The struggle to stay alive dominates the history of Phu Quoc. Compared with the fertile Mekong Delta on the mainland nearby, Phu Quoc has a dry climate and poor soils unsuitable for growing rice. On top of that, it has served as a place of refuge and exile for warlords and rebels and revolutionaries for hundreds of years. Tourists coming from Cambodia for some peace and relaxation may be startled to discover this island has its own "killing fields". Admittedly, they are on a much smaller scale of wickedness than the killing fields of Cambodia.
If this is fate is not unfortunate enough, Phu Quoc also happens to sit on top of one of Asia’s cultural fault lines. This is the border that separates Indian and Chinese influenced Asia. While Vietnam is decidedly Chinese inspired in its culture and religion and cuisine and work ethic, Cambodia belongs to the Indian sphere of influence. When the Chinese and Indian worldviews go to war, Phu Quoc often becomes the battlefield. Despite being closer to mainland Cambodia than mainland Vietnam, Phu Quoc has been inhabited by Vietnamese settlers for hundreds of years. When the French conquered Vietnam in the 19th Century they established rubber and coconut plantations on the island. Pepper (and Chinese pepper farmers) were brought in from China’s Hainan province. When the French departed after the Second World War, South Vietnam’s government took control.
That said, Cambodians have never recognized Vietnam’s claim to Phu Quoc, an island they call Koh Tral. In fact, Cambodians regard all of southern Vietnam including the Mekong Delta and Ho Chi Minh City as part of their ancestral territory, Khmer Krom. When the genocidal Khmer Rouge (Red Cambodians) led by Pol Pot seized power in Cambodia in the 1970s, they embarked on a bid to reclaim Khmer Krom. In 1975 a Khmer Rouge unit raided Phu Quoc and the island of Tho Chu, where they massacred 500 Vietnamese civilians. It was a wake-up call for the newly unified socialist government of Vietnam, and act they did. The Vietnamese army dislodged the Khmer Rouge from Phu Quoc, and within a few years managed to topple Pol Pot’s reign of terror in Cambodia. The Khmer Rouge are gone, but Cambodian aspirations for the return of Phu Quoc live on.