John Quincy Adams's greatest diplomatic service was his role as secretary of state during James Monroe's two terms as president. As secretary of state, Adams suggested and outlined the Monroe Doctrine, establishing one of the major foundations for all future American foreign policy (see James Monroe in the "Presidents" section to read about the Monroe Doctrine.)

John Quincy Adams has been called "one of the greatest secretaries of state" in the history of the United States and is often credited with "the greatest diplomatic victory ever won by a single individual in the history of the U.S." Do you know what that victory was? (Hint: It's not the Monroe Doctrine!)