Truman made a number of critical decisions (correctly, in my view) that set the terms of engagement for the Cold War. He also furthered the cause of African American equality. From Wikipedia:
While
Germany surrendered a few weeks after Truman assumed the Presidency, the war with
Japan was expected to last another year or more. Truman approved the use of
atomic weapons against Japan, intending to force
Japan's surrender and spare American lives in
a planned invasion; the decision remains controversial. His presidency was a turning point in
foreign affairs, as his government supported an
internationalist foreign policy in conjunction with European allies. Working closely with Congress, Truman assisted in the founding of the
United Nations, issued the
Truman Doctrine to contain communism, and passed the $13 billion
Marshall Plan to rebuild Europe, including the
Axis Powers of both
world wars, whereas the
wartime allied Soviet Union became the peacetime enemy, and the Cold War began. He oversaw the
Berlin Airlift of 1948 and the creation of
NATO in 1949. When communist
North Korea invaded
South Korea in 1950, he immediately sent in U.S. troops and gained UN approval for the
Korean War. After initial success, the UN forces were thrown back by Chinese intervention and the conflict was stalemated through the final years of Truman's presidency.
On domestic issues, bills endorsed by Truman often faced opposition from a
conservative Congress dominated by the South, but his administration successfully guided the American economy through post-war economic challenges. He said civil rights was a moral priority and in 1948 submitted the first comprehensive legislation, issuing Executive Orders the same year to start racial integration in the military and federal agencies. Corruption in Truman's administration, which was linked to certain members in the
cabinet and senior White House staff, was a central issue in the
1952 presidential campaign which
Adlai Stevenson, Truman's successor as Democratic nominee, lost to Republican
Dwight D. Eisenhower.
Popular and scholarly assessments of his presidency were initially negative, but eventually became more positive after his retirement from politics. Truman's
1948 election upset to win a full term as president is routinely invoked by underdog candidates.