By early 1863 the Confederates only controlled a stretch of the Mississippi River between Vicksburg, Mississippi, and Port Hudson, Louisiana-- Vicksburg was the more important of the strongholds. Vast quantities of supplies passed through the city on its way to the main Confederate armies. Capture of the city was vital to the Union war effort. The responsibility for capturing it was given to General Ulysses S. Grant who, despite a series of setbacks, developed a bold combined arms operation to achieve his task.
The campaign began when Rear Admiral David Dixon Porter “ran” his ships past the Confederate guns at Vicksburg while Grant marched his army south along the western bank of the Mississippi. The two forces were to unite at Grand Gulf where Porter would ferry the army across the river. This changed when Confederate fortifications were spotted upon the bluffs there, and Grant shifted the crossing further south to Bruinsburg.
Once his army crossed the river, Grant pushed inland, driving Confederate defenders back in sharp engagements at Port Gibson and Raymond on May 1 and 12, respectively. Following Raymond, Grant’s army was between General John C. Pemberton’s force near Vicksburg and an army of reinforcements under General Joseph Johnston at Jackson.
Grant sent one-third of his army under General William T. Sherman to take Jackson while he moved west towards Vicksburg with the rest. Pemberton moved to engage him and the two armies met at the Battle of Champion Hill on May 16. Grant forced Pemberton to retreat into the defenses of Vicksburg and besieged the city for nearly two months before Pemberton surrendered on July 4. Five days later, Port Hudson fell and the Mississippi River was firmly under Federal control.