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Command Changes:

One of Grant's actions during the siege was to settle a lingering rivalry. On May 30, General McClernand wrote a self-adulatory note to his troops, claiming much of the credit for the soon-to-be victory. Grant had been waiting six months for him to slip, ever since they clashed early in the campaign, around the Battle of Arkansas Post. He had received permission to relieve McClernand in January 1863 but waited for an unequivocal provocation; McClernand was relieved on June 18. Grant so carefully prepared his action that McClernand was left without recourse. McClernand's XIII Corps was turned over to Maj. Gen. Edward Ord, who had recovered from an October 1862 wound sustained at Hatchie's Bridge. In May 1864, McClernand would be given a command in a remote area of Texas.

Another command change occurred on June 22. In addition to Pemberton in Vicksburg, Grant had to be aware of Confederate forces in his rear under the command of Joseph E. Johnston. He stationed one division in the vicinity of the Big Black River Bridge and another reconnoitered as far north as Mechanicsburg; both acted as covering forces. By June 10, the IX Corps, under Maj. Gen. John G. Parke, was transferred to Grant's command. This corps became the nucleus of a special task force whose mission was to prevent Johnston, who was gathering his forces at Canton, from interfering with the siege. Sherman was given command of this task force and Brig. Gen. Frederick Steele replaced him at XV Corps. Johnston eventually began moving to relieve Pemberton and reached the Big Black River on July 1, but he delayed a potentially difficult encounter with Sherman until it was too late for the Vicksburg garrison, and then fell back to Jackson. Sherman would pursue Johnston and recapture Jackson on July 17.
 

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