Ulysses S. Grant
Before becoming the president, Grant was an officer in the Union Army (North). He fought in the Mexican War and became a general at the start of the American Civil War. He served as head of the Army of Tennessee and won victories at Shiloh, Vicksburg, and Chattanooga. He became the top general in the Union Army from 1864 to 1865, and fought several battles against Robert E. Lee.