Harry S. Truman was the 33rd President of the United States, serving from April 12, 1945, to January 20, 1953. A member of the Democratic Party, he assumed the presidency after the death of Franklin D. Roosevelt. Truman is known for his decisive leadership during the final months of World War II, including the controversial decision to use atomic bombs on Hiroshima and Nagasaki, which contributed to Japan's surrender. He also played a significant role in the early stages of the Cold War, implementing the Truman Doctrine to contain communism and establishing NATO.