Why did the United States get involved in the Korean War?

Question

The United States wanted to help Great Britain since it was its ally.
The North Korean army had directly threatened the United States.
Communist North Korea had shown aggressive actions toward Japan and China.

Answer 1

The United States got involved in the Korean War primarily because the North Korean army invaded South Korea in June 1950. The United States saw this as a direct threat to its interests in the region and to the spread of communism. Additionally, as part of its containment policy towards communism, the United States felt it was necessary to intervene to prevent the further spread of communism in Asia. The US also had strategic interests in protecting Japan and preventing the domino effect of one country falling to communism leading to others following suit.