Campaign of Vicksburg, major siege of the American Civil War, consisting of military campaigns in 1862 and 1863 that ended with the capture of the city of Vicksburg, Mississippi, by Union troops on July 4, 1863.

Vicksburg, perched on a steep bluff along the eastern bank of the Mississippi River, was one of the main Southern strongholds along the river. It was therefore of strategic importance to both the North and South. In February 1862 the Union captured Fort Donelson in northern Tennessee, which broke the Confederate first line of defense for the Mississippi Valley. Vicksburg then remained the one serious obstacle to federal command of the Mississippi River. Union control of the Mississippi meant the Confederacy would be split in two.

In May 1862 Union forces made an unsuccessful attempt to take the city by means of a naval expedition. The Confederates strengthened their defenses, setting up extensive batteries to obstruct passage on the river. On June 27 a Union fleet under Admiral David G. Farragut appeared below the city; the next day two frigates and six gunboats attempted to run the Confederate river fortifications. The attack failed, as did several subsequent maneuvers to bypass Vicksburg by river.

In December 1862 the Union General Ulysses S. Grant proposed moving from a base in Holly Springs, Mississippi against the town of Grenada. The goal was to cut the Confederate line of communications and draw General John C. Pemberton, the Confederate commander of Vicksburg, from his stronghold. Meanwhile, an army under Union General William T. Sherman was to be convoyed downriver by a fleet commanded by the Union naval officer David D. Porter; Sherman would then seize the city in the absence of a majority of its defenders. These plans, however, were upset by a Confederate raid on Holly Springs, which halted Grant’s advance. Sherman, after a successful landing, found the countryside virtually impassable because of swampy land. Nevertheless he engaged in bloody but futile attacks in late December. Soon after the Union armies retreated north of Vicksburg.

In April 1863 Grant made a bold decision. Ignoring the advice of Sherman and others that the Union forces retreat to Memphis, Tennessee, Grant decided to attack Vicksburg from the east. First he sent Union boats under Porter down the Mississippi River to try to run the Confederate blockades at Vicksburg; a number of the boats made it through successfully. Next he marched his troops down the west side of the Mississippi River in Louisiana; they marched and floated some 48 km (30 mi) south, then used the boats to cross the river from Hard Times, Louisiana to Bruinsburg, Mississippi on April 30, 1863. At the same time, troops under Sherman moved north of Vicksburg and exchanged fire with the Confederates to create a diversion during the river crossing.

Once on the east side of the river, Union forces took the towns of Port Gibson and Grand Gulf. They then marched northeast, cutting their own supply lines and heading deep into enemy territory. By this time, Sherman had come south to reunite with Grant, and there were more than 40,000 Union soldiers below Vicksburg. Sensing Grant’s intentions too late, the Confederate General Joseph E. Johnston tried to gather forces together to march toward Vicksburg from his base in Jackson, but Grant’s army arrived at Jackson first and defeated Johnston. Grant then repulsed Pemberton at Champion’s Hill on May 16 and attacked Vicksburg on May 19. Two assaults on the fortress failed and siege operations were begun; these lasted for almost six weeks. On July 4, 1863, the Confederate defenders surrendered the city along with more than 30,000 soldiers. The soldiers were originally taken as prisoners of war, but they were later paroled, taking an oath not to bear arms again until there was a formal exchange of prisoners.

The Union capture of Vicksburg was one of the most important Northern victories of the war. It gave the North control of the Mississippi River, allowing them passage straight through the Confederacy. With this passage, they were able to move supplies and men along the river. In addition, the capture freed Grant’s armies and allowed the North to use them for other battles, such as fighting the war in Virginia.