The "Western Theater" refers to the area of military operations during the American Civil War that took place primarily in the western states and territories. This region included significant battles and campaigns in states like Tennessee, Kentucky, and Mississippi. Key battles such as the Battle of Shiloh and the Siege of Vicksburg were fought here, impacting the overall outcome of the war. In the Western Theater, the Union and Confederate armies engaged in various strategies to control key transportation routes and resources. The Union aimed to gain control of the Mississippi River, which was vital for supply lines. The successes and failures in this theater played a crucial role in shaping the course of the Civil War.