Cambodian irredentism is a nationalist movement in Cambodia that refer to the land that used to be part of the Khmer Empire. The irredentist movement in Cambodia is aimed against the control by Thailand, Vietnam and Laos. Irredentist, official and unofficial Cambodian claims on territories viewed by Cambodians as having been under some form of Cambodian sovereignty, are rhetorically tied back to an accused expansionism. History Up until the establishment of the Thai and Laotian states, the Khmer Empire was the major land power and a dominant force in mainland Southeast Asia. The territory of Cambodia encompassed most of what would be now Thailand, Laos, part of Myanmar and Southern Vietnam; in an extent, it encroached to even mainland Malaysia. However, subsequent problems and turmoils, as well as the rapid advance by the Vietnamese, Laotians and Thais brought Cambodia's empire into a declining state. Among all, the Thais and the Vietnamese were seen to have done the most harm to Cambodia, causing significant physical traumas for the people of the nation. In order to survive, Cambodia came under a French protectorate, only to find itself being grouped within Vietnamese-dominated French Indochina, and with the French favoring Vietnamese instead of Cambodians. At the outbreak of the First Indochina War Khmer irredentism began to rise. Nonetheless, it was not officially espoused until 1970 when Lon Nol overthrew the monarchy and replaced it with a Republic, where it became increasingly nationalistic and chauvinist, leading to the persecution and massacres of ethnic Vietnamese and Chams. The Khmer Rouge later inherited these nationalistic sentiments which were part of the driving force for the persecution and massacres of Vietnamese in Cambodia as a part of the Cambodian Genocide, and which also was one the motivations for Khmer Rouge incursions in Vietnam and occupations of Vietnamese territories which resulted in several massacres of Vietnamese civilians, the most notorious of which was the Ba Chúc massacre. Modern irredentism Mekong Delta The Cambodians hold a significant amount of hostility to Vietnam with regard to their loss of the Mekong Delta to the Vietnamese in history, and the subsequent enforced Vietnamization and conflicts which Vietnam repeatedly occupied the country, French favoritism to the Vietnamese, and the lack of cultural commonalities with Vietnam being part of the Sinosphere while Cambodia belongs to the Indosphere; this often drew Cambodian nationalist sentiment with the desire to reclaim territory from Vietnam. Both Lon Nol