The Battle of Chancellorsville (April 30 to May 6, 1863) was a major battle in the American Civil War. It is generally considered to be Confederate General Robert E. Lee’s greatest victory over the Union Army. But the Confederate victory was lessened by the loss of Lieutenant general Stonewall Jackson. Jackson was shot and mortally wounded by his own men who mistook the general and his staff for Union cavalry. For this reason Lee's win at Chancellorsville was considered a pyrrhic victory.