back to defensive positions. When Lee once again split his forces and attacked, Hooker was forced to retreat across the Rappahannock River, after having lost 17,278 casualties to Lee’s 12,826. Lee’s victory came at a high cost, however. Thomas “Stonewall” Jackson, one of his most trusted generals, was mortally wounded by friendly fire during the battle. Despite the irreplaceable loss, Lee now possessed the strategic initiative, which in a few weeks would lead him north to Gettysburg.