-Time period: 1950-1953
The seed for the Korean War was planted in 1905, at the end of the Russo-Japanese War. After this war, Japan annexed the Korean Peninsula. During World War Two, the Allied powers promised freedom to Korea once Japan was defeated. So, when World War Two ended, the Allies split the Korean Peninsula at the 38th Parallel of latitude. The Russian government controlled and established North Korea above the Parallel, while the United States established South Korea below it. Both Russia and the U.S. then left the Korean Peninsula.
After the Allied powers left, North Korea attacked the peaceful South Korea. Seeing little chance of both Koreas reuniting peacefully, Russia aided North Korea by providing them with military equipment and troops. That way, North Korea would be able to win and end the conflict quickly, establishing a communist government. Because of this, the U.S., playing global police, sent in their army to fight alongside South Korea and protect them.
After 3 years of fighting without either side gaining much ground against the other, Russia and the U.S. made peace by withdrawing their armies and letting North and South Korea remain independent countries. North and South Korea remain independent countries to this date.