Why were the siege of Vicksburg and the battle of Gettysburg crucial to the outcome of the war?
Vicksburg and Gettysburg were two crucial Union victories that were made even more important because they occurred just days apart in July of 1863. Vicksburg, Mississippi occupied bluff atop a bend in the river, and as long as it was under Confederate control, the Union could not fully control navigation on the river, which had been a major strategic objective from the beginning of the war. Vicksburg fell on July 4, 1863 after a siege of almost two months. The loss was a crippling one for the Confederacy, which saw its western department severed from the East. It also resulted in the appointment of Ulysses S. Grant, the victorious commander at Vicksburg, to command of all Union forces.
One day before Vicksburg's surrender, the Confederate Army of Northern Virginia had been halted in its invasion of Pennsylvania at the battle of Gettysburg. Lee's forces, which had achieved a series of stunning victories, were repulsed after a series of attempts, over three bloody days, to smash through the Union lines outside the small town in the Pennsylvania countryside. The battle marked the "high-water mark" for the Confederacy, which would engage in strategically defensive operations only from that point forward. Taken together, the two battles are viewed by historians as the crucial turning points of the war in the western and eastern theaters, respectively.