Nam tiến refers to the southward expansion of the territory of Vietnam from the 11th century to the mid-18th century. The territory of Vietnam was gradually expanded to the south from its original heartland in the Red River Delta. In a span of some 700 years, Vietnam tripled its territory in size and more-or-less acquired its elongated shape of today. The direction of expansion to the south could be explained by geographic and demographic factors. With the South China Sea to the east, the Truong Son Mountains to the west, and China to the north, the Vietnamese polity pushed south, following the coastal plains. The 11–14th centuries saw battle gains and losses as the frontier territory changed hands between the Vietnamese and Chams. In the 15–17th centuries following the failed Ming conquest, the resurgent Vietnamese took the upper hand, defeating the less-centralized state of Champa, forcing the cession of more land. By the 17–19th centuries, Vietnamese settlers had penetrated the Mekong Delta. The Nguyen Lords of Hue by diplomacy and force wrested the southernmost territory from Cambodia, completing the "March to the South".
History
The native inhabitants of the Central Highlands are the Degar peoples. Vietnam conquered and annexed the area during its "march to the south". Cham provinces were seized by the Nguyen Lords. Provinces and districts originally controlled by Cambodia were taken by Vo Vuong. Cambodia was constantly invaded by the Vietnamese Nguyen Lords. Around a thousand Vietnamese settlers were slaughtered in 1667 in Cambodia by a combined force of Chinese and Cambodians. Vietnamese settlers started to inhabit the Mekong Delta that was previously inhabited by the Khmer and in response the Vietnamese were subjected to Cambodian retaliation. The Cambodians told Catholic European envoys that the Vietnamese persecution against Catholics justified retaliatory attacks launched against the Vietnamese colonists. Vietnamese Emperor Minh Mang enacted the final conquest of the Champa Kingdom after the centuries long Cham–Vietnamese wars. The Cham Muslim leader Katip Suma was educated in Kelantan and came back to Champa to declare a Jihad against the Vietnamese after Emperor Minh Mang's annexation of Champa. The Vietnamese coercively fed lizard and pig meat to Cham Muslims and cow meat to Cham Hindus against their will to punish them and assimilate them to Vietnamese culture. Minh Mang sinicized ethnic minorities such as Cambodians, claimed the legacy of Confucianism and China's Han dynasty for Vietnam, and used the term Han people 漢人 to refer to 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 customs." These policies were directed at the Khmer and hill tribes. The Nguyen lordNguyen Phuc Chu had referred to Vietnamese as "Han people" in 1712 when differentiating between Vietnamese and Chams. The Nguyen Lords established đồn điền after 1790. It was said "label=none" by the Gia Long Emperor when differentiating between Khmer and Vietnamese. Minh Mang implemented an acculturation integration policy directed at minority non-Vietnamese peoples. Thanh nhân 清人 or Đường nhân 唐人 were used to refer to ethnic Chinese by the Vietnamese while Vietnamese called themselves as Hán dân and Hán nhân in Vietnam during the 1800s under Nguyễn rule. Extreme anti-Vietnamese sentiment due to Vietnam's conquest of previously Cambodian lands which are now the Mekong delta part of modern-day Vietnam and hundreds of years of Vietnamese invasions, Vietnamese settlers in Cambodia and Vietnam's military subjugation of Cambodia, has led to extreme anti-Vietnamese feelings against ethnic Vietnamese in Cambodia and against Vietnam, and in turn has led to pro-China sentiment among the Cambodian government and the Cambodian opposition, including in the SouthChina Sea, leaving Americans unaware of this to be puzzled by pro-China leanings in Cambodia.
