When the South seceded, Breckinridge was briefly a U.S. Senator from Kentucky, but was kicked out of the Senate. After that, he became active in the Confederacy. During the American Civil War, he was a general in the Confederate States Army. He fought in Tennessee and the Shenandoah Valley. He was the Confederate commander at the Battle of New Market. Breckinridge was the last Confederate Secretary of War. After the war, Breckinridge left the country for four years. He returned to Kentucky in 1869 and died in 1875.