A leader of the Democratic Party, he previously served as the 34th vice president from January to April 1945 under Franklin Roosevelt and as a United States senator from Missouri from 1935 to January 1945. Assuming the presidency after Roosevelt's death, Truman implemented the Marshall Plan to rebuild the economy of Western Europe and established both the Truman Doctrine and NATO to contain the expansion of Soviet communism. He proposed numerous liberal domestic reforms, but few were enacted by the conservative coalition that dominated the Congress.
Truman grew up in Independence, Missouri, and during World War I fought in France as a captain in the Field Artillery. Returning home, he opened a haberdashery in Kansas City, Missouri, and was elected as a judge of Jackson County in 1922. Truman was elected to the United States Senate from Missouri in 1934. In 1940–1944 he gained national prominence as chairman of the Truman Committee, which was aimed at reducing waste and inefficiency in wartime contracts. Truman was elected vice president in 1944 and assumed the presidency following the death of Roosevelt. Now acting as president, Truman was informed about the ongoing Manhattan Project and the atomic bomb. 