Rosecrans graduated in 1842 from the United States Military Academy where he served in engineering assignments as well as a professor before leaving the Army to pursue a career in civil engineering. At the start of the Civil War, leading troops from Ohio, he achieved early combat success in western Virginia. In 1862 in the Western Theater, he won the battles of Iuka and Corinth while under the command of Maj. Gen. Ulysses S. Grant. His brusque, outspoken manner and willingness to quarrel openly with superiors caused a professional rivalry with Grant (as well as with Secretary of War Edwin M. Stanton) that would adversely affect Rosecrans' career.