After finally recovering enough for field command, Kimball was assigned to duty in the Western Theater, reporting in June 1863 to Corinth, Mississippi, where he assumed command of a division in the XVI Corps. His was one of three divisions in that corps that were ordered to Mississippi in to join the Siege of Vicksburg, although they arrived too late to participate in much of the actual fighting.
After recovering sufficiently to assume command, Kimball was assigned to duty in the Western Theater and reported to Corinth, Mississippi, where he took command of a division within the XVI Corps, which was one of three divisions sent to Mississippi to join the Siege of Vicksburg.