Shortly after he served as President, Truman was generally seen as a fair President, but historians have boosted his ratings with the hindsight of many decades. It is clear that Truman's reputation suffered from following the effervescent and extremely popular Franklin D. Roosevelt, but Truman was in many ways also a very good President. 

For example, though he was not even briefed by Roosevelt on the development of the atomic bomb when he was Vice President, Truman was quickly able to come up to speed after assuming the presidency in April of 1945, in the waning days of World War II. He made the decision to detonate atomic bombs over the Japanese cities of Hiroshima and Nagasaki, a decision that has since that time been debated but that he felt was necessary at the time to spare countless American and allies's lives in an amphibious attack on Japan. Shortly after the bombs were dropped, Japan surrendered and World War II was over. He went on to fight Communism through the Truman Doctrine and the Marshall Plan, which provided aid to Greece, Turkey, and other European countries that seemed to be teetering toward Communism in the aftermath of the devastation of World War II. He also helped found the United Nations and spearheaded the fighting of the Korean War (under the aegis of the United Nations), which wound up in a stalemate and is considered by many experts to have been a failure.

Domestically, Truman was very liberal and attempted to pass a series of progressive programs known collectively as the Fair Deal. However, he faced opposition from Congress, including from southerners in his own party (the Democrats) who did not want to pass the civil rights legislation he proposed. He also wanted to repeal the Taft-Hartley Act, which limited the rights of labor unions, but was unable to do so. As he faced a conservative Congress, the only major element of his Fair Deal that became law was the Housing Act of 1949, which helped construct public housing. Interestingly, he also proposed national health insurance, which finally became law under President Obama. His agenda was largely checked by a conservative Congress and a conservative and wary mood in the nation after the war and during the beginning of the Cold War. However, he should be appreciated for having a sweeping and progressive agenda for the nation that was in many ways ahead of its time.