repeated warfare with Siam. Concurrently Vietnamese refugees fleeing the Trịnh–Nguyễn War in Vietnam migrated into the area. In 1623 Cambodian king Chey Chettha II (1618–1628) officially sanctioned the Vietnamese immigrants to operate a custom house at Prey Nokor, then a small fishing village. The settlement steadily grew soon becoming a major regional port, attracting even more settlers. In 1698 the Nguyễn Lords of Huế commissioned Nguyễn Hữu Cảnh, a Vietnamese noble to organize the territory along Vietnamese administrative lines, thus by de facto detaching it from the Kingdom of Cambodia and incorporating it into Vietnam. With the loss of the port of Prey Nokor, then renamed Sài Gòn, Cambodia's control of the area grew increasingly tenuous while increasing waves of Vietnamese settlers to the Delta isolated the Khmer of the Mekong Delta from the Cambodian kingdom. By 1757 the Vietnamese had absorbed the provinces of Psar Dèk (renamed Sa Đéc in Vietnamese) on the Mekong itself, and Moat Chrouk (Vietnamized to Châu Đốc) on the Bassac River. Minh Mạng enacted assimilation policies upon the Khmer such as forcing them to adopt Sino-Vietnamese surnames, culture, and clothing. Minh Mang sinicized ethnic minorities including the Cambodians, in line with Confucianism as he diffused Vietnamese culture with China's Han civilization using the term Han people 漢人 for the Vietnamese. Minh Mang declared that "We must hope that their barbarian habits will be subconsciously dissipated, and that they will daily become more infected by Han [Sino-Vietnamese] customs." These policies were directed at the Khmer and hill tribes. Separatist movements Khmer nationalist Son Ngoc Thanh (1908–77) was a Khmer krom, born in Trà Vinh, Vietnam. Thanh was active in the independence movement for Cambodia. With Japanese support he became the prime minister of Cambodia in March 1945 but was then quickly ousted with the return of the French later that year. Widely supported by the Khmer Krom during the First Indochina War, Thanh's role faded in Vietnam after 1954 as he became more embroiled with politics in Cambodia proper, forming an opposition movement against Prince Sihanouk. During the Vietnam War and direct American involvement between 1964 and 1974, the Khmer Krom were recruited by the United States Armed Forces to serve in MIKE Force. The force fought on the side of South Vietnam against the Viet Cong but in time the militia regrouped as the "Front for the Struggle of Kampuchea Krom" (). Headed by