After Van Dorn's defeat in the
Second Battle of Corinth on October 3–4, 1862, Confederate President
Jefferson Davis named
John C. Pemberton to lead the Department of Mississippi and East Louisiana and elevated him in rank to
Lieutenant General. The promotion made Pemberton superior to Van Dorn. On October 25, Grant assumed command of the Department of Tennessee and a week later he started the
Vicksburg campaign. By the end of October, Grant massed almost 50,000 Federal troops around Memphis and
Corinth, Mississippi. Grant planned to move south along the Mississippi Central Railroad with 40,000 troops. As he awaited approval from Union General-in-chief
Henry Halleck, Grant began concentrating five divisions at
Grand Junction, Tennessee. When Halleck endorsed the plan and told Grant that 20,000 additional reinforcements were forthcoming, Grant decided to wait for the new troops. However, he sent
James B. McPherson ahead with two divisions. Though a recent prisoner exchange swelled Van Dorn's strength to 24,000 troops, many of his soldiers were in poor health and the onset of cold weather increased the sick list. On November 9, Van Dorn withdrew from Holly Springs to a new defensive line behind the
Tallahatchie River. On December 1, Grant pressed forward again. A Federal force under
Alvin Peterson Hovey steamed down the
Mississippi River, landed at
Greenville, Mississippi, and marched inland toward the railroad. Van Dorn retreated behind the
Yalobusha River covering
Grenada, only north of
Vicksburg. At this time, Lieutenant Colonel John S. Griffiths of the
6th Texas Cavalry Regiment suggested raiding Grant's supply base at Holly Springs. Pemberton liked the idea and gave Van Dorn three brigades of cavalry to attempt the raid. He assigned Van Dorn's corps to
Dabney H. Maury. Meanwhile, President
Abraham Lincoln authorized
John A. McClernand to raise an army in the Midwestern states and lead it in an expedition against Vicksburg. McClernand's program was successful in recruiting large numbers of Union soldiers, which were forwarded to Memphis. The problem was that McClernand's expedition would be operating in a department commanded by Grant, a violation of the principle of
Unity of command. Furthermore, neither Grant nor General-in-chief
Henry Halleck liked McClernand. Halleck told Grant that all troops in the department were his to command. Grant ordered
William Tecumseh Sherman to take the soldiers at Memphis down the Mississippi River, enter the
Yazoo River, and assault Vicksburg from the north. On 18 December, Halleck telegraphed Grant that the troops at Memphis were to be organized into two corps, one under McClernand and one under Sherman. Grant notified McClernand at
Springfield, Illinois that he should go to Memphis to take charge of the expedition since he outranked everyone in the department except Grant. However, before the message was sent the telegraph lines were cut by Forrest's cavalry raid. Sherman left Memphis on December 20 with 32,000 troops. ==Van Dorn's Raid==