The central keynote of the Monroe Doctrine in American foreign policy, articulated in 1823 by President James Monroe, was the principle of opposing European colonialism in the Americas. The doctrine asserted that any European intervention in the political affairs of the Americas would be viewed as a hostile act towards the United States. This policy aimed to safeguard the newly independent nations in Latin America and prevent further European influence in the Western Hemisphere. The Monroe Doctrine marked a significant moment in U.S. foreign policy, asserting American leadership in the region and laying the foundation for future diplomatic stances.