Jeju massacre

The Cheju Uprising refers to the rebellion on Jeju island, South Korea, beginning on April 3, 1948. Between 14,000 and 30,000 individuals were killed in fighting between various factions on the island. The suppression of rebellion by the South Korean army has been called “brutal”, resulting in tens of thousands of deaths, the destruction of many villages on the island, and sparking rebellions on the Korean mainland. The rebellion, which included the mutiny of several hundred members of the South Korean 11th Constabulary Regiment, lasted until May of 1949, although small isolated pockets of fighting continued into 1953.
See more at Wikipedia.org...