Northeast Anti-Japanese United Army
Kim Il-sung, later to become leader of North Korea, was a high-rank officer in this army, and attained a distinction that he invaded China-Korea border and attacked Japanese police station in Bochonbo 1939. It was widely reported by Korean presses such as Donga Ilbo and he became famous in Korea as the most prominent leader of the anti-Japanese movement. After the war, some of the Korean nationals in this army became the first generation of the leaders of North Korea. Besides Kim Il-sung, An Gil, Kim Chaek, Choe Yong-gon and Kang Kon were also Korean high-rank officers of NAJUA, later assumed high positions in North Korea.
Workers' Party of Korea
Kim Il-sung was not the most ardent supporter of a military reunification of Korea; that role was played by the South Korean communists, headed by Pak Hon-yong. After several meetings with Joseph Stalin (the leader of the Soviet Union), the North Koreans invaded South Korea on 25 June 1950—this began the Korean War. With American intervention in the war the DPRK nearly collapsed, but it was saved by Chinese intervention in the conflict. The war had the effect of weakening Soviet influence over Kim Il-sung and the WPK. Around this time, the main fault lines in early WPK politics were created. Four factions formed: domestic (a group of WPK cadres who had remained in Korea during Japanese rule), Soviet Koreans (Koreans sent from the Soviet Union), Yanan (Koreans from China) and guerrillas (Kim Il-sung's personal faction). However, Kim would be unable to further strengthen his position until the end of the war.