From mid-October 1862, Maj. Gen. Ulysses S. Grant made several attempts to take Vicksburg. Following failures in the 1st Vicksburg Campaign, the Battle of Chickasaw Bluffs, the Yazoo Pass Expedition, and Steele's Bayou Expedition, in the spring of 1863 he prepared to cross his troops from the west bank of the Mississippi River to a point south of Vicksburg and drive against the city from the south and east. Commanding Confederate batteries at Port Hudson, Louisiana, farther south prevented the transportation of waterborne supply and any communicatio from Union forces in Baton Rouge and New Orleans. Naval support for his campaign would have to come from Rear Adm. David D. Porter's fleet north of Vicksburg. Running past the powerful Vicksburg batteries, Porter's vessels, once south of the city, could ferry Federals to the east bank. There, infantry would face 2 Confederate forces, one under Lt. Gen. John C. Pemberton at Vicksburg and the another around Jackson, Mississippi, soon to be commanded by gen. Joseph E. Johnston.
In January, Grant organized his force into the XIII Corps under Maj. Gen. John A. McClernand, the XV Corps under Maj. Gen. William T. Sherman, the XVI Corps under Maj. Gen. Stephen A. Hurlbut, and the XVII Corps under Maj. Gen. James B. McPherson. Simultaneous with Grant's Vicksburg offensive, Maj. Gen. Nathaniel P. Banks began his manuevering along the Red River in Louisiana. Hurlbut's corps was subsequently transferred to New Orleans. With his 3 remaining corps, Grant began operations late in March. On March 29-30th, McClernand's and McPherson's men, at Miliken's Bend and Lake Providence, northwest of Vicksburg, began working their way south, building a military road to New Carthage, Louisiana, prepatory to a move south to Hard Times, Louisiana, a village opposite Bruinsburg, Mississippi.
On the night of April 16th at Grant's request, Porter took 12 vessels south past the Vicksburg batteries, losing i to Confederate fire. On the 17th, Grierson's Raid began. Led by Brig. Gen. Benjamin H. Grierson, Union cavalry left LaGrange, Tennessee for 16 days riding through central Mississippi to Baton Rouge, pulling away large units from Vicksburg's defense to pursue them. Porter, encouraged by light losses on his 1st try, ran a large supply flotilla past the Vicksburg batteries the night of the 22nd. Sherman's troops, many at work on a canal project at Duckport, abandoned this work, joined in a last action along the Yazoo River, northeast of Vicksburg, and on the 29-30th, made a demonstration against confederate works at Haynes' Bluff and Drumgould's Bluffs, diverting more of Pemberton's force Also on the 29th, as McClernand's and McPherson's troops gathered near Hard Times, Porter's fleet assailed Confederate batteries at Grand Gulf, 33 miles southwest of Vicksburg, testing the Grand Gulf area as a landing site for Union troops. Though Porter found the guns there too strong, he had succeeded in further diverting Pemberton in Vickdburg.
Grant had originally determined that Rodney, Mississippi would be the starting point of his invasion, but took the advice of a local slave and picked Bruinsburg instead. McClernand's and McPherson's corps were ferried east across the Mississippi from Hard Times on the 30th. That day, Grant sent word north for Sherman to follow McPherson's route south and join him.
On May 1st, the Union invasion force engaged the Confederates in the Battle of Port Gibson. Pemberton had just over 40,000 men assigned to the Vicksburg region. Since they were scattered throughout the area, chasing Grierson and wary of Sherman, few of them could be brought to bear against Grant on short notice. Defeated at Port gibson, Pemberton's confusion, pushed northeast. Sherman's corps joined him on May 8th and 12th, the engagement at raymond was fought. Johnston took personal command of Confederates at jackson, 15 miles northeast of Raymond on the 13th. On the 14th, Federals quickly won an engagement at Jackson, cut off Johnston from Pemberton, and ensured the latter's isolation for the rest of the campaign. In 2 weeks, Grant's force had come well over 130 miles northeast from their Bruinsburg landing site.
