History: American Civil War (1861-1865)

Western theater 1861–1863
While the Confederate forces had numerous successes in the Eastern Theater, they were defeated many times in the West. They were driven from Missouri early in the war as a result of the Battle of Pea Ridge. Leonidas Polk's invasion of Columbus, Kentucky ended Kentucky's policy of neutrality and turned that state against the Confederacy. Nashville and central Tennessee fell to the Union early in 1862, leading to attrition of local food supplies and livestock and a breakdown in social organization.
The Mississippi was opened to Union traffic to the southern border of Tennessee with the taking of Island No. 10 and New Madrid, Missouri, and then Memphis, Tennessee. In April 1862, the Union Navy captured New Orleans without a major fight, which allowed Union forces to begin moving up the Mississippi. Only the fortress city of Vicksburg, Mississippi, prevented Union control of the entire river.