Rosecrans graduated from West Point in 1842, didn't serve in the Mexican War, and left the army in 1854. When the Civil War began, Rosecrans served on George B. McClellan's staff and helped secure West Virginia for the Union. He succeeded John Pope in command of the Army of the Mississippi when Pope was called East. Late in 1862, Rosecrans took command of the newly created Army of the Cumberland and repulsed Braxton Bragg at Murfeesboro. In September 1863, Rosecran's army was badly beaten by the Confederates at Chickamauga. This would be his last major command, as U.S. Grant took over command in Chattanooga. Rosecran retired from the army in 1867, was made minister to Mexico in 1868, and removed from this office by President Grant in 1869. He served as a U.S. congressman from California from 1880 to 1885. Rosecrans died in 1898.