Which policy statement warned European powers against further colonization in the Western Hemisphere?

• A. Monroe Doctrine
• B. Open Door Policy
• C. Truman Doctrine
• D. Marshall Plan

Answer: (A)

The main idea here is how the United States framed its relationship with Europe in the Western Hemisphere and asserted its influence over regional affairs. The Monroe Doctrine, issued in 1823, states that the Western Hemisphere was off-limits to new European colonization and that any attempt by European powers to control or interfere with independent nations in the Americas would be viewed as a threat to U.S. peace and security. It also established a move toward U.S. leadership in the region, signaling that the Americas should be free from European intervention. While it didn’t immediately deploy force, it laid the groundwork for future American policy and justified later actions when U.S. interests were involved, such as the Roosevelt Corollary expanding into the Caribbean.

In contrast, the Open Door Policy dealt with equal trading rights in China, the Truman Doctrine focused on containing communism after World War II, and the Marshall Plan aimed to rebuild Europe economically after the war. None of those address warning European powers about colonization in the Western Hemisphere, so the Monroe Doctrine is the best fit.