Ulysses S. Grant was the most acclaimed Union general during the American Civil War and was twice elected President. Grant began his military career as a cadet at the West Point military academy in 1839. After graduation he went on to serve with distinction as a lieutenant in the Mexican–American War. Grant was a keen observer of the war and learned battle strategies serving under Generals Zachary Taylor and Winfield Scott. After the war Grant served at various posts especially in the Pacific Northwest; he retired from the service in 1854. On the onset of the Civil War in 1861, Grant was working as a clerk in his father's leather goods store in Galena, Illinois.
Grant trained Union military recruits and was promoted to Colonel in June 1861. Maj. Gen. John C. Frémont, who viewed in Grant an "iron will" to win, appointed Grant to commander of the District of Cairo. Grant became famous around the nation after capturing Fort Donelson in February 1862 and was promoted to Major General by President Abraham Lincoln. After a series of decisive yet costly battles and victories at Shiloh, Vicksburg, and Chattanooga, Grant was promoted to Lieutenant General by President Lincoln in 1864 and given charge of all the Union Armies. Grant went on to defeat Robert E. Lee after another series of costly battles in the Overland Campaign, Petersburg, and Appomattox. After the Civil War, Grant was given his final promotion of General of the Armed Forces in 1866 and served until 1869. Grant's popularity as a Union war general enabled him to be elected two terms as the 18th President of the United States.