The autumn of 1862 saw the Confederacy launch its most ambitious series of attacks on the north. The main efforts were in Maryland (ending at Antietam) and Kentucky (ending at Perryville), but a third attack was launched towards western Tennessee from Mississippi.
The Union position in western Tennessee was vulnerable because General Halleck had broken up the army that had won at Shiloh and captured Corinth. Part of it had been sent east towards Chattanooga, although it moved too slowly to prevent the invasion of Kentucky. More of it was scattered around the vast areas captured after Grant’s series of victories.
By the autumn of 1862, Halleck had been promoted to General in chief and moved to Washington, leaving Grant in charge on the northern Mississippi. As was so often the case, the Confederate command was divided, between General Stirling Price, commanding between 15,000 and 17,000 men in the Army of the West, based at Tupelo, Mississippi (south east of Corinth), and General Earl Van Dorn, with 7,000 men of the Army of West Tennessee, based to the south west of Corinth.
The two Confederate forces were coming together with the intention of attacking Corinth. On 13 September, Price captured Iuka, twenty miles south east of Corinth. Demonstrating his normal aggressive spirit, Grant decided to attack Price before Van Dorn could reach him. His plan was somewhat ambitious. He had about the same number of men as Price, and decided to split his forces in two in an attempt to trap Price in Iuka. 8,000 men under General Ord were sent directly from Corinth towards Iuka, while a slightly larger force of 9,000 under General Rosecrans were sent to the south, to attack Price from his rear.
This plan did not work. Ord was in place late on 18 September, with orders to launch his attack when he heard the sound of Rosecrans’s guns. Unfortunately, Rosecrans did not get into position until the afternoon of 19 September, and by then Price was aware of his presence. He dispatched half of his troops in an attempt to deal with Rosecrans. This was when Ord should have launched his attack, but unusual weather conditions caused an acoustic shadow, preventing the sound of Rosecrans’s guns reaching Ord on the opposite side of Iuka.
Despite this, Rosecrans was able to hold off two hours of determined Confederate attacks, inflicting more casualties than he suffered (144 killed and 598 wounded, compared to 263 and 692 on the Confederate side). Unfortunately, he failed to block all of the roads south out of Iuka, and overnight Price was able to escape. From Iuka he headed west, and joined with Van Dorn. Their combined army now numbered around 21,000 men, strong enough to move on to launch an attack on Corinth (3-4 October 1862).