Conversation so far:
when did the korean war start and when did it end
The Korean War began on 25 June 1950. The fighting ended on 27 July 1953. However, no peace treaty was signed, and the two Koreas are technically still at war.
why did the Korean War start
The war began when North Korea invaded South Korea.
who else was involved in the Korean War, besides North and South Korea
The Korean War was between North Korea (with the support of China and the Soviet Union) and South Korea (with the support of the United Nations, principally the United States).

Question: why did the US get involved
Self-contained rewrite: why did the United States get involved in the Korean War