The Monroe Doctrine established the principle that any intervention in the politics of the Americas by external powers would be viewed as a hostile act against the United States. Introduced by President James Monroe in 1823, the doctrine aimed to show that the US was the sole influence over political matters in the hemisphere and declared that there would be no further colonization of the Americas by European nations. The importance of the doctrine was that it helped the Americas establish independence and become their own nations free from European influence.