The Monroe Doctrine is a U.S. doctrine which, on December 2, 1823, stated that European powers were no longer to colonize or interfere with the affairs of the newly independent nations of the Americas. The United States planned to stay neutral in wars between European powers and their colonies. However, if later on these types of wars were to occur in the Americas, the United States would view such action as hostile. President James Monroe first stated the doctrine during his seventh annual State of the Union Address to Congress, a defining moment in the foreign policy of the United States. Most recently, during the Cold War, the Roosevelt Corollary to the Monroe Doctrine (added during the presidency of Theodore Roosevelt) was invoked as a reason to intervene militarily in Latin America to stop the spread of Communism.
The doctrine's authors saw it as a proclamation by the United States of moral opposition to colonialism, but it has subsequently been re-interpreted in a wide variety of ways, including by President Theodore Roosevelt, who asserted the right of the United States to intervene to stabilize the economic affairs of small nations in the Caribbean and Central America if they were unable to pay their international debts. This interpretation, intended to forestall intervention by European powers who had lent money to said countries, has been termed the Roosevelt Corollary to the Monroe Doctrine.
The United Kingdom was torn between monarchical principle and a desire for new markets; South America as a whole constituted, at the time, a much larger market for British goods than the United States. When Russia and France proposed that Britain join in helping Spain regain her New World colonies, Britain vetoed the idea. British naval power, commercial interests, and common cultural, philosophical, and political links to the United States contributed to the strength of the doctrine. Britain was in fact negotiating with the United States before it was announced as to whether the policies in the Monroe Doctrine should be declared jointly (see Lawson below).