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.

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.

[11][12] 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.

[13][19][20][21] 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.

[22][23][24][25] 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.

[32][33] Major General Carter L. Stevenson, a subordinate of Pemberton's, was in command at Vicksburg, including the area between Haines Bluff and Grand Gulf.

[47][48] 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.

[47][48] 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.

[51] Sherman's men destroyed infrastructure in the city, including factories, warehouses, foundries, railroad tracks, telegraph wires and other property of military or economic value.

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.

[61] There, Pemberton ordered the garrisons at Haines Bluff, Walnut Hills and Warrenton to abandon their positions and move to the inner works at Vicksburg.

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.”[67][68] 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.

[79] He decided these lines were too strong to attack along the east side of the Big Black River, which some historians assert he did not want to do in any event.

[72][79] After learning of the surrender of Pemberton's army on July 4, 1863, on the same afternoon, Sherman ordered the units assigned for the expedition against Jackson to move to the Big Black River crossings.

[83] Although Johnston began to move back to Jackson on July 5, he left detachments to guard some of the crossings of the Big Black River.

[86][87] By late afternoon, Tuttle's men had secured the crest of a hill overlooking the river, pushed the Confederates away and established a camp more than three miles ahead on Bridgeport Road.

[87] Brigadier General William Sooy Smith's division of the IX Corp was the first to approach Birdsong's Ferry in the early morning of July 5.

[92] This meant that the Confederates would risk being trapped without sufficient supplies if they held out against an attacking force for any great length of time and could not remove stranded locomotives and railroad cars.

[93] The Confederates had poisoned wells and streams with dead animals as they progressed to Jackson, which forced the Union troops to haul drinking water from the Big Black River.

[93][99] Historian Jim Woodrick noted that numerous accounts by soldiers of both sides complained about the extreme heat and parched conditions.

[103] Hovey's and Lauman's divisions were placed last along the Terry Road and on Bailey Hill overlooking Lynch Creek east of the line of the New Orleans, Jackson and Great Northern Railroad entering the city from the south.

[108] Since Sherman did not want to make a frontal assault against strong resistance, on the night of July 10, he issued orders to the corps commanders to construct artillery positions and rifle pits as close as possible to the Confederate lines without taking needless casualties.

[4][112] Needing to conserve ammunition, on July 12 the Union artillery launched a heavy bombardment of the Confederate defenses but ceased firing in less than an hour.

[110] Pugh was reluctant to cross a field in front of the Confederate positions manned by the Washington Artillery and Brigadier General Daniel Weisiger Adams's brigade.

[117] Before the Union assault, Confederate soldiers had burned the Cooper House to give a clear field of fire in front of their fortifications.

[111] Sherman ordered Colonel Alexander Chambers brigade at Champion Hill to escort the wagon train after having received intelligence that Johnston was planning to send cavalry to intercept it.

[127] Sherman also ordered Brigadier General Charles Matthies to reinforce the garrison at Clinton to stop the Confederate cavalry's progress.

[130] On July 19, the Union force engaged with a Confederate cavalry rear guard under Brigadier General George Cosby, immediately losing a man killed.

"[137] A newspaper correspondent for the Memphis Appeal had been in Jackson during the siege and later reported that some fires had been started by Johnston's men before they left in order to destroy supplies.