Kim Il-sung was the leader of North Korea from its founding in early 1948 until his death, when he was succeeded by his son Kim Jong-il. He held the posts of Prime Minister from 1948 to 1972 and President from 1972 to his death. He was also the General Secretary of the Workers Party of Korea where he exercised autocratic power. As leader of North Korea, he ended up switching from a Marxist-Leninist ideology to his self-developed Juche idea and established a personality cult. North Korea officially refers to him as the "Great Leader" and he is designated in the constitution as the country's "Eternal President". His birthday and the day of his death are public holidays in North Korea.