May 1863 -- The Battle of Chancellorsville/The Vicksburg Campaign

May 1863 -- The Battle of Chancellorsville/The Vicksburg Campaign,

On April 27, Union General Hooker crossed the Rappahannock River to attack General Lee's forces. Lee split his army, attacking a surprised Union army in three places and almost completely defeating them. Hooker withdrew across the Rappahannock River, giving the South a victory, but it was the Confederates' most costly victory in terms of casualties.

Union General Grant won several victories around Vicksburg, Mississippi, the fortified city considered essential to the Union's plans to regain control of the Mississippi River. On May 22, Grant began a siege of the city. After six weeks, Confederate General John Pemberton surrendered, giving up the city and 30,000 men. The capture of Port Hudson, Louisiana, shortly thereafter placed the entire Mississippi River in Union hands. The Confederacy was split in two.