On May 9, Gen. Johnston received a dispatch from the Confederate Secretary of War directing him to "proceed at once to Mississippi and take chief command of the forces in the field." As he arrived in Jackson on May 13, from Middle Tennessee, he learned that two army corps from the Union Army of the Tennessee—the XV, under Maj. Gen. William Tecumseh Sherman, and the XVII, under Maj. Gen. James B. McPherson—were advancing on Jackson, intending to cut the city and the railroads off from Vicksburg, Mississippi which was a major port on the Mississippi River. These corps, under the overall command of Grant, had crossed the Mississippi River south of Vicksburg and driven northeast toward Jackson. The railroad connections were to be cut to isolate the Vicksburg garrison. And if the Confederate troops in Jackson were defeated, they would be unable to threaten Grant's flank or rear during his eventual assault on Vicksburg.
Battle
Johnston consulted with the local commander, Brig. Gen. John Gregg, and learned that only about 6,000 troops were available to defend the town. Johnston ordered the evacuation of Jackson, but Gregg was to defend Jackson until the evacuation was completed. By 10 a.m., both Union army corps were near Jackson and had engaged the enemy. Rain, Confederate resistance, and poor defenses prevented heavy fighting until around 11 a.m., when Union forces attacked in numbers and slowly but surely pushed the enemy back. In mid-afternoon, Johnston informed Gregg that the evacuation was complete and that he should disengage and follow.
Aftermath
Soon after, Union troops entered Jackson and had a celebration in the Bowman House, hosted by Grant, who had been traveling with Sherman's corps. They then burned part of the town and cut the railroad connections with Vicksburg. Johnston's evacuation of Jackson was premature because he could, by late on May 14, have had 11,000 troops at his disposal and by the morning ofMay 15, another 4,000. The fall of the former Mississippi state capital was a blow to Confederate morale. General Sherman appointed Brig. Gen. Joseph A. Mower to the position of military governor of Jackson and ordered him to destroy all facilities that could benefit the war effort. With the discovery of a large supply of rum, it was impossible for Mower's Brigade to keep order among the mass of soldiers and camp followers, and many acts of pillage took place. Grant left Jackson on the afternoon of May 15 and proceeded to Clinton, Mississippi. On the morning of May 16 he sent orders for Sherman to move out of Jackson as soon as the destruction was complete. Sherman marched almost immediately, clearing the city by 10 a.m.. By nightfall on May 16, Sherman's corps reached Bolton, Mississippi, and the Confederacy had reoccupied what remained of Jackson. Jackson had been destroyed as a transportation center and the war industries were crushed. But more importantly the Confederate concentration of men and materials aimed at saving Vicksburg were scattered. Sherman would later lead an expedition against Jackson following the fall of Vicksburg to clear Johnston's relief force from the area.
