Military campaign during the American Civil War
The Jackson expedition, preceding and related to the siege of Jackson immediately followed the Confederate surrender of Vicksburg, Mississippi on July 4, 1863, to Union Army Major General Ulysses S. Grant commanding the Union Army of the Tennessee. The Confederate Army of Mississippi at Vicksburg, under the command of Lieutenant General John C. Pemberton, had been isolated in the Vicksburg defenses by Grant's forces since May 18, 1863. The Confederates were under constant artillery bombardment, had to fight off a series of Union Army attacks and could not receive supplies of food and ammunition during the siege. 
On May 14, in line with Grant's plan to eliminate other Confederate forces in the area before marching on Vicksburg, a Union force of two corps under Major General William T. Sherman and Major General James B. McPherson drove the Confederates out of Jackson, Mississippi northward toward Canton, Mississippi, about 25 miles away. After this brief Battle of Jackson, Mississippi, McPherson's corps left immediately to rejoin Grant's force while Sherman's corps remained for another day to damage or destroy fortifications, railroad facilities and buildings and supplies of military value. 
Johnston returned to Jackson on May 20. Although reinforcements were already arriving, he thought he needed time to receive more reinforcements before attempting to relieve Vicksburg. He tried unsuccessfully to convince Pemberton to abandon Vicksburg and to combine with his force to confront the Union Army while they had similar numbers of men. Johnston's delayed and cautious effort to relieve Pemberton's forces at Vicksburg in the final days of the siege was too late to attempt to lift the siege. Johnston already had concluded that his force was too small to try to relieve Pemberton's army without also being trapped by the Union Army. 
When the siege of Vicksburg ended, Johnston's relief force, called by him the “Army of Relief”, was at the Big Black River near Vicksburg. Grant was concerned about a possible attack by Johnston's force against his army and a Confederate attempt to retake Vicksburg. Before Johnston brought his army close to Vicksburg, at Grant's order, Sherman had already deployed the recently arrived IX Corps under Major General John G. Parke and other assigned divisions in an exterior line to defend against attack from outside Vicksburg by another Confederate force. On July 4, the date of the Vicksburg surrender, Grant ordered Sherman to lead an expedition to clear Johnston's forces from the Vicksburg area and to recapture the state capital and railroad center at Jackson. Sherman's corps combined with all or part of three other corps pushed Johnston's force back to Jackson by July 10 under grueling summer conditions. After a few engagements during a brief siege of Jackson, on July 16, Johnston's concern about being trapped and having to surrender his army, caused him to abandoned the city. Jackson's military and commercial facilities then were further destroyed by the Union forces. This Union victory helped ensure that Vicksburg, the Mississippi River and Jackson, would remain in the Union's possession for the rest of the war.
Background.
In late 1862, the Confederate stronghold at Vicksburg, Mississippi was the last major fortress on the last section of the Mississippi controlled by the Confederacy. After the Battle of Arkansas Post (1863) on January 11, 1863, the Confederates controlled only a 240-mile (386.2-km) stretch of the river from Vicksburg to Port Hudson, Louisiana. The Confederates remained able to block Union shipping over that section of the river and to allow communications and supply between Confederate states east and west of the river, especially at the main transfer point at Vicksburg.
Several attempts to capture Vicksburg overland from Tennessee in December 1862 and by attacking the city from the impassable bayous across the river in Louisiana in early 1863 failed. Grant then devised a plan for a second campaign to capture the city by crossing the Mississippi south of Vicksburg and approaching the city from the south.
Vicksburg Campaign.
Start of the campaign.
On April 15 and April 22, 1863, Union gunboats, transports and supply vessels ran past the Confederate artillery batteries at Vicksburg from north to south with the loss of one gunboat, one transport with hospital stores and six barges with coal. Grant could now move his army across the river to Mississippi but the Union naval force could not silence all Confederate artillery batteries at Grand Gulf. Grant and Acting Rear Admiral David Dixon Porter decided to move farther south and, with advice from an escaped slave, found a suitable landing at Bruinsburg, Mississippi. Grant's forces successfully crossed the river without Confederate opposition on the night of April 30, 1863 and into the day on May 1. 
At the Battle of Port Gibson on May 1, Union forces defeated the heavily outnumbered Confederates under Brigadier General John S. Bowen, causing the abandonment of the Port Gibson defenses and securing the Union position east of the river. The Confederate defenses on the Mississippi at Grand Gulf, Mississippi became untenable with Bowen's defeat and the Confederates also abandoned that position on May 2.
Pemberton commanded the Army of Tennessee from Jackson, Mississippi, 44 miles by railroad west of Vicksburg, from the first week of October 1862 until May 1, 1863. Major General Carter L. Stevenson, a subordinate of Pemberton's, was in command at Vicksburg, including the area between Haines Bluff and Grand Gulf. After Grant's army successfully crossed the Mississippi River from Louisiana at Bruinsburg, Mississippi on April 30-May 1, Pemberton moved his headquarters and three divisions from Jackson to Vicksburg. On May 9, the remaining Confederate garrison of about 6,000 men at Vicksburg came under the direct command of General Joseph E. Johnston, who was in charge of the Confederate Department of the West. 
Johnston was ordered to take command of the Mississippi defenses on May 9, but was not given full authority over Pemberton, who, along with General Braxton Bragg and Trans-Mississippi commander Theophilus Holmes, reported directly to Confederate States President Jefferson Davis. Johnston arrived at Jackson on May 13, 1863 to take charge of troops there and to carry out his orders to advise Pemberton. Johnston could only try to persuade Pemberton to act, including to accept Johnston's plan to combine forces to confront Grant in the field.
