The Army of the Tennessee was a major Union army during the American Civil War, established in 1862. It played a crucial role in several key battles, including the Battle of Shiloh and the Siege of Vicksburg. Commanded by notable leaders such as Ulysses S. Grant, the army was instrumental in the Union's efforts to gain control of the Mississippi River. This army was part of the larger Western Theater of the war, which focused on battles in the southern and western states. The Army of the Tennessee was known for its mobility and effectiveness, contributing significantly to the Union's overall victory in the conflict.