America’s “Backyard” Rule: The Monroe Doctrine
It’s not law—but it still shapes how the U.S. reacts to power plays in the Americas.
The Monroe Doctrine is a U.S. foreign policy warning from 1823 that never retired.
It treats the Americas as a special U.S. security zone.
It’s not law—but invoking it changes what actions seem justified.
The Monroe Doctrine started in 1823 as part of President James Monroe’s annual message to Congress. At the time, European empires were still expanding, and the United States drew a line: new efforts by Europe to control territory or politics in the Americas would be viewed as a threat to U.S. security.
The doctrine didn’t create a law. It didn’t establish an alliance. It didn’t include enforcement rules. It was a warning—and warnings only work if people keep repeating them.
That’s what happened. Over time, U.S. leaders treated the Monroe Doctrine like a standing assumption: the Western Hemisphere is different. When non-hemispheric powers increase military presence, political influence, or strategic control in the region, the U.S. claims a special interest.
The meaning of the doctrine has shifted with each era. It’s been used to justify restraint, intervention, sanctions, and security partnerships. The original words stayed the same, but what leaders thought they authorized changed with global power dynamics.
Today, when the Monroe Doctrine is referenced, it usually signals one thing: outside influence in Latin America or the Caribbean isn’t being treated as normal diplomacy. It’s being framed as a security issue—and that framing expands the range of U.S. responses.
Go deeper: How the Monroe Doctrine Works
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These sources explain the origin, content, and modern interpretation of the Monroe Doctrine.
U.S. Department of State, Office of the Historian — The Monroe Doctrine, 1823 (n.d.)
https://history.state.gov/milestones/1801-1829/monroeU.S. National Archives — Monroe Doctrine (1823) (2022)
https://www.archives.gov/milestone-documents/monroe-doctrineLibrary of Congress — Monroe Doctrine: Primary Documents in American History (updated guide)
https://guides.loc.gov/monroe-doctrineU.S. Senate Historical Office — President James Monroe’s Annual Message to Congress, December 2, 1823 (primary source)
https://www.senate.gov/about/images/documents/annual-message-monroe-doctrine-1823-nara.htmMiller Center, University of Virginia — Seventh Annual Message (Monroe Doctrine) (annotated presidential speech)
https://millercenter.org/the-presidency/presidential-speeches/december-2-1823-seventh-annual-message-monroe-doctrine