The Battle of Chancellorsville was a major battle of the American Civil War, and the principal engagement of the Chancellorsville Campaign. It was fought from April 30 to May 6, 1863, in Spotsylvania County, Virginia, near the village of Chancellorsville. Two related battles were fought nearby on May 3 in the vicinity of Fredericksburg. The campaign pitted Union Army Maj. Gen. Joseph Hooker's Army of the Potomac against an army less than half its size, Gen. Robert E. Lee's Confederate Army of Northern Virginia. Chancellorsville is known as Lee's "perfect battle" because his risky decision to divide his army in the presence of a much larger enemy force resulted in a significant Confederate victory. The victory, a product of Lee's audacity and Hooker's timid decision making, was tempered by heavy casualties and the mortal wounding of Lt. Gen. Thomas J. "Stonewall" Jackson to friendly fire, a loss that Lee likened to "losing my right arm."
The Chancellorsville Campaign began with the crossing of the Rappahannock River by the Union army on the morning of April 27, 1863. Union cavalry under Maj. Gen. George Stoneman began a long distance raid against Lee's supply lines at about the same time. This operation was completely ineffectual. Crossing the Rapidan River via Germanna and Ely's Fords, the Federal infantry concentrated near Chancellorsville on April 30. Combined with the Union force facing Fredericksburg, Hooker planned a double envelopment, attacking Lee from both his front and rear.
On May 1, Hooker advanced from Chancellorsville toward Lee, but the Confederate general split his army in the face of superior numbers, leaving a small force at Fredericksburg to deter Maj. Gen. John Sedgwick from advancing, while he attacked Hooker's advance with about 4/5ths of his army. Despite the objections of his subordinates, Hooker withdrew his men to the defensive lines around Chancellorsville, ceding the initiative to Lee. On May 2, Lee divided his army again, sending Stonewall Jackson's entire corps on a flanking march that routed the Union XI Corps. While performing a personal reconnaissance in advance of his line, Jackson was wounded by fire from his own men, and Maj. Gen. J.E.B. Stuart temporarily replaced him as corps commander.
The fiercest fighting of the battle—and the second bloodiest day of the Civil War—occurred on May 3 as Lee launched multiple attacks against the Union position at Chancellorsville, resulting in heavy losses on both sides. That same day, Sedgwick advanced across the Rappahannock River, defeated the small Confederate force at Marye's Heights in the Second Battle of Fredericksburg and then moved to the west. The Confederates fought a successful delaying action at the Battle of Salem Church and by May 4 had driven back Sedgwick's men to Banks's Ford, surrounding them on three sides. Sedgwick withdrew across the ford early on May 5, and Hooker withdrew the remainder of his army across U.S. Ford the night of May 5–6. The campaign ended on May 7 when Stoneman's cavalry reached Union lines east of Richmond.