context: The Battle of Chancellorsville was a major battle of the American Civil War (1861–1865), and the principal engagement of the Chancellorsville Campaign.[13] 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, General 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, including Lt. Gen. Thomas J. "Stonewall" Jackson. Jackson was hit by friendly fire, requiring his left arm to be amputated; he died of pneumonia eight days later, a loss that Lee likened to losing his right arm. Lee's difficulty in replacing his lost men as well as his inability to prevent the Union Withdrawal effectively have led to his great victory being regarded as a Pyrrhic one.[14]
question: Who lost the Battle of Chancellorsville?
answers.text: Union Army Maj. Gen. Joseph Hooker's Army of the Potomac General Robert E. Lee's Confederate Army of Northern Virginia