After seizing power in April 1975, the newly installed Khmer Rouge regime- known locally as the ‘Angkar’ and internationally as Democratic Kampuchea- was quick to live up to its ambitions of reclaiming land lost over the centuries to Vietnam. With the Vietnam war almost over, Southern Vietnam in mid-April was in chaos- a situation which the Cambodian communists seemed eager to exploit.
Just two days after the fall of Phnom Penh the Vietnamese island of Phu Quoc (known as Koh Tral to Cambodians), 15 km off the coast of Kampot, was shelled by forces under the command of Ta Mok’s son-in-law Khe Muth.
Early in May 1975 a Khmer Rouge raiding party briefly held parts of the island, reportedly raising the plain red flag of revolution on the beach. The Provisional Revolutionary Government of South Vietnam (the country would not officially unify for over a year after the fall of Saigon) sent helicopters to strafe the beach. The Cambodians were finally forced off when a contingent of North Vietnamese Army troops arrived to clear them from the island.
On May 10, 1975, Khmer Rouge forces occupied Thổ Chu Island, 120 km south of Phu Quoc and took around five hundred Vietnamese civilians to Cambodia where they were all killed. From May 24 to May 27, 1975, Vietnamese forces attacked and recaptured the island. The Khmer Rouge raided Thổ Chu Island again in 1977, but were repelled.
Cambodian claims to Phu Quoc were dropped in 1976, but border skirmishes continued, culminating in what is remembered in Vietnam as the Ba Chúc massacre.
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