To do this it was necessary to take the Confederate stronghold at Vicksburg, Mississippi. By early 1862 this peaceful town had become one of the most strategically important spots in the entire Confederacy and would soon be the focus of a long and bloody campaign. The city was a great centre of trade, its port crowded with boats carrying all sorts of goods, it also served as an important transportation point for the Confederacy. Supplies, arms and troops from the southwestern states were gathered there and then transported eastward by rail.
From 1861, the Confederacy protected the Mississippi River by building fortifications at strategic points along it, but Federal forces eventually captured post after post after fighting their way southward from Illinois and northward from the Gulf of Mexico. By February 1862, the Union had captured Fort Donelson in northern Tennessee and broken the Confederate first line of defence for the Mississippi Valley.
In May 1862 Union forces tried to take Vicksburg using their ships, but the Confederates had strengthened their defences by setting up large batteries to block passage on the river. In June, several other attacks failed to get to Vicksburg by the River and it was realized by the Union high command that if Vicksburg was going to fall, it would be in the hands of a huge combined land and naval operation.
Earlier victories at Iuka and Corinth in Mississippi had led Major-General Ulysses S. Grant to be named commander of the Department of Tennessee in October 1862 and the very difficult task of clearing the Mississippi of rebel resistance and capturing Vicksburg was given to him. .
During the winter of 1862-1863, Grant conducted an unsuccessful series of amphibious operations to try to reduce the Vicksburg. In the spring of 1863, he developed a new plan for the taking of the city: a force led by Colonel Grierson moved trough the Mississippi countryside, drawing attention away from a naval operation attempting to slip past the city.