What were Harry S. Truman's most important contributions? Which of his decisions had the greatest effect on history?

it was the "4. potsdam" conference that demanded the unconditional surrender of japan, since it was clear that the japanese would continue to find until the very last man otherwise.

i would say it is the roman empire europe after the norman conquest.

treating native americans justly and giving them equal rights as citizens of the united states" was not a way in which americans sought to solve the indian problem. removal was the most popular idea.

it created the power of judicial review.