On the night of April 12, 1945, Truman was urgently summoned to the White House, where he was met by Eleanor Roosevelt, who informed him that President Roosevelt was dead. Shocked, Truman asked Mrs. Roosevelt, 'Is there anything I can do for you? Relations with the Soviet Union declined after 1945, and by 1947 the two countries had entered a period of geopolitical tension known as the Cold War. In 1947, Truman promulgated the Truman Doctrine, which called for the United States to prevent the spread of Communism through foreign aid and other means. The following year, he convinced Congress to approve the Marshall Plan, a massive aid package designed to rebuild Western Europe. In 1949, Truman presided over the creation of NATO, an alliance of Western countries opposed to the Soviet Union.