America was nearing complete recovery from the great depression under the longest sitting president in American history, Franklin D. Roosevelt. The FBI was engaged in bloody confrontations with organized crime. The nation was divided between making deals with Germany under its new leader, Adolph Hitler, and confronting Germany's expansionist goals, but began to be involved in the war already in progress in 1941, after Pearl Harbor was bombed by the Japanese. The rest of the decade was dominated by the war. Harry Truman succeeded Roosevelt as president when FDR died in 1945, continuing the 16-year rule of the Democratic party. In March of 1945, the president authored the Truman Doctrine that resolved to fight the spread of communism. Many technical advances were made during the war. One of these was the atomic bomb. Two such bombs were dropped on Japan to end the final chapter of World War II.