This department existed in two separate periods. The first was created on August 15, 1861. It was geographically defined by the states of Kentucky and Tennessee. Headquarters were originally in Cincinnati, Ohio, and moved to Louisville, Kentucky, on September 7, 1861. The fifteen mile area of Kentucky surrounding Cincinnati was transferred to the Department of the Ohio on September 19, 1861. Union forces directing operations in the vicinity of the Ohio, Cumberland, and Ohio River junctures and at the intersection of Ohio and Mississippi Rivers became part of the Western Department. The department was divided on November 9, 1861. The area of Kentucky west of the Cumberland River transferred to the Department of the Missouri and the area of Kentucky east of the Cumberland River and the state of Tennessee were transferred to the Department of the Ohio. Commander(s): Robert Anderson and William T. Sherman. The second was created on October 24, 1862. It was geographically defined by the portion of Tennessee east of the Tennessee River, excluding Fort Henry, Fort Donelson, and Cumberland Gap, and the portions of Alabama and Georgia controlled by Federal forces. Fort Henry, Fort Donelson, and Fort Heiman were transferred into this department on January 25, 1863. The department became a part of the Military Division of the Mississippi on October 16, 1863, along with the Departments of the Tennessee and the Ohio. The Department of the Ohio merged into this department on January 17, 1865. This added the state of Kentucky, that part of Tennessee east of the Tennessee River, and the parts of Alabama, Georgia, and Mississippi under the control of Federal forces. The Department of Kentucky was created on February 10, 1865, removing the state of Kentucky from the department. Also, the entire state of Tennessee was reunited under one department, following the transfer of state of Tennessee west of the Tennessee River from the Department of the Mississippi. The department added northern Mississippi on May 27, 1865. The Department of the Cumberland was disbanded on June 27, 1865, the entire state of Tennessee becoming the Department of Tennessee. The Military Division of the Tennessee was created on the same day, inclusive of the departments of Kentucky, Tennessee, Georgia, and Alabama. Commander(s): Williams S. Rosecrans and George H. Thomas.