Sihanouk became king of Cambodia during French colonial rule in 1941 upon the death of his maternal grandfather, King Monivong. After the Japanese occupation of Cambodia during World War II, he secured Cambodian independence from France in 1953. He abdicated in 1955 and was succeeded by his father, Suramarit, so as to directly participate in politics. Sihanouk's political organization Sangkum won the general elections that year and he became prime minister of Cambodia. He governed it under one-party rule, suppressed political dissent, and declared himself Head of State in 1960. Officially neutral in foreign relations, in practice he was closer to the communist bloc. The Cambodian coup of 1970 ousted him and he fled to China and North Korea, there forming a government-in-exile and resistance movement. He encouraged Cambodians to fight the new government and backed the Khmer Rouge during the Cambodian Civil War. He returned as figurehead head of state after the Khmer Rouge's victory in 1975. His relations with the new government declined and in 1976 he resigned. He was placed under house arrest until Vietnamese forces overthrew the Khmer Rouge in 1979.