Cambodia is struggling to recover from the legacy of the Khmer Rouge's murderous rule in the 1970s, a holocaust that killed almost a quarter of the country's population.

Disagreement persists over the number who died between 1975 and 1979. The Cambodian Genocide Program at Yale University puts the death toll at approximately 1.7 million.

But researchers from the associated Documentation Center of Cambodia (DC-Cam), a non-governmental organisation recording Khmer Rouge atrocities, have not ruled out a figure as high as 3.3 million.

Whatever the statistics, the collective trauma inflicted by the Khmer Rouge and its fanatical leader, Pol Pot, will take generations to heal.

Signs of economic recovery are emerging, but the country still struggles with corruption, poverty and political instability.

The Khmer Rouge started in the 1960s as the opposition Communist Party of Kampuchea. The movement was led by a failed electronics student called Saloth Sar, who had become a communist while studying in Paris.

The Khmer Rouge turned from political to armed struggle in 1969 and Saloth Sar adopted his now infamous nom-de-guerre, Pol Pot. The U.S. military, meanwhile, launched a campaign of secret bombing missions over Cambodia aimed at flushing out Viet Cong forces from neighbouring North Vietnam. And in 1970, Prince Norodom Sihanouk was deposed in a coup led by a pro-American general in his government, Lon Nol.

Popular outrage at the U.S. bombings strengthened support for the Khmer Rouge. When the Vietnam War finally ended, an emboldened Khmer Rouge - backed by China - turned its full attention to securing domestic supremacy. At the same time, Lon Nol's regime began to collapse under its own corruption and incompetence, and the Khmer Rouge finally seized power in Phnom Penh on April 17, 1975.

Initially hailed by the population as revolutionary liberators, Pol Pot and his ultra-Maoist cadres - describing themselves as 'Angkar' or the Organisation - quickly set about fulfilling their vision of a communist agrarian utopia.

In a radical experiment in social engineering, Pol Pot declared 'Year Zero', abolishing money and private property and evacuating hundreds of thousands of urban residents to a nationwide network of rural work camps and security centres. Anyone suspected of any kind of intellectual, religious or government background was singled out as a "class enemy" and murdered.

When the Khmer Rouge regime - which named the country Democratic Kampuchea (DK) - began to fail disastrously in its attempt to create national self-sufficiency, thousands of cadres defected across the border and joined Vietnamese forces, which invaded Cambodia in December 1978. They drove the remnants of the Khmer Rouge into the jungle along the border with Thailand, where they resumed their former campaign of guerrilla warfare.

The fighting created an immediate refugee emergency that became embroiled in Cold War politics. Aid from western governments ended up backing the Khmer Rouge campaign against the Moscow-backed Vietnamese government in Phnom Penh.

Faced with diminishing support as the Soviet Union disintegrated, the Vietnamese eventually withdrew in 1989 and a power-sharing arrangement was set up between a United Nations transitional authority and representatives of the various factions ahead of elections scheduled for 1993. The United Nations Transitional Authority in Cambodia (UNTAC) cost $1.9 billion, making it the most expensive peacekeeping operation in U.N. history.

Although the Khmer Rouge continued to launch guerrilla attacks, killing civilians and planting hundreds of thousands of landmines, their movement began to fall apart amid mass defections, spurred by a government amnesty in 1994.

Pol Pot was eventually deposed by his remaining henchmen in 1997 and placed under house arrest in a rebel-held area. He died on April 15, 1998.

Cambodia's prime minister is Hun Sen, who has been in power in various coalitions for over two decades. A former Khmer Rouge guerrilla who lost an eye in Pol Pot's assault on Phnom Penh in 1975, Hun Sen became the world's youngest prime minister in 1985, leading the Vietnamese-backed government when he was just 33.

King Sihanouk was restored as Cambodia's constitutional monarch under the U.N.-brokered peace pact in 1991.

Elections in 1993 led to a coalition dominated by Hun Sen's Cambodian People's Party (CPP) and the royalist FUNCINPEC party's Prince Norodom Ranariddh, Sihanouk's son.

But power-sharing collapsed in 1997, when Hun Sen seized power in a coup which drew international condemnation.

Elections the following year were won by the CPP and another coalition was formed, with Hun Sen as prime minister and Ranariddh as president of the National Assembly.

Hun Sen's party won elections again in 2003, but failed to secure a majority. The country was deadlocked for a year until the premier forged another coalition agreement with FUNCINPEC.

