History of Cambodia in the context of "Chenla"

The Khmer Empire was an empire in mainland Southeast Asia, centered on hydraulic cities in what is now northern Cambodia. Known as Kambuja (Old Khmer: កម្វុជ; Khmer: កម្ពុជ) by its inhabitants, it grew out of the former civilization of Chenla and lasted from 802 to 1431. Historians call this period of Cambodian history the Angkor period, after the empire's most well-known capital, Angkor. The Khmer Empire ruled or vassalised most of Mainland Southeast Asia and stretched as far north as southern China.

The beginning of the Khmer Empire is conventionally dated to 802, when Khmer prince Jayavarman II declared himself chakravartin (lit. 'universal ruler', a title equivalent to 'emperor') in the Phnom Kulen mountains. Although the end of the Khmer Empire has traditionally been marked with the fall of Angkor to the Siamese Ayutthaya Kingdom in 1431, the reasons for the empire's collapse are still debated amongst scholars. Researchers have determined that a period of strong monsoon rains was followed by a severe drought in the region, which caused damage to the empire's hydraulic infrastructure. Variability between droughts and flooding was also a problem, which may have caused residents to migrate southward and away from the empire's major cities.

The Japanese occupation of Cambodia (Khmer: ការត្រួតត្រារបស់ជប៉ុននៅកម្ពុជា) was the period of Cambodian history during World War II when the Kingdom of Cambodia was occupied by the Japanese. Vichy France, which was a client state of Germany, nominally maintained the French protectorate over Cambodia and other parts of Indochina during most of the Japanese occupation. This territory of Cambodia was reduced, by concessions to Thailand after the Franco-Thai War, so that it did not include Stung Treng Province, Battambang Province, and Siem Reap Province.

The Japanese occupation in Cambodia lasted from 1941 to 1945 and, in general, the Cambodian population escaped the brutalities inflicted on civilians by the Japanese occupiers in other countries of Southeast Asia. After the nominal French Indochina colonial government was overthrown in 1945, Cambodia became a pro-Tokyo puppet state until the surrender of Japan.

Nam tiến (Vietnamese: [nam tǐən]; chữ Hán: 南進; lit. "southward advance" or "march to the south") is a historiographical concept that describes the historic southward expansion of the territory of Vietnamese dynasties' dominions and ethnic Kinh people (Đại Việt) from the 11th to the 19th centuries. The concept of Nam tiến has differing interpretations, with some equating it to Vietnamese colonization of the south and to a series of wars and conflicts between several Vietnamese dynasties and Champa Kingdoms, which resulted in the annexation and Vietnamization of the former Cham states as well as indigenous territories. The nam tiến became one of the dominant themes of the narrative that Vietnamese nationalists created in the 20th century, alongside an emphasis on non-Chinese origin and Vietnamese homogeneity. Within Vietnamese nationalism and Greater Vietnam ideology, it served as a romanticized conceptualization of the Vietnamese identity, especially in South Vietnam and modern Vietnam.

The Vietnamese domain gradually expanded from its original heartland in the Red River Delta into southern territories, which were controlled by the Champa kingdoms. In a span of some 700 years, the Vietnamese domain tripled the area of its territory and more or less acquired the elongated shape of modern-day Vietnam. Beginning in the 20th century, modern Vietnamese historiography, under the auspices of nationalism and racialism, coined the term Nam tiến for what they believed to be a gradual, inevitable southern expansion of Vietnamese domains. According to the 20th-century Vietnamese scholars who constructed the Nam tiến as a continuous historical phenomenon, the 11th to the 14th centuries saw battle gains and losses as frontier territory changed hands between the Viet and the Chams during the early Cham–Viet wars. In the 15th, 16th and 17th centuries, following the Fourth Chinese domination of Vietnam (1407–1427), the Vietnamese defeated the less centralized state of Champa and seized its capital in the 1471 Cham–Vietnamese War. From the 17th to the 19th centuries, Vietnamese settlers penetrated the Mekong Delta. The Nguyễn lords of Huế wrested the southernmost territory from Cambodia by diplomacy and by force, which completed the "March to the South".

Year Zero (Khmer: ឆ្នាំសូន្យ, Chhnăm Sony [cʰnam soːn]) is an idea put into practice by Pol Pot in Democratic Kampuchea that all culture and traditions within a society must be completely destroyed or discarded and that a new "revolutionary" culture must replace it starting from scratch. In this sense, all of the history of a nation or a people before Year Zero would be largely deemed irrelevant, because it would ideally be purged and replaced from the ground up.

The first day of "Year Zero" was declared by Angkar and the Khmer Rouge on 17 April 1975 upon their takeover of Cambodia to signify a rebirth of Cambodian history. Adopting the term as an analogy to the "Year One" of the French Revolutionary Calendar, Year Zero was, in effect, an attempt by the Khmer Rouge to erase history and reset Cambodian society, removing any vestiges of the past.

Nam tiến (Vietnamese: [nam tǐən]; chữ Hán: 南進; lit. "southward advance" or "march to the south") is a historiographical concept that describes the historic southward expansion of the territory of Vietnamese dynasties' dominions and ethnic Kinh people (Đại Việt) from the 11th to the 19th centuries. The concept of Nam tiến has differing interpretations, with some equating it to Vietnamese colonization of the south and to a series of wars and conflicts between several Vietnamese dynasties and Champa Kingdoms, which resulted in the annexation and Vietnamization of the former Cham states, as well as indigenous territories such as those inhabited by the Khmer Krom. The nam tiến became one of the dominant themes of the narrative that Vietnamese nationalists created in the 20th century, alongside an emphasis on non-Chinese origin and Vietnamese homogeneity. Within Vietnamese nationalism and Greater Vietnam ideology, it served as a romanticized conceptualization of the Vietnamese identity, especially in South Vietnam and modern Vietnam.

The Vietnamese domain gradually expanded from its original heartland in the Red River Delta into southern territories, which were controlled by the Champa kingdoms. In a span of some 700 years, the Vietnamese domain tripled the area of its territory and more or less acquired the elongated shape of modern-day Vietnam. Beginning in the 20th century, modern Vietnamese historiography, under the auspices of nationalism and racialism, coined the term Nam tiến for what they believed to be a gradual, inevitable southern expansion of Vietnamese domains. According to the 20th-century Vietnamese scholars who constructed the Nam tiến as a continuous historical phenomenon, the 11th to the 14th centuries saw battle gains and losses as frontier territory changed hands between the Viet and the Chams during the early Cham–Viet wars. In the 15th, 16th and 17th centuries, following the Fourth Chinese domination of Vietnam (1407–1427), the Vietnamese defeated the less centralized state of Champa and seized its capital in the 1471 Cham–Vietnamese War. From the 17th to the 19th centuries, Vietnamese settlers penetrated the Mekong Delta. The Nguyễn lords of Huế wrested the southernmost territory from Cambodia by diplomacy and by force, which completed the "March to the South".