The tide of the war changes decisively against the South as Grant takes Vicksburg. Meanwhile in the East, Robert E. Lee's second invasion of the North is thrown back during three bloody days at Gettysburg. In early 1864, Grant takes supreme command of all Union armies and plans a grand offensive against the Confederates on all fronts. Starting in May, Grant unleashes his campaign against Robert E. Lee, and the two sides suffer tens of thousands of casualties at Wilderness, Spotslyvania and Cold Harbor.