The Korean War was fought between the Republic of Korea (which had American support) and the Democratic People’s Republic of Korea (which was supported by China and the Soviet Union.) This was but the start of the Cold War between the Soviet Union and the U.S., the two countries never actually fighting each other, but none the less on opposite ends of the political spectrum.
On this day June 28th, in 1950, the Democratic People’s Republic of Korea (now called North Korea) captures the Capital of South Korea, Seoul. Kim Ill Sung, the founder of North Korea, was responsible for the invasion. He also created the North Korean concept of Juche, which was his political thesis. It upheld guidelines for what the government must do, grounding everything on the notion of self-reliance. It is for this reason that North Korea did not accept any aid for many decades for its malnourished citizens.
South Korea would eventually win Seoul back with the help of American troops. Seoul now has a population over 10 million, and it has a metropolitan area topping 25 million. Like many mega cities, Seoul was built next to a river, the Han River. South Korea has remained a Republic, unlike China and North Korea which are both Communist countries, although China is far more liberal than North Korea. South Korea also has a population almost twice the size of North Korea, at nearly 50 million.