The Monroe Doctrine was caused primarily by colonization efforts by European countries and Russia in the Western Hemisphere.
In the Monroe Doctrine, President James Monroe establishes the idea that the Western Hemisphere is no longer open to colonization. In this document, Monrore discusses how the US will not interfer with any colonies already established. However, any attempts by a foreign country to colonize countries (especially in the Latin American countries) would be meet with military confrontation by the United States army.