James K. Polk
James Knox Polk, considered by many to be one of the greatest American Presidents, was the 11th president of the United States. He was elected in 1844 as a Democrat and served as president from 1845-1849.
Polk was an early pioneer of the Bush Doctrine of preventive war, launching an invasion of Mexico to prevent an imminent Mexican attack on Texas. Unfortunately, Polk was unable to prevent several thousand Mexicans from entering the country and gaining citizenship when the United States annexed California and New Mexico. Polk has also been criticized for accepting a compromise settlement with England over the Oregon Country instead of pursuing a preventive war with Canada in order to gain all of it.
Polk declined to run for a second term.