The primary purpose of the Monroe Doctrine, issued by the United States in the 19th century, was to deter European colonial powers from interfering in the political affairs of Latin America and to assert U.S. influence in the region. President James Monroe declared that any European attempt to colonize further or interfere in the Americas would be viewed as an act of aggression. This doctrine aimed to protect newly independent nations and promote a sense of American hegemony in the hemisphere, thereby shaping foreign policy for decades to come.