The Korean War began after North Korean forces crossed the 38th parralel and steamrolled through South Korea, which led to the quick assembly of a UN force comprising of mainly US troops who secured a area around the port city of Busan.
the Korean War began in 1950 when North Korean communist Army came into the 38th parallel and invaded non-communist South Korea.
Explanation:
so the main reason that this war happened was because of the spread of Communism during the Cold War and Japanese Occupation of Korea during World War II
