With the Truman Doctrine the US promised what?

The Truman Doctrine was a policy based on a speech given by President Harry F. Truman to a joint session of the US Congress. In his speech, Truman told Congress that "it must be the policy of the United States to support free people who are resisting attempted subjugation by armed minorities or by outside pressures." The focus was on preventing the spread of Communism, especially in the countries of Greece and Turkey, but it effectively changed US Foreign Policy.