On 9th September 1948 the People's Republic of North Korea (yeah, right, that's not a republic or run by the people) was established in the divided north of the Korean peninsula. After World War II, Korea had been divided into two occupied zones at the 38th parallel, the north by the Soviet Union and the south by the United States. Korea in the Second World War had been occupied by Japan for many years, and had been forced to support that country.
Less than two years later, after both Soviet and American forces had withdrawn from their respective territories, the North invaded the South, starting the devastation of the Korean War.
Image: By Rishabh Tatiraju (Own work) [CC BY-SA 3.0 (creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons (en.wikipedia.org/wiki/File:Korea_DMZ.svg)