Calvin continued to be assigned to Grant’s command. Grant had resolved to take control of the Mississippi, River from the Confederacy. To do so, President Lincoln and the Union Army and Navy were determined to take the Confederate stronghold at Vicksburg, Mississippi. The Vicksburg campaign started in December 1862 and lasted six months before the Union Army finally took the fortress. The campaign combined many important naval operations, troop maneuvers, failed initiatives, and was divided into two stages. The prize of capturing Vicksburg would ensure success and would divide the Confederacy into two eastern and western parts. At the opening of the campaign, Grant attempted to capture Vicksburg over land from the Northeast; however, Confederate Generals Nathan B. Forrest and Earl Van Dorn thwarted the Union Army advance by raiding Union supply lines.
