The campaign Military_operation pitted Hostile_encounter Union Army Maj. Gen. Joseph Hooker 's Army of the Potomac against an army less than half its size , General Robert E. Lee 's Confederate Army of Northern Virginia .

The victory , a product Manufacturing of Lee 's audacity and Hooker 's timid decision-making , was tempered Cause_change_of_position_on_a_scale by heavy casualties Catastrophe , including Lt. Gen. Thomas J .

Combined with the Union force facing Fredericksburg , Hooker planned Arranging a double envelopment , attacking Attack Lee from both his front and rear .

On May 1 , Hooker advanced Self_motion from Chancellorsville toward Lee , but the Confederate general split Destroying his army in the face of superior numbers , leaving Departing a small force at Fredericksburg to deter Hindering Maj. Gen. John Sedgwick from advancing , while he attacked Attack Hooker 's advance with about four-fifths of his army .

On May 1 , Hooker advanced Self_motion from Chancellorsville toward Lee , but the Confederate general split Destroying his army in the face of superior numbers , leaving Departing a small force at Fredericksburg to deter Hindering Maj. Gen. John Sedgwick from advancing , while he attacked Attack Hooker 's advance with about four-fifths of his army .

Despite the objections of his subordinates , Hooker withdrew Escaping his men to the defensive Defending lines around Chancellorsville , ceding GiveUp the initiative to Lee .

Sedgwick withdrew Escaping across the ford early on May 5 , and Hooker withdrew Escaping the remainder of his army across U.S. Ford the night of May 5–6 .