1862 after the Battle of Pea Ridge, and the state was then plagued by guerrilla warfare throughout 1862 and 1863. Price's Raid By the beginning of September 1864, events east of the Mississippi River, especially the Confederate defeat in the Atlanta campaign, gave Abraham Lincoln, who supported continuing the war, an edge in the 1864 United States Presidential Election over George B. McClellan, who promoted a war-ending armistice that would preserve slavery. Meanwhile, in the Trans-Mississippi Theater, the Confederates had defeated Union attackers in the Red River campaign in Louisiana in March through May. As events east of the Mississippi turned against the Confederates, General Edmund Kirby Smith, commander of the Trans-Mississippi Department, was ordered to transfer the infantry under his command to the fighting in the Eastern and Western Theaters. However, this proved to be impossible, as the Union Navy controlled the Mississippi River, preventing a large scale crossing. Despite having limited resources for an offensive, Smith decided that an attack designed to divert Union troops from the principal theaters of combat would have the same effect as the proposed transfer of troops. Major General Sterling Price and the Confederate Governor of Missouri Thomas Caute Reynolds suggested that an invasion of Missouri would be an effective offensive; Smith approved the plan and appointed Price to command the offensive. Price was a former governor of Missouri, had served in the Mexican-American War, and had commanded the Missouri State Guard in 1861 before entering Confederate service. Price expected that the campaign would create a popular uprising against Union control of Missouri, divert Union troops away from principal theaters of combat (many of the Union troops previously defending Missouri had been transferred out of the state, leaving the Missouri State Militia as the state's primary defensive force), and aid McClellan's chance of defeating Lincoln. On September 19, Price's column of about 12,000 to 13,000 men entered the state. Price soon learned that a Union force held Fort Davidson near Pilot Knob. Not wanting to leave a large Union force in the rear of his army, Price decided to attack the Union post. The attack, known as the Battle of Fort Davidson, occurred on September 27, and the Confederates were repulsed with heavy losses. While the fort's defenders retreated that night, Price decided to abandon plans to capture St. Louis as his troops had suffered at least 800 casualties and their morale had