After encircling Confederate forces at Port Hudson, General Nathaniel Banks’ Union troops totaling approximately 13,000 in number on Tuesday, May 26, 1863 made a major assault on Port Hudson’s 4500 Confederates under the command of General Franklin Gardner.
In a disorganized attack which included some Negro troops, Union forces failed to breach the Confederate line, drawing close to the Confederate parapets before being repulsed but suffering some 1995 killed, wounded, or missing. The Confederates suffered approximately 235 casualties.
By late May 1863 United States naval forces were actively engaged against their Confederate foes. On the Mississippi River, on May 21, a Federal flotilla assaulted Confederate held, Yazoo City, Mississippi, forcing the evacuating Confederates to destroy their shops and naval yard, including two steamboats and a partially completed gunboat.
By late May 1863 both presidents of the North and South were busily corresponding with their subordinates in the field. Jefferson Davis wired General Braxton Bragg at Tullahoma, Tennessee, expressing concerns whether the Vicksburg garrison could be sustained and noting “The vital issue of holding the Mississippi at Vicksburg is dependent on the success of General Johnston in an attack on the investing force….Can you help him?”
On Friday, May 22, 1863, Ulysses Grant ordered a massive assault against Confederate held Vicksburg. Attacking on a three mile front with all available troops, approximately 45, 000 Federals charged the Confederate defenses, moving through deep, narrow ravines; the Confederates—behind a line of high breastworks protected by dirt and logs—rejected the Union attackers.
One breakthrough on the Confederate line was briefly successful before a counterattack closed the breach. Grant’s Federals suffered 3199 casualties, with less than 500 Confederate defenders dead or wounded.
With Ulysses Grant’s Federals at the gates of Vicksburg, on May 21, 1863 Union forces under General Nathaniel Banks moved out of Baton Rouge and Alexandria, Louisiana and headed toward Confederate held Port Hudson on the Mississippi River.
Except for Vicksburg, Port Hudson was the remaining Confederate defense on the Mississippi River. Like Vicksburg, it had to be held at all costs to prevent the Confederacy from being bisected at the Mississippi River.
On Tuesday, May 19, 1863 with the envelopment of Confederate held Vicksburg complete, Ulysses Grant ordered the first, direct assault against the city’s substantial defenses. With William Tecumseh Sherman’s corps to the north or right, James McPherson’s corps in the center, and John McClernand’s corps on the left, thousands of Union troops confronted Vicksburg.
On Monday, May 18, 1863 Ulysses Grant’s Federal army, triumphant at Champion Hill and the Big Black River, began to envelope Vicksburg. John Pemberton was ordered by General Joseph Johnston to evacuate Vicksburg, but knowing that President Jefferson Davis wished to have the city defended, Pemberton with the concurrence of his subordinate officers decided to stay.
Pursuing John Pemberton’s retreating Confederates from Champion Hill, on May 17, 1863, Federal forces attacked Pemberton’s Confederates on the east bank of the Big Black River. Attacking through waist deep water, Union forces overran the Confederates’ breastworks of cotton bales and an abatis of felled trees to the front, forcing the Confederates in confusion and panic to withdraw across the river.
Following the Union occupation of Jackson, Mississippi, General Joseph Johnston, overall Confederate commander in Mississippi, ordered General John Pemberton at Vicksburg to attack the Federals at Clinton.
Pemberton believed that Johnston’s plan was too dangerous and decided instead to attack the Union supply trains moving from Grand Gulf to Raymond. On May 16, 1863 Pemberton’s forces approached Champion Hill when he received another order from Johnston, repeating his former instructions.
On Wednesday, May 13, 1863 Abraham Lincoln in response to a letter by Joseph Hooker, in which the general cited problems within his Union Army of the Potomac causing delayed operations since the debacle at Chancellorsville, noted that he would not restrain Hooker from renewing offensive actions but warned his general that he had indications that “some of your corps and Division Commanders are not giving you their entire confidence.”