Grant decided not to take the narrow and rough direct route to Vicksburg but to approach from the west after moving northeast to destroy a portion of the Southern Railroad of Mississippi to prevent supplies and reinforcements moving from Jackson to Vicksburg. Grant also wanted to defeat Pemberton's forces outside the Vicksburg defenses, if possible. On May 12, Union Major General McPherson's XVII Corps defeated a detached Confederate brigade near Jackson at the Battle of Raymond, despite some mismanagement of the battle. McPherson did not pursue Brigadier General John Gregg's brigade back to Jackson.
Battle of Jackson.
Grant was unsure of the size of the Confederate force at Jackson. He decided to eliminate any threat to his army from Confederate forces at Jackson before moving against Pemberton's force. Three divisions led by Pemberton had taken the field to intercept Grant's supply line. Grant ordered Sherman's XV Corps to attack Jackson from the southwest and McPherson's XVII Corps to attack from the northwest. Johnston decided as soon as he arrived that he was too late to hold the city, if not to rescue Pemberton and retain Vicksburg. Without waiting for the imminent arrival of reinforcements, Johnston decided to abandon Jackson with the garrison of 6,000 troops and to regroup at Canton, Mississippi, about 25 miles to the north.
Except for a brief stand by a Confederate rearguard under Brigadier General John Gregg, the Union attack quickly drove Johnston and the remaining garrison from the city at the Battle of Jackson, Mississippi on May 14. The city was surrendered by militia artillerymen and armed civilians. Since Pemberton was moving to the southeast, Johnston's move northward toward Canton took his force farther from Pemberton's force. Grant left Sherman's corps in Jackson with orders to destroy anything of military value. Sherman's men destroyed infrastructure in the city, including factories, warehouses, foundries, railroad tracks, telegraph wires and other property of military or economic value. Sherman's corps left Jackson on May 16, 1863.
Battles of Champion Hill and Big Black River Bridge.
On May 13, 1863, Pemberton led a force of 18,500 men in three divisions from Vicksburg to a point halfway to Jackson. Grant expected to find Johnston's force near Bolton, Mississippi along the Southern Railroad of Mississippi and decided to move his army in that direction. Instead of moving toward Johnston's force, Grant learned that Pemberton was heading toward Bolton to try to cut what he thought was the Union supply line. Pemberton had insufficient supplies and on May 15, he had to wait to move forward for rations and ammunition to be brought up from Vicksburg. Then, because of a bridge washout, Pemberton's men had to cross Baker's Creek upstream and camp east of the creek at Champion Hill. Despite the approach of Grant's entire force early on May 16, Pemberton was unaware of the full threat. The Confederates were soundly defeated at the Battle of Champion Hill, 18 miles west of Jackson, and retreated to Vicksburg. Following the Battle of Champion Hill, Sherman's corps also rejoined Grant's force. Grant's army then defeated a Confederate rear guard of about 5,000 troops at the Battle of Big Black River Bridge on May 17, 1863.
Start of the Vicksburg siege.
The Confederates withdrew into the Vicksburg defenses on May 17, 1863. There, Pemberton ordered the garrisons at Haines Bluff, Walnut Hills and Warrenton to abandon their positions and move to the inner works at Vicksburg. On May 18, 1863, Pemberton received an instruction from Johnston to abandon the city and join his forces at Canton but Pemberton refused to do so, stating that he would hold the city. Jefferson Davis had declared that Vicksburg and Port Hudson should be held.
After costly Union frontal assaults at Vicksburg failed on May 19, 1863, and May 22, 1863, Union siege operations at Vicksburg began. Grant formally ordered the operations on May 25. Grant's Special Order Number 140, May 25, 1863, formally initiating siege operations, read: “Corps commanders will immediately commence the work of reducing the enemy by regular approaches. It is desirable that no more loss of life shall be sustained in the reduction of Vicksburg and the capture of the garrison.”
End of Vicksburg siege.
On June 22, 1863, Grant received an erroneous report that Johnston had crossed the Big Black River and was preparing to attack the Union forces. He also heard that some Union cavalry troopers were driven back by a Confederate raid at Birdsong's Ferry. Concerned with the possibility that Johnston would try to begin offensive operations from behind the Union positions, Grant ordered Sherman to expand a defensive line facing east from Snyder's Bluff overlooking the Yazoo River to the railroad bridge over the Big Black River west of Messinger's Ferry.
On June 25, 1863, Grant tried to bring the siege to a close by ordering mine explosions under the Confederate Third Louisiana Redan and a major Union attack on the Confederate positions after the explosion. The assault on the Confederate line failed to take the position. On July 1, another mine explosion was set off under the redan but it was not followed by an assault because the explosion was set off mainly to show the Confederates that their position was hopeless.
Despite receiving reinforcements bringing his total force to about 32,000 men by June 1, Johnston made no move to relieve Vicksburg until the end of June. He later would report to Jefferson Davis that he had received men but not the supplies, artillery, horses and wagons needed to move them. While Johnston delayed, Grant was being reinforced continuously through June. 
Having not taken advantage of the small Confederate numerical superiority of Pemberton and his own combined forces in the first week of June, Johnston did not issue orders to move in force to the Big Black River until June 28. The Confederates did not approach the Union lines near Vicksburg until July 1. Instead of scouting approaches to the city when he finally arrived near the Union lines, Johnston examined reports about the roads, fords and Union positions between Jackson and Vicksburg. He found that the Union exterior line established by Sherman extended farther