In 1823, Great Britain asked the United States to join it in sending a message to

In 1823, Great Britain proposed that the United States join it in issuing a message to European powers concerning their potential interference in the Americas. This led to the creation of the Monroe Doctrine, articulated by President James Monroe in December 1823. The doctrine asserted that the Western Hemisphere was no longer open to European colonization and that any attempts by European nations to extend their influence into the Americas would be viewed as acts of aggression, warranting U.S. intervention.

The Monroe Doctrine was significant because it represented a bold assertion of American influence in the region, aimed at preventing the old colonial powers from reasserting control over newly independent Latin American nations. It established a principle of U.S. foreign policy that would shape relations in the hemisphere for many years to come, signifying an important step in the development of American nationalism and its role as a regional power.