He joined the Union Army shortly after the American Civil War broke out in 1861 and rose to prominence after winning early Union victories in the western theater. In 1863, he led the Vicksburg campaign, which gained control of the Mississippi River, dealing a serious strategic blow to the Confederacy, splitting it in two. President Abraham Lincoln promoted him to lieutenant general after his victory at Chattanooga. For thirteen months, Grant fought Robert E. Lee during the high-casualty Overland Campaign and at Petersburg. After Lee fled Petersburg, Grant surrounded and captured his army at Appomattox. On April 9, 1865, Lee formally surrendered to Grant. A week later, Lincoln was assassinated and was succeeded by Andrew Johnson, who promoted Grant to General of the Army in 1866. Later, Grant openly broke with Johnson over Reconstruction policies; Grant used the Reconstruction Acts, which had been passed over Johnson's veto, to enforce civil rights for recently freed African Americans.
A war hero, drawn in by his sense of duty, Grant was unanimously nominated by the Republican Party and was elected president in 1868. 