The Monroe DOCTRINE was an American foreign policy statement issued by President James Monroe in 1823. It declared that the United States would not interfere in the affairs of European nations, and that any attempt by a European nation to colonize or interfere with the affairs of any independent state in the Americas would be viewed as an act of aggression against the United States. The DOCTRINE also stated that the United States would not interfere in the internal affairs of any European nation. The DOCTRINE was a major factor in the development of the United States' foreign policy in the 19th century.