While Lee pounded the Chancellorsville defense line with repeated, costly assaults on May 3, the Union VI Corps, under Maj. Gen. John Sedgwick, finally achieved what Ambrose Burnside could not, by successfully assaulting the reduced forces on Marye's Heights in Fredericksburg. The corps began moving westward, once again threatening Lee's rear. Lee was able to deal with both wings of the Army of the Potomac, keeping the stunned Hooker in a defensive posture and dispatching a division to deal with Sedgwick's tentative approach. By May 7, Hooker withdrew all of his forces north of the Rappahannock. It was an expensive victory for Lee, who lost 13,000 men, or 25% of his army; Hooker lost 17,000, but had a lower casualty rate than Lee had incurred.Furgurson, pp. 257–62, 274–80, 364–65.
