Major-General Henry W. Halleck was a studious West Point graduate, known as "Old Brains" in the Army, who General Scott had favored to replace him as general-in-chief. After President Lincoln appointed George B. McClellan to that post, he assigned Halleck to command the newly created Department of the Missouri, which replaced the old Department of the West and included operations in Missouri, Arkansas, Illinois, and western Kentucky. Halleck later did become general-in-chief in July 1862. (By John Osborne)