The Monroe Doctrine is a policy of the United States introduced on December 2, 1823. It stated that further efforts by European countries to colonize land or interfere with states in the Americas would be viewed as acts of aggression requiring U.S. intervention. The doctrine was introduced by President Monroe when he was enraged at the actions being executed around him. The Monroe Doctrine asserted that the Western Hemisphere was not to be further colonized by European countries but that the United States would neither interfere with existing European colonies nor meddle in the internal concerns of European countries. The Doctrine was issued at a time when many Latin American countries were on the verge of becoming independent from the Spanish Empire. The United States, reflecting concerns raised by Great Britain, ultimately hoped to avoid having any European power take over Spain's colonies.
The US President, James Monroe, first stated the doctrine during his seventh annual State of the Union Address to Congress. It became a defining moment in the foreign policy of the United States and one of its longest-standing tenets, and would be invoked by many U.S. statesmen and several U.S. presidents, including Theodore Roosevelt, Calvin Coolidge, Herbert Hoover, John F. Kennedy, Ronald Reagan and others.
It would have been nearly impossible for Monroe to envision that its intent and impact would persist with only minor variations for almost two centuries. Its primary objective was to free the newly independent colonies of Latin America from European intervention and control (thus ensuring US national security). The doctrine put forward that the New World and the Old World were to remain distinctly separate spheres of influence, for they were composed of entirely separate and independent nations.