North Korea invaded South Korea and that event signaled the beginning of the Korean War.
The Korean War constituted a war between North Korea receiving the support of China and the Soviet Union; and South Korea, supported by the United Nations, and mainly by the United States (US). The war initiated on 25 June 1950 when North Korea invaded South Korea.
the Korean War kicked off when some 75,000 soldiers from the North Korean People’s Army poured across the 38th parallel.