The Cold War began in 1946 as tensions grew between capitalist Western nations led by the United States and communist Eastern nations led by the Soviet Union. The Truman Doctrine established U.S. policy of providing economic and military aid to countries resisting Soviet influence. Stalin sought to control Eastern Europe and blockaded West Berlin, but the U.S.-led Berlin Airlift provided food and supplies, preventing West Berlin from falling under Soviet control. By 1947, the world was divided into communist and capitalist spheres as the Cold War escalated.