Trịnh–Nguyễn War
In the 17th century a weakened Khmer state left the Mekong Delta poorly administered after 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.