President Theodore Roosevelt's assertive approach to Latin America and the Caribbean has often been characterized as the "Big Stick," and his policy came to be know as the Roosevelt Corollary to the Monroe Doctrine. Although the Monroe Doctrine of 1823 was essentially passive (it asked that Europeans not increase their influence or recolonize any part of the Western Hemisphere), by the 20th century a more confident United States was willing to take on the role of regional policeman. In the early 1900s Roosevelt grew concerned that a crisis between the Dominican Republic and its creditors could spark an invasion of that nation by European powers. The Roosevelt Corollary of December 1904 stated that the United States would intervene as a last resort to ensure that other nations in the Western Hemisphere fulfilled their obligations to international creditors and did not violate the rights of the United States or invite "foreign aggression to the detriment of the entire body of American nations." As the corollary worked out in practice, the United States increasingly used military force to restore internal stability to nations in the region. Roosevelt declared that the United States might "exercise international police power in 'flagrant cases of such wrongdoing or impotence.'" Over the long term the corollary had little to do with relations between the Western Hemisphere and Europe, but it did serve as justification for U.S. intervention in Cuba, Nicaragua, Haiti, and the Dominican Republic.
Richard H. Collin. Theodore Roosevelt's Caribbean: The Panama Canal, The Monroe Doctrine, and the Latin American Context (Baton Rouge, Louisiana, 1990).
Edmund Morris. Theodore Rex (New York: Random House, 2001).