Though the outnumbered Confederate soldiers fought stubbornly, they were steadily pressed back during the day by Major General John A. McClernand's troops.

Finally, Grant ordered his army to march through swampy terrain on the west bank of the Mississippi River in an attempt to get south of Vicksburg.

The Confederate commander Lieutenant General John C. Pemberton was caught with his army scattered and could only oppose Grant with inferior forces at Port Gibson.

Grant's first foray with 40,000 soldiers came to grief when Major General Earl Van Dorn's cavalry wrecked his supply base in the Holly Springs Raid on December 20.

At the same time, a 32,000-man riverine expedition led by Major General William Tecumseh Sherman was repulsed at the Battle of Chickasaw Bayou on December 27–29.

Grant also tried to dig several canals to create a water-borne route west of the Mississippi River that would avoid the Vicksburg batteries; all were eventually abandoned.

[4] When newspaper editors and politicians demanded Grant's removal from command, President Abraham Lincoln replied, "I can't spare this man, he fights".

[5] Earlier in the campaign, Lieutenant Colonel James H. Wilson of Grant's staff suggested having Porter's fleet run past the Vicksburg batteries at night.

[10] The four XIII Corps divisions were led by Brigadier Generals Peter J. Osterhaus, Andrew Jackson Smith, Alvin P. Hovey, and Eugene Asa Carr.

The three XV Corps divisions were commanded by Brigadier Generals Frederick Steele, Francis Preston Blair Jr., and James M. Tuttle.

These were led by Bowen and Major Generals Martin Luther Smith, John Horace Forney, William Wing Loring, and Carter L. Stevenson.

Brushing aside a few hundred Confederates led by Major Isaac F. Harrison, Osterhaus' troops moved through swampy terrain along Roundaway Bayou and occupied New Carthage on April 6.

[17] Supply depots on the west bank of the Mississippi River were garrisoned by hastily recruited and trained African American soldiers led by white officers.

On the night of April 22, six unescorted transport vessels, each towing barges with 100,000 rations and other supplies, tried to pass the Vicksburg batteries.

On the morning of April 29, McClernand put his troops aboard transports at Hard Times Plantation and waited for Porter's gunboats to reduce the Confederate strongpoint.

Five hours later, the Battle of Grand Gulf ended in a Confederate victory when Porter's vessels withdrew after losing 19 killed and 56 wounded.

That night, Porter's gunboats and the transports ran the Grand Gulf batteries and joined McClernand's men at De Shroon's.

Colonel Benjamin H. Grierson's brigade of cavalry rode from La Grange, Tennessee, right across the state of Mississippi to Baton Rouge, Louisiana.

The third was the Battle of Snyder's Bluff from April 29 to May 1, when elements of Sherman's XV Corps mounted a demonstration north of Vicksburg in order to draw Pemberton's attention away from Grant's imminent crossing.

[20] Grant got information from a slave that a good road headed inland from Bruinsburg, which was 10 mi (16.1 km) downstream from Grand Gulf.

[21] On the morning of April 30, the Union soldiers embarked on transports at De Shroon's and crossed unopposed to the east bank of the Mississippi River at Bruinsburg.

Bowen expected to be reinforced by brigades led by Brigadier Generals Edward D. Tracy and William Edwin Baldwin, but they had not arrived at Grand Gulf by the morning of April 30.

Leading McClernand's column, Carr's division came into contact with Confederates near the Shaifer house about midnight and paused its march.

At 8:30 am, Tracy's small reinforcements arrived; the infantry regiment was sent to Green's right flank while the two guns from the Botetourt Virginia Artillery were positioned at the Foster farm.

[29] On the Rodney road, Carr's attack lost momentum and his two brigades became separated in the rough terrain, leaving a gap in the center of the line.

Brigadier General John E. Smith's brigade from Logan's division in McPherson's XVI Corps arrived and began pressing back Garrott's right flank.

As the combat intensified, Bowen began to fear that his opponents might turn his left flank, so he summoned two of Cockrell's Missouri regiments that had just arrived.

The original plan called for Grant to send the XIII Corps south to help Major General Nathaniel P. Banks reduce the Confederate stronghold at Port Hudson, Louisiana.

[38] When Grant found that Banks was not at Port Hudson, he decided to retain McClernand's corps and conduct his own campaign.

On May 6, even before Sherman's men joined him, Grant started his army marching northeast on the south side of the Big Black River with the aim of cutting the railroad between Vicksburg and Jackson.