Mildly progressive domestically and predominantly isolationist on foreign policy, during the 1930s Vandenberg served on the Nye Committee that investigated the munitions industry's role in precipitating American entry into World War I. He also supported, with reservations, American membership in the World Court. Following the December 1941 Japanese attack on Pearl Harbor, he gradually moved to supporting internationalist policies, publicly renouncing isolationism in 1944. By then a prominent Republican senator, he was crucial in converting his party to internationalism. President Franklin D. Roosevelt made Vandenberg, the ranking Republican on the SFRC, a delegate to the 1945 San Francisco Conference that drew up the final United Nations (UN) Charter. Vandenberg, already suspicious of Soviet motivations, obtained the inclusion of an article permitting the creation of regional security organizations.
Vandenberg represented a large Polish constituency, and he therefore took particular interest in the agreements on Poland and Eastern Europe that Roosevelt, British Prime Minster Winston Churchill, and Soviet leader Josef Stalin concluded at the February 1945 Yalta Conference. President Harry S. Truman deliberately included Vandenberg in the U.S. delegations to postwar meetings of Big Four (U.S., Soviet, British, and Chinese) foreign ministers in New York, Paris, and London intended to resolve remaining questions from World War II, assignments that convinced Vandenberg of the impossibility of dealing with the Soviet Union. He was also a U.S. delegate to the first two sessions of the new UN General Assembly.
The Truman administration's diligent cultivation of Vandenberg proved fruitful. As chairman of the SFRC in 1947 and 1948, he worked assiduously to implement the Truman Doctrine aid program for Greece and Turkey and the Marshall Plan. The Vandenberg Resolution, introduced in 1948, paved the way for Senate approval of the creation of the North Atlantic Treaty Organization (NATO). Although ailing, Vandenberg discouraged the excesses of McCarthyism and accepted, albeit reluctantly, Truman's June 1950 decision to send U.S. troops to war in Korea. Vandenberg died in Grand Rapids on 18 April 1951.
Hill, Thomas Michael. "Senator Arthur H. Vandenberg, the Politics of Bipartisanship, and the Origins of the Anti-Soviet Consensus, 1941–1946." World Affairs 138(3) (Winter 1976): 219–241.; Hudson, Daryl. "Vandenberg Reconsidered: Senate Resolution 239 and American Foreign Policy." Diplomatic History 1(1) (Winter 1977): 46–63.; Tompkins, C. David. Senator Arthur H. Vandenberg: The Evolution of a Modern Republican, 1884–1945. Lansing: Michigan State University Press, 1970.; Vandenberg, Arthur H., Jr., ed. The Private Papers of Senator Vandenberg. Boston: Houghton Mifflin, 1952.