One of the first military leaders to utilize methods that became the tenets of modern warfare, William T. Sherman was an important Union general during the Civil War. The West Point graduate was a staff officer in California during the Mexican War, where he won a brevet for meritorious service. He resigned from the military in 1853 and pursued a career in business. At the beginning of the Civil War, he rejoined the army as a colonel and commanded a brigade at the first Battle of Bull Run. He later suffered setbacks, including a nervous breakdown and some military near-defeats. When Ulysses S. Grant became general in chief, Sherman commanded the large Union army of one hundred thousand men that moved southeast from Dalton, Georgia. Although defeated at Kenesaw Mountain, Sherman captured Atlanta in September 1864. Spreading out his army to span fifty miles, Sherman conducted a scorched-earth campaign against the Confederacy during the famous "March to the Sea."