The Kingdom of Cambodia, sometimes referred to by its older name, Kampuchea, is located in South East Asia. Ancient history reveals that it was originally a Hindu-Buddhist empire, the Khmer Empire, which controlled most of Indochina from the 11th through 14th centuries. Its vast territories extended to parts of modern day Thailand, Laos, Myanmar, Malaysia and Vietnam.
Jayavarman II is commonly known as the first king of the Khmer Empire, reigning from 802-834 A.D. The empire continued to gain influence and power under the rule of lesser known kings, whose reigns often ended quickly through violent insurrection.
In the early 12th century, Suryavarman II built the famous Angkor Wat as a Hindu temple dedicated to the god Vishnu. The Khmer Empire reached its summit of greatness, however, under the reign of Jayavarman VII in 1181 A.D. Under his reign,the temple structure around Angkor Wat was enlarged to include Angkor Thom and Bayon. It was also during this time that the religion of the Khmer Empire shifted from Hinduism to Buddhism. After Jayavarman’s death in 1218 A.D. the Khmer Empire began its downfall, never to completely recover.
What occurred in the centuries after Jayavarman VII is largely unknown due to insufficient historical records from this period. The Siamese (Thailand) dominated the Khmer until the 17th century, when Vietnam entered the fight for control over the Khmer. Sometime during this period, Angkor was abandoned for the city of Phnom Penh, probably because of Angkor’s close proximity to their Siamese enemies, making it an easy target for attack. It was also during this time that Vietnam was given the right to settle in the Southern portion of Cambodia by King Chey Chettha II, in exchange for Vietnam’s help against their common enemy, Siam. Cambodia never regained control of this southern portion, including what is now part of modern day Ho Chi Minh City (or Saigon).
While the city of Angkor was never totally abandoned, it was in gross disrepair when “discovered” in 1586 by Antonio da Magdalena, a Capuchin friar. It remained largely hidden to the world, however, until French explorers rediscovered its ancient beauty in the 1850s.
In 1864, France forced King Norodom to sign a treaty making the French protectorate of Cambodia. The continued internal power struggles in the country and hostility from both Thailand and Vietnam, led France to gain further control, establishing Cambodia as a French colony in 1884. To avoid war with France, Thailand also returned much of the land which they had occupied for over a century, including Angkor Wat. After Norodom’s death, France enthroned his eight-year old nephew, Sihanouk, rather than the rightful heir, to maintain power. With the outbreak of World War II, however, Japan won control over Cambodia. Upon Japan’s defeat in 1945, France returned to re-establish its hold over Cambodia. It was not until 1954 that Sihanouk, through skillful diplomacy, achieved Cambodian independence from France.
Internal power struggles characterized Cambodia for the next thirty years. King Sihanouk, desiring a more political than monarchial role, abdicated the throne to his father, choosing instead to run for prime minister. He won 99% of the popular vote in the election, his three opponent parties being the pro-Westerners, the neutralists, and the Communists. Sihanouk called the Communists “Khmer Rouges,” or French for “Red Cambodians”, and the name stuck. When his father died in 1960, Sihanouk named himself Chief of State.
Cambodia was soon taken up in the whirlwind of the Vietnam War. Though the Cambodian government attempted to stay neutral, such a posture was difficult to maintain. During this time Sihanouk began to visibly lose power, and on March 18, 1970, his own government, headed by Lon Nol, deposed him while he was on an extended trip to France. 
On March 23, 1970, Sihanouk met in China with both Vietnamese and Laotian Communist leaders and joined them in their struggle against the American-supported regimes that occupied their countries. He also united with his former enemies, the Khmer Rouge, in order to defeat the Lon Nol government that had deposed him. By October of the same year, the Khmer Rouge, led by Pol Pot (a.k.a. Saloth Sar, a.k.a. “Brother Number One”), occupied half of Cambodia and was rapidly building up their forces.
In the years following, Lon Nol’s government continued to weaken, and when the bombing of Vietnam and Cambodia was halted by the American Congress on Jun 30, 1973, Lon Nol’s forces lost support against the Khmer Rouge.
After several years of civil war, the Khmer Rouge captured the capital, Phnom Penh, on April 17, 1975. While this initially brought celebration and relief to the war-torn country, their joy was quickly turned to horror as the Khmer Rouge began brutally removing city residents from their homes, forcing them into the provinces (countryside) to perform manual labor. Adding to the hardship, a widespread famine affected the entire country. As a U.S. report noted: “…without large scale external food and equipment assistance there will be widespread starvation between now and next February and probably more of the same next year…”
During one of the darkest times in modern history, the Khmer Rouge performed mass annihilation of their own people from 1975 to 1979. Intellectuals, those resembling westerners, former government employees, and those hinting at opposition—all were systematically exposed and executed. Religion was banned, and mass graves were dug and then filled with countless bodies, creating the “killing fields”. Somewhere between one and three million Cambodians died as a result, either by execution, or through the starvation and sickness that resulted from the inhumane conditions imposed upon them by their own people. Devastatingly, son killed father, daughter killed mother, brother killed brother, sister killed sister. In the end, approximately 30% of Cambodia’s population had been exterminated.
Still hungry for power, the Khmer Rouge began entering Vietnamese border villages and butchering the inhabitants, claiming that the land belonged to Cambodia. Vietnam responded in fury to this action by marching into Phnom Penh, taking the capital with little resistance. By this time, the Khmer Rouge were starving and had turned on themselves, with little motivation to fight the invading army.
Vietnam occupied Cambodia for ten years, with some continued resistance from the Khmer Rouge in the northern provinces, where they had retreated. The rebels were eventually subdued and Vietnam installed Hun Sen as foreign minister of the “People’s Republic of Kampuchea”. He served until 1990, with a brief interruption from 1986-87. In 1985 he became Prime Minister, though in 1997 he was forced to share this office with Norodom Ranariddh, the brother of Sihanouk, the king of Cambodia. This forced partnership was soon dissolved by a coup in July of 1997, with Hun Sen overthrowing Ranariddh and becoming the sole prime minister in 1998. Also in 1998, Pol Pot died of natural causes, never being brought to justice.
Today, Cambodia’s government exists as a constitutional monarchy. Sihanouk, who was essentially a prisoner of the Khmer Rouge during their reign, was reinstated in 1993 as king. He reigned until 2004, when he abdicated the throne to his son, Norodom Sihamoni, who is the current monarch of Cambodia. Hun Sen continues to govern as prime minister.
 U.S. Agency for International Development, draft Termination Report for Cambodia, April 1975, Part Six, “Cambodia’s Food and Fibre Needs: The PL 480 Assistance Program to Cambodia for Rise and Other Commodities,” 16-17 as cited in Kiernan, Ben. The Pol Pot Regime: Race, Power, and Genocide in Cambodia Under the Khmer Rouge, 1975-79. New Haven, CT: Yale University Press, 2008, 63.