The Monroe Doctrine depended on naval enforcement

How would the Monroe Doctrine be remembered if European powers repeatedly showed that the United States could not enforce it?

Its authority would be limited by American power. Brazil could at times be stronger than the United States, and Theodore Roosevelt used Brazilian naval strength to argue for expanding the U.S. fleet.

The Monroe Doctrine's credibility depended on forces capable of enforcing it. There were periods when Brazil was stronger than the United States. Theodore Roosevelt used Brazilian naval strength as an argument for developing the American fleet. Repeated European challenges would therefore expose the gap between a diplomatic claim and American capacity.