Monroe Doctrine

The Monroe Doctrine is a United States foreign policy position that opposes any foreign interference in the Western Hemisphere. Originally concerned with European colonialism, it holds that any intervention in the political affairs of the Americas by foreign powers is a potentially hostile act against the United States. The doctrine was central to American grand strategy in the 20th century.

President James Monroe first articulated the doctrine on December 2, 1823, during his seventh annual State of the Union Address to Congress (though it was not named after him until 1850). At the time, nearly all Spanish colonies in the Americas either had achieved or were close to independence. Monroe asserted that the New World and the Old World were to remain separate spheres of influence, and that further efforts by European powers to control or influence sovereign states in the region would be viewed as a threat to U.S. security. In turn, the United States would recognize and not interfere with existing European colonies nor meddle in the internal affairs of European countries.

Because the U.S. lacked a credible navy and army at the time of the doctrine's proclamation, it was largely ignored by the colonial powers. While it was successfully enforced in part by the United Kingdom, which used it as an opportunity to enforce its own Pax Britannica policy, the doctrine was ignored several times over the course of the 19th century, notably with the second French intervention in Mexico. By the beginning of the 20th century, in what is regarded as a pivotal moment in the history of its foreign policy, the United States itself was able to successfully enforce the doctrine.