Which doctrine was established to justify American intervention in the Western Hemisphere?

The Monroe Doctrine was established in 1823 primarily as a response to European colonial expansion and intervention in the Americas. Its core principle was that any attempt by European powers to interfere in the affairs of states in the Western Hemisphere would be seen as acts of aggression towards the United States. This doctrine aimed to protect newly independent nations in Latin America from European colonization and intervention.

In addition to asserting the sovereignty of these nations, the Monroe Doctrine implied that the United States would take an active role in preventing European encroachments. Thus, it established a key foundation for American foreign policy in the Western Hemisphere, asserting the United States' position as the dominant power in the region and justifying intervention in the affairs of its neighbors when deemed necessary.

The other choices refer to different contexts and time periods. The Truman Doctrine focused on containing communism during the Cold War, the New Deal addressed economic recovery during the Great Depression, and the Roosevelt Corollary expanded on the Monroe Doctrine by explicitly stating that the U.S. would intervene in Latin America to maintain stability and prevent European powers from taking control. However, the original doctrine that specifically addresses American intervention in the Western Hemisphere is the Monroe Doctrine.