Ordering Sherman to destroy Jackson's heavy industry and rail facilities, Grant turned west, roughly following the Southern Mississippi Railroad to Bolton, and on the 16th, fought the climatic combat of his field campaign, the Battle of Champion's hill. With the largest force, he had yet gathered to oppose Grant, Pemberton nevertheless took a beating there and pulled his army into the defenses of Vicksburg. In a delaying battle at Big Black River Bridge on the 17th, Confederates crossed the Big Black, destroying their river crossings behind them. Undeterred, Federals threw up their own bridges and continued pursuit the next day.
Approaching from the east and northeast, McClernand's, McPherson's, and Sherman's corps neared the Vicksburg defenses on the 18th, Sherman's veering north to take the hills overlooking the Yazoo River. Possession of these heights assured Grant's reinforcement and supply from the North. The next day, Federals made the failed assault on Vicksburg. The 2nd assault on the 22nd, was a disaster for Union forces, showed the strength of the miles of Confederate works arching east around the city, and convinced Grant that pemberton could only be defeated in a protracted seige.
The seige of Vicksburg began with the repulse of the assault on the 22nd, and it lasted until July 4th. As the seige progressed, Pemberton's 20,000-man garrison was reduced by disease and starvation, and the city's residents were forced to seek the refuge of caves and bombproofs in the surrounding hillsides. Hunger and daily bombardments by Grant's forces and Porter's gunboats compelled Pemberton to ask for surrender terms on July 3rd. Grant offered none, but on the garrison's capitulation immediately paroled the bulk of the force. Many of these same men would later oppose him at Chattanooga.
Pemberton's surrender ended the 2nd Vicksburg Campaign. During the seige, to the east Johnston had raised a 31,000 man force in the Jackson area. On the 4th, as Confederates were being paroled, Sherman moved his force to oppose this new threat. Sherman's march would result in the Seige of Jackson.
Grant's bold plan for the conduct of the Vicksburg Campaign was carried out to perfection. While a corps under Maj. Gem. William T. Sherman demonstrated north or Vicksburg late in March, the other two corps, under Maj. Gens. John A. McClernand and James B. McPherson, made a wide swing southward on the west side of the Mississippi and then back to the river at Bruinsburg, about 30 miles below Vicksburg. Sherman's corps followed the same route, Joining Grant early in May. Meanwhile, on the night of 16-17 April, Flag Officer David D. Porter sailed his river fleet down the river, survived a heavy bombardment as he passed Vicksburg, and, beginning on 30 April, ferried Grant's troops across the river.
Vicksburg was defended by some 30,000 Confederates under Lt. Gen. John G. Pemberton. Other Confederate forces under J. E. Johnston were concentrated in the vicinity of Jackson, Miss., 40 miles east of Vicksburg. Grant's plan was to interpose his army between Pemberton and Johnston and then to fend off Johnston while taking Vicksburg. Therefore he fought his way northeastward, took Raymond on 12 May, and drove Confederate forces out of Jackson on 14 May. Then, while Sherman's corps contained Johnston, Grant advanced on Vicksburg, winning engagements at Champion's Hill (16 May) and Black River Bridge (17 May), and drove Pemberton's forces into the city. Assaults on 18 and 22 May failed to breach Vicksburg 's defenses. The Federals thereupon settled down to a siege, which ended with Pemberton's surrender on 4 July 1863. Pemberton's 29,396 officers and enlisted men were granted parole under the terms of the surrender. Federal losses during the campaign were about 3,500; Confederate losses were more than 8,000 killed, wounded, and missing.
While Grant was laying siege to Vicksburg, a 15,000-man force under Banks (who had replaced Butler) moved north from New Orleans and attacked Port Hudson, which fell on 8 July 1863. The whole Mississippi River thereby came under Union control and the Confederacy had been cut in two.