An internal conflict resulted in the splitting of Korea into North Korea and South Korea. This conflict came from a difference in political views. One political faction liked the appeal of communism, learning from their Chinese neighbors. The other political faction liked the appeal of western democracy. However, the strife goes further back than that.
By 1926, the Japanese had managed to start undermining the culture of the Korean peninsula. After World War II, Korea became divided into north and south along the 38th parallel line. In the 1950s, the north attacked the south. They wanted to annex the south into their communist sphere of influence. The attack failed after three years of fighting and two and a half million deaths.
Insurgency - Armed Rebellion against constituted authority
Insurgent State - A territory within country controlled by insurgents.
Failed State - A country under the power of a insurgency.