The Korean War
In June 1950, North Korea invaded South Korea in an attempt to unify the two Koreas as a one unified but communist Korea. This lead to the Korean War with North Korea supported by the Soviet Union and South Korea supported by the United States. China also got involved. It resulted in a stalemate between the two Koreas and the Korean Agreement was signed was signed which set up the Demilitarized Zone (DMZ) to separate the two permanently.