Independence and Vietnam War
The sparse evidence for a Pleistocene human occupation of present day Cambodia are quartz and quartzite pebble tools found in terraces along Mekong River, in Stung Treng and Kratié provinces, and in Kampot Province, but their dating is not reliable. Some slight archaeological evidence shows communities of hunter-gatherers inhabited Cambodia during Holocene: the most ancient Cambodian archeological site is considered to be the cave of Laang Spean, in Battambang Province, which belongs to the so-called Hoabinhian period. Excavations in its lower layers produced a series of radiocarbon dates as of 6000 BC. Upper layers in the same site gave evidence of transition to Neolithic, containing the earliest dated earthenware ceramics in Cambodia Archeological records for the period between Holocene and Iron Age remain equally limited. Other prehistoric sites of somewhat uncertain date are Samrong Sen (not far from ancient capital of Oudong), where first investigations started just in 1877, and Phum Snay, in the northern province of Banteay Meanchey. Prehistoric artifacts are often found during mining activities in Ratanakiri. The most outstanding prehistoric evidence in Cambodia however are probably "circular earthworks", discovered in the red soils near Memot and in adjacent region of Vietnam as of the end of the 1950s. Their function and age are still debated, but some of them possibly date from 2nd millennium BC at least. A pivotal event in Cambodian prehistory was the slow penetration of the first rice farmers from North, which begun in the late 3rd millennium BC. They probably spoke ancestral Mon-Khmer. Iron was worked by about 500 BC. The most part of evidence come from Khorat Plateau, Thai country nowadays. In Cambodia some Iron Age settlement were found beneath Angkorian temples, like Baksei Chamkrong, others were circular earthworks, like Lovea, a few kilometers north-west of Angkor. Burials, much richer, testify improvement of food availability and trade (even on long distances: in the 4th century BC trade relations with India were already opened) and the existence of a social structure and labor organization.
Pre-Angkorian and Angkorian polities
During the 3rd, 4th, and 5th centuries, the Indianised states of Funan and Chenla coalesced in what is now present-day Cambodia and southwestern Vietnam. These states are assumed by most scholars to have been Khmer. For more than 2,000 years, Cambodia absorbed influences from India and China passing them on to other Southeast Asian civilisations that are now Thailand, Vietnam, and Laos. The Khmer Empire flourished in the area from the 9th to the 13th century. Around the 13th century, Theravada Buddhism was introduced to the area through monks from Sri Lanka. From then on Theravada Buddhism grew and eventually became the most popular religion. The Khmer Empire declined yet remained powerful in the region until the 15th century. The empire's centre of power was Angkor, where a series of capitals was constructed during the empire's zenith. Angkor could have supported a population of up to one million people. Angkor, the world's largest pre-industrial settlement complex, and Angkor Wat, the most famous and best-preserved religious temple at the site, are reminders of Cambodia's past as a major regional power.
Dark ages of Cambodia
After a long series of wars with neighbouring kingdoms, Angkor was sacked by the Thai and abandoned in 1432 because of ecological failure and infrastructure breakdown. The court moved the Capital to Lovek where the kingdom sought to regain its glory through maritime trade. The attempt was short-lived, however, as continued wars with the Thai and Vietnamese resulted in the loss of more territory and Lovek was conquered in 1594. During the next three centuries, the Khmer kingdom alternated as a vassal state of the Thai and Vietnamese kings, with short-lived periods of relative independence between.
Modernity and French Indochina
In 1863, King Norodom – who had been installed by Thailand – sought the protection of France from the Thai and Vietnamese, after tensions grew between them. In 1867, the Thai king signed a treaty with France, renouncing suzerainty over Cambodia in exchange for the control of Battambang and Siem Reap provinces which officially became part of Thailand. The provinces were ceded back to Cambodia by a border treaty between France and Thailand in 1906. Cambodia continued as a protectorate of France from 1863 to 1953, administered as part of the colony of French Indochina, though occupied by the Japanese empire from 1941 to 1945. After King Norodom's death in 1904, France manipulated the choice of king and Sisowath, Norodom's brother, was placed on the throne. The throne became vacant in 1941 with the death of Monivong, Sisowath's son, and France passed over Monivong's son, Monireth, feeling he was too independently minded. Instead, Norodom Sihanouk, a maternal grand-son of king Sisowath, who was eighteen years old at the time, was enthroned. The French thought young Sihanouk would be easy to control. They were wrong, however, and under the reign of King Norodom Sihanouk, Cambodia gained independence from France on November 9, 1953.