In spring 1863, amid turmoil on the home front, General Robert E. Lee’s army defeated a Union force twice its size at Chancellorsville, Virginia. The victory set the stage for a Confederate thrust into Pennsylvania, but Lee’s decision to go on the offensive proved the Confederacy’s undoing. In July 1863 the Union won two decisive military victories: at Gettysburg, Pennsylvania, and Vicksburg, Mississippi. At the same time, the flood of African Americans, including former slaves, into the Union army transformed the very meaning of the war. By 1864, with the momentum favoring the Union, General Ulysses S. Grant implemented policies of hard war that forced the Confederacy to consider surrender.