Vicksburg is the key remaining point of the Confederate defense of the Mississippi River.

The city's capture will yield the North control of the entire course of the river, and thus enable it to isolate those Confederate states that lay west of the river from those in the east.

The city is ideally suited for defensive purposes, however; as it is situated on high bluffs along the river and protected on the north by a maze of swampy bayous.

The Confederates' batteries on the bluffs can outgun any Union ships on the river.

A Union naval expedition in May and June 1862 uses ironclads in a failed attempt to subdue the Confederate batteries.