North Korea
Japan tried to suppress Korean traditions and culture and ran the economy primarily for its own benefit. Korean resistance groups known as Dongnipgun (Liberation Army) operated along the Sino-Korean border, fighting guerrilla warfare against Japanese forces. Some of them took part in allied action in China and parts of South East Asia. One of the guerrilla leaders was the communist Kim Il-sung, who later became the first leader of North Korea.
Purge
North Korean leaders Kim Il-sung, Kim Jong-il, and Kim Jong-un have each periodically purged their political rivals or perceived threats, beginning in the 1950s. The most senior Kim purged those who opposed his son's succession to the supreme leadership of North Korea. Kim Il-sung's most prominent purge occurred during the "August Incident" in 1956, when the pro-Soviet and pro-Chinese Yanan factions of the Workers' Party of Korea (WPK) attempted to depose Kim. Most of those involved in the plot were executed while some others fled to the USSR and China. While some purges were carried out under Kim Jong-il, they were not as common as they were under his father/son. Kim Jong-un purged a number of high-ranking officials and generals installed by his father Kim Jong-il in the former's first years in power, including, most prominently, his uncle Jang Sung-taek.