Monroe Doctrine is the best known U.S. policy toward the Western Hemisphere. Buried in a routine annual message delivered to Congress by President James Monroe in December 1823, the doctrine warns European nations that the United States would not tolerate further colonization or puppet monarchs.
It was the start of the large powerful American military before WW1 the Entirety of the United States Armed Forces could fit in Yankee Stadium now it is over 1 million members strong