In his annual messages to Congress in 1904 and 1905, President Theodore Roosevelt expanded the Monroe Doctrine. The corollary stated that not only were the nations of the Western Hemisphere not open to colonization by European powers, but that the United States had the responsibility to preserve order and protect life and property in those countries.
European intervention in Latin America (see the Platt Amendment) resurfaced as an issue in U.S. foreign policy when European governments began to use force to pressure several Latin American countries to repay their debts. For example, British, German, and Italian gunboats blockaded Venezuela’s ports in 1902 when the Venezuelan government defaulted on its debts to foreign bondholders. Many Americans worried that European intervention in Latin America would undermine their country’s traditional dominance in the region.
To keep other powers out and ensure financial solvency, President Theodore Roosevelt issued his corollary. "Chronic wrongdoing...may in America, as elsewhere, ultimately require intervention by some civilized nation," he announced in his annual message to Congress in December 1904, "and in the Western Hemisphere the adherence of the United States to the Monroe Doctrine may force the United States, however reluctantly, in flagrant cases of such wrongdoing or impotence, to the exercise of an international police power."
Roosevelt tied his policy to the Monroe Doctrine, and it was also consistent with his foreign policy of "walk softly, but carry a big stick." Roosevelt stated that in keeping with the Monroe Doctrine, the United States was justified in exercising "international police power" to put an end to chronic unrest or wrongdoing in the Western Hemisphere.
This so-called Roosevelt Corollary—a corollary is an extension of a previous idea—to the Monroe Doctrine contained a great irony. The Monroe Doctrine had been sought to prevent European intervention in the Western Hemisphere, but now the Roosevelt Corollary justified American intervention throughout the Western Hemisphere. In 1934, Franklin D. Roosevelt renounced interventionism and established his Good Neighbor policy within the Western Hemisphere.