Peter Joseph Osterhaus was a German-American Union Army general in the American Civil War and later served as a diplomat.

The Army of the Tennessee was a Union army in the Western Theater of the American Civil War, named for the Tennessee River. A 2005 study of the army states that it "was present at most of the great battles that became turning points of the war—Fort Donelson, Vicksburg, and Atlanta" and "won the decisive battles in the decisive theater of the war."