The Battle of Chancellorsville was a major battle of the American Civil War, fought near the village of Spotsylvania Courthouse, Virginia, from April 30 to May 6 1863. The battle pitted Union Army Maj. Gen. Joseph Hooker"s Army of the Potomac against an army half its size, Gen. Robert E. Lee"s Confederate Army of Northern Virginia. It is known as Lee"s "perfect battle"Dupuy, p. 261. because of his risky but successful division of his army in the presence of a much larger enemy force. Lee"s audacity and Hooker"s timid performance in combat combined to result in a significant Union defeat. The Confederate victory was tempered by 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. Crossing the Rapidan River via Germanna and Ely"s Fords, the Federals concentrated near Chancellorsville on April 30 and May 1. Heavy fighting began on May 1 and did not end until the Union forces retreated across the river on the night of May 5 to May 6.