born Jan. 16, 1815, Westernville, N.Y., U.S.
died Jan. 9, 1872, Louisville, Ky.
Union officer during the American Civil War .
A graduate of West Point, he was commissioned in the engineers and sent on a tour of military facilities in Europe (1844), after which he wrote a textbook on war (1846) that became widely used. In 1861 he became supreme commander of Union forces in the western theatre and hurriedly organized large volunteer armies, though the military successes of the following spring were largely due to subordinate generals such as Ulysses S. Grant and John Pope . In 1862 he was appointed general in chief of Union forces, but subsequent reverses in Virginia and conflict with his subordinates and with the secretary of war Edwin M. Stanton resulted in his replacement by Grant in 1864.