What principle was established by the Monroe Doctrine?

The principle established by the Monroe Doctrine was centered on the idea of preventing new European colonies from being established in the Americas. It asserted that the Western Hemisphere was no longer open to colonization by European powers, thereby making it clear that any attempt by Europe to exert influence or establish new colonies in the territory would be viewed as a hostile act against the United States. This doctrine was significant as it marked a shift in U.S. foreign policy, emphasizing the sovereignty of the American continents and promoting a sense of national identity and independence from European intervention.

This foundational principle aimed to protect newly independent countries in Latin America and to prevent the resurgent ambitions of European empires in the region. It underscored U.S. interests in promoting a hemispheric security environment free from European dominance, which would ultimately shape American foreign relations for years to come.