More History, filling in the gaps with the Lonely Planet guidebook:
Enter the French: From 1600 through 1863, Cambodia was ruled by a number of weak kings, forced to seek protection from either Thailand or Vietnam. Thailand took much of northwest Cambodia. Then, in 1863 French gunboats sailed up the river and intimidated King Norodom I into signing a treaty of protectorate. With the French demanding more internal control of Cambodia, King Norodom had to sign another treaty in 1884, making Cambodia a virtual colony of the French, which sparked a two year rebellion. The French did gain the Cambodian northwest territories back from Thailand, and they maintained the royal court in such splendor that they had not seen since the height of the Angkor period.

Enter King Sihanouk: King Norodom I was succeeded by King Sisowath (1904-1927) and then King Monivong (1927-1941). During World War II, Vichy-France placed nineteen year old Prince Sihanouk on the throne, thinking he would be a pliable ruler. After WW II Cambodia was made an autonomous state within the French union. in 1952 King Sihanouk dissolved parliament, declared martial law, and left the country, in an attempt to drum up international support for independence, and vowed not to return until it was achieved. The French government, wanting to avoid the embarrassment, granted it in on November 9th, 1953. King Sihanouk then abdicated, placed his father on the throne, and created his own political party, which won every seat in parliament in the 1955 elections.

Enter the US and the Khmer Rouge: Sihanouk declared Cambodia neutral in the growing international tensions in Vietnam. More afraid of American allies Thailand and South Vietnam then of the communist North Vietnam, Sihanouk refused military aid from the US. In 1965 he nationalized many industries, including rice trade. Fearful that the US was plotting against him, Sihanouk veered towards North Vietnam and China, allowing the Vietnamese to use Cambodian territory in their conflict with South Vietnam. This alienated many sectors of Cambodian society, including the right wing military and the peasants, who were fed up with government corruption. A rebellion broke out in 1967. Sihanouk succumbed to pressure from the army and enacted harsh measures against the left-wingers. In 1970, while on a trip to France, Silhanouk was deposed by General Lon Nol and Prince Sisowath Sirik Matak, his cousin. Sihanouk took up residence in Beijing and set up his government in exile, in alliance with an indigenous Cambodian revolutionary movement called the Khmer Rouge.

The growth of the Khmer Rouge: General Lon Nol issued an ultimatum to the Vietnamese - leave the country within the week. This no-compromise stance created a civil war in Cambodia. On April 30th, 1975 the US and South Vietnamese armies invaded Cambodia, attempting to flush out the North Vietnamese fighters, but it just drove them and their Khmer Rouge allies deeper into the interior. Within a few months, the pro-Vietnam fighters and their Khmer Rouge allies controlled half of Cambodia. The US continued a policy of carpet bombing east Cambodia for the next 4 years, killing thousands of civilians and driving many more towards the Khmer Rouge.

As the Khmer rouge gained strength and momentum, they turned on their allies, the North Vietnamese. By 1975 most of the North Vietnamese trained Khmer Rouge were executed by the Pol Pot faction. Also executed were the more moderate Khmer Rouge who joined in loyalty to their deposed King.

The US was footing the entire bill for the Lon Nol government, which led to massive corruption and the eventual downfall of his government. Phnom Penh fell to the Khmer Rouge on April 17th, 1975. This date was proclaimed "Year Zero" by the Khmer Rouge.

Reign of the Khmer Rouge: Pol Pot saw the Khmer Rouge as a series of factions that needed cleansing. Vietnamese trained Khmer Rouge fighters were executed, along with anyone loyal to Sihanouk. All senior government and military figures of the Lon Nol government were executed. In their almost four years of rule, between one and two million people perished, either from execution or starvation.

End of the Khmer Rouge government: The Khmer Rouge instigated a number of military incursions into southern Vietnam, claiming the Mekong Delta belonged to Cambodia. On December 25, 1978 the Vietnamese army invaded Cambodia and smashed the Khmer Rouge government within two weeks. They then installed a pro-Vietnam communist government in Phnom Penh, which included the current prime minister, Hun Sen, who had defected to Vietnam in 1977. The Khmer rouge fled westward to the Thai border.

By 1984 the Vietnamese overran all major Khmer Rouge rebel camps within Cambodia, forcing the Khmer Rouge into Thailand. Throughout much of the 1980s the guerrilla war continued. Land mines were laid across Cambodia - by the Khmer Rouge to demoralize their opponents, and by the Vietnamese to seal off the guerrillas. By the end of 1989, all Vietnamese troops were withdrawn from Cambodia.

A UN-sponsored election took place in 1993, with the coalition party led by Sihanouk gaining 58 seats, and the pro-Vietnamese Cambodian People's party gaining 51 seats. This led to a situation of two prime ministers. In the 2003 election, the CPP gained the majority of seats in parliament. The fighting in Cambodia did not end until 1998.