Answer: He wanted to prevent the advance of Communism.
Truman reacted so strongly when North Korea attacked South Korea because he wanted to prevent the advance of Communism.
They believe that governments should meddle into things like economy to improve the lifestyle of others. Socialists usually claim that it is necessary for a government to intervene and deal with businesses and the economy because that ensures that there's equal rights for all people and people are protected from exploitation and monopolies and similar things.
<span>This was the Era of Good Feelings, in which the Federalist party collapsed and the Democratic-Republicans were the dominant force in national politics. There was a desire for unity among the population in the aftermath of the War of 1812, but there were also times in which infighting took place between factions in the Monroe Administration, so not all parts of the political landscape were positive.</span>