On this day in 1948, the Korean Jeju Uprising began when 3,350 communists attacked police stations in Jeju, beginning a war with the US government and Korean collaborators that resulted in approximately 15,000 civilians killed, almost all by state security forces.

The uprising took place following the 1945 surrender of Japan in World War II, ending 35 years of Japanese colonial rule in Korea. In the period following this surrender, "People's Committees" formed throughout Korea, localized autonomous councils tasked with coordinating the transition towards Korean independence.

When the American military government, the United States Army Military Government in Korea (USAMGIK), arrived on Jeju in late 1945, the Jeju People's Council was the only existing government on the island. In 1946, USAMGIK dissolved the provisional People's Republic of Korea and their associated People's Committees on the mainland, escalating tensions on Jeju.

In February 1948, a general strike broke out in opposition to upcoming elections. Participants attacked government installations and fought with police. On March 1st, police fired on a protest, killing six civilians, including a six-year old child.

On April 3rd, 1948, 500 members of the banned communist Workers' Party of South Korea (WPSK), along with 3,000 sympathizers, attacked eleven police stations, targeting police who had previously collaborated with Japanese colonizers. They also attacked positions held by the Northwest Youth League, a far-right paramilitary which had previously committed violence against workers.

This incident is generally regarded as the official beginning of the "Jeju Uprising", fought between the WPSK and the right-wing alliance of the United States, South Korean collaborators, and the Northwest Youth League. The Jeju Uprising lasted until May of 1949, however communist resistance continued into the Korean War (1950 - 1953).

The conflict was characterized by brutal violence and mass deaths, in particular from state repression. 14,373 civilians were killed, 86%-90% of whom victims of soldiers and police. Right-wing death squads committed war crimes with impunity, exterminating entire villages, gangraping women, and executing children.

Lower estimates of the total killed are 30,000 people, about 10% of the island's total population. The governor of Jeju at the time privately reported the death toll to be around 60,000.

Rebels fought back by tactically retreating to bases in mountainous forests and caves. On April 29th, the Korean, non-military, governor of Jeju province defected to the guerrillas, and many police followed. In response, U.S. military provincial governor William F. Dean ordered a purge of WPSK sympathizers from the ranks of the Korean police, and three sergeants were summarily executed.

In March 1949, Republic of Korea (ROK) forces launched a final eradication campaign, killing 2,345 guerrillas and 1,668 civilians, marking an end to the rebellion. After the Korean War between North and South broke out the following year, the South Korean government rounded up and summarily executed suspected leftists on the island.