Before World War II, Michigan senator Arthur Vandenberg argues that the United States should avoid all foreign entanglements. The Japanese attack on Pearl Harbor converts him from isolationism to internationalism. The Republican Vandenberg then works closely with Democratic President Harry Truman to forge a bipartisan foreign policy. In 1948, he writes the Vandenberg Resolution, which endorses regional defense alliances. This leads to the Senate’s approval in 1949 of the North Atlantic Treaty, which founds NATO, a defensive alliance between the United States and Western European nations against the Soviet Union and its Eastern European satellites.