Jeju inhabitants awaiting execution in late 1948. The Jeju uprising, known in South Korea as the Jeju April 3 incident, was an uprising on Jeju Island from April 1948 to May 1949. Residents of Jeju opposed to the division of Korea had protested and had been on a general strike since 1947 against elections scheduled by the United Nations. the First Republic of Korea under President Syngman Rhee escalated the suppression of the uprising from August 1948, declaring martial law. The Jeju uprising was notable for its extreme violence; between 14,000 and 30,000 people (10 percent of Jeju's population) were killed, and 40,000 fled to Japan.