Grant's Army of the Tennessee was besieging the Army of Vicksburg.
The Confederates lost about 9,000 in battle, against 10,000 Union men.
In May and June of 1863, Maj. Gen. Ulysses S. Grant's armies converged on Vicksburg, investing the city and entrapping a Confederate army under Lt. Gen. John Pemberton. On July 4, Vicksburg surrendered after prolonged siege operations. This was the culmination of one of the most brilliant military campaigns of the war.
With the loss of Pemberton's army and this vital stronghold on the Mississippi, the Confederacy was effectively split in half. Grant's successes in the West boosted his reputation, leading ultimately to his appointment as General-in-Chief of the Union armies.