What was the primary assertion of the Monroe Doctrine?

The primary assertion of the Monroe Doctrine, proclaimed by President James Monroe in 1823, was that European nations were prohibited from colonizing or re-establishing control over territories in the Americas. The doctrine emerged in response to the threat of European intervention in the newly independent nations of Latin America. Monroe articulated that the Western Hemisphere was no longer open to European colonial ambitions, which was a significant element in asserting the United States' influence in the region and promoting independence for Latin American countries.

This clear and definitive stance helped establish the United States' role as a protectorate of the Americas, suggesting that any attempts to extend European control would be considered a threat to U.S. security and would provoke a direct response. The Monroe Doctrine thus set the tone for future U.S. foreign policy in the Western Hemisphere and solidified the idea of hemispheric superiority over European interests in the Americas.