Dean Acheson was U.S. secretary of state under President Harry Truman and a major architect of U.S. foreign policy after World War II. He helped formulate an active role for the United States in the postwar world, reversing early isolationist policies. During a period as undersecretary of state to George C. Marshall, Acheson helped develop a policy of containment toward communism and to secure aid for Turkey and Greece against Communist-back insurgents in 1947. Acheson also helped to draft the Marshall Plan to rebuild Western Europe. As secretary of state, he supported the formation of the North Atlantic Treaty Organization. Relative to Asia, he helped distance the United States from the Chinese Nationalist regime on Taiwan, while rejecting recognition of the Communists regime on the mainland.