In the spring of 1863, Lee’s army defeated a Union force twice its size at Chancellorsville, Virginia, setting the stage for a Confederate thrust into Pennsylvania. Yet Lee’s decision to go on the offensive ultimately proved the Confederacy’s undoing. Even as draft riots erupted across the North in July 1863, the Union won two decisive military victories: at Gettysburg, Pennsylvania, and Vicksburg, Mississippi. These victories improved northern morale while devastating Confederate hopes. At the same time, the flood of African Americans, including former slaves, into the Union army transformed the very meaning of the war. In late 1864 and early 1865, the momentum favored the Union, and the South was forced to consider prospects for peace.