He severed in the Second Seminole War, and he won many promotions for bravery and distingished conduct in the Mexican War. In 1859, he resigned from the military and enter private enterprise until the outbreak of the American Civil War, at which time he joined the Confederate army as a brigadier general. He was soon promoted to full general and replaced Pierre Gustave Toutant Beauregard as commander of the Army of Tennessee in June, 1862. In August, 1862, Bragg invaded Kentucky but was later forced to retreat back to Tennessee. At the Battle of Murfreesboro, he fought Union General William Starke Rosecrans to a draw and withdrew his army from the field. On September, 1863, Bragg once again engaged Rosecrans at the Battle of Chickamauga. Afterward, he was defeated by General Ulysses Simpson Grant at the Battle of Chattanooga. In February, 1864, Bragg was sent to Richmond, Virginia and made military adviser to Jefferson Davis. He was defeated by General William Tecumseh Sherman in Georgia. In February, 1865, he was placed in command of the Army of Tennessee until the end of the war.

After the war he became the chief engineer for Alabama.