On April 27, 1863, the Army of the Potomac marched North towards the Rappahannock River and Rapidan ford. Within three days, they had 70,000 Federals to face the flank of General Lee. Lee, however, caught on to the scheme of General Joseph B. Hooker in time to counter it. Rather than retreat, Lee opted to attack Hooper while he was still within the thick woods. Hooker had crossed the Rappahannock fords on April 30th and assembled his army of the Potomac on the vulnerable flank of General Lee. On May 1st, Generals Lee and Jackson had a bold plan. Jackson, with his 30,000 Confederates, would follow the trail to the Union right and conduct an attack on that exposed flank. Meanwhile, Hooker left 10,000 troops at Fredericksburg and sent 45,000 men towards Chancellorsville. The Union defeated the Confederates by attacking the Confederate flanks. This attack is where General "Stonewall" was wounded in the left arm and right hand, necessitating the amputation of his arm. Afterwards, he died of pneumonia.
May 3, 1863, the Confederates resumed their offensive and drove the larger part of the army of General Hooker back to a new defensive line nearer the fords. Swinging east, Lee then defeated a separate Federal force near Salem Church that had threatened his rear. Lee's victory at Chancellorsville is widely considered to be his greatest of the entire war.