FUNCINPEC has since dropped Ranariddh as its leader. In 2007, he was sentenced in absentia for embezzlement in a case brought against him by former party colleagues. He now lives in Malaysia.

Hun Sen's party claimed victory again in elections in 2008, although European Union monitors said the vote fell short of international standards.

Khmer Rouge trials

It has taken years of negotiations to establish a tribunal to try former leaders of the Khmer Rouge, a delay that has blighted Cambodia's international reputation.

The courtroom and administrative offices of the U.N.-backed Special Tribunal finally opened in a military complex just outside Phnom Penh in early 2006, 27 years after the regime was driven from power.

Cambodian and international judges agreed in June 2007 on the underlying rules for the special court to try Pol Pot's top surviving henchmen.

A month later, the first formal charges of crimes against humanity were laid against Kaing Guek Eav, nicknamed Duch, former commander of the notorious Tuol Sleng interrogation and torture centre. His trial began in February 2009.

In September, authorities arrested and charged Khmer Rouge "Brother Number Two" Nuon Chea, Pol Pot's top surviving henchman. The octogenarian had been living as a free man since cutting a deal with Phnom Penh in 1998. Having confessed to mass murder, Duch is expected to be a key witness against Nuon Chea.

Also under arrest are ex-president Khieu Samphan, former foreign minister Ieng Sary and his wife Khieu Thirith.

Military chief Ta Mok died in 2006. Most Cambodians saw his death as an escape from justice, reviving fears that senior Khmer Rouge members would die before facing the tribunal.

The court has been plagued by delays and arguments between local and international legal officials. Critics say that the process will not meet international standards, given its unusual mixed structure that will include local judges and prosecutors, often criticised as corrupt, weak and lacking in independence.

The United Nations had initially wanted a panel of exclusively international judges sitting outside Cambodia to run the tribunal. The Cambodian government originally demanded Cambodian judges only. But a compromise was reached in 2001 on the hybrid formula, which stipulates three Cambodian and two foreign judges.

In 2008, the court asked donors for an additional $114 million on top of its initial $56 million budget.

Poverty and aid

International donor governments and institutions agreed in 2007 to give Cambodia $690 million in grants and loans, up from $601 million 2006 and $504 million in 2005.

The Cambodian government, which relies on foreign aid to cover as much as 60 percent of its spending, described the huge increase as a "reward" for the country's good performance in reforming its economy.

The World Bank says the number of Cambodians living under the poverty line has dropped, but that the benefits of growth have been spread unevenly, resulting in a rise in inequality.

Economic growth has been largely limited to urban centres and the income gap between rich and poor remains a serious problem.

Donors have called for greater commitment to reform of a notoriously corrupt and political judiciary, and swift enactment of draft anti-graft laws that have been gathering dust on the shelves of parliament for years.

Activists say that donor calls for political reform carry little weight given the continuing disbursement of vast sums of aid money, which they say sends completely the wrong signal to a government that continues to harass and intimidate human rights defenders, opposition party members and journalists.

Campaigners also say that huge amounts of aid are wasted on so-called Technical Assistance (TA), namely expensive foreign consultants who are drafted in to advise recipient governments.

"There has been no systematic analysis of the effectiveness of TA in Cambodia," the advocacy group ActionAid said in a 2005 report.

According to the report, some $1.2 billion was spent on TA between 1999 and 2003. In 2002, the aid spent by donors on some 700 consultants amounted to between $50 and $70 million, roughly equivalent to the wage bill of 160,000 Cambodian civil servants, who earn as little as $25 a month.

Donors have promised aid worth $951.5 million for 2009 - the most since 1994, even though some have expressed concern over the government's plan to double spending on the military next year to $500 million after a border clash with Thailand in 2008.

Landmines

Landmines continue to represent one of the most destructive legacies of Cambodia's violent past. Estimates vary, but it is believed that there are between four and six million landmines in Cambodian soil.

According to the United Nation's Electronic Mine Information Network, close to half of all villages are affected, with a suspected contaminated area of almost 4,500 square kilometres.

Today, one-third of the victims are children in the countryside. This brings the number of mine victims-killed, injured or disabled-in Cambodia to more than 60,000. Amnesty International says many of the victims are poor people seeking land who have moved into affordable areas yet to be de-mined.

HIV/AIDS

Numerous factors render Cambodia particularly vulnerable to HIV/AIDS. Decades of conflict combined with chronic poverty and political turmoil have led to a weak health infrastructure that struggles to care for all those living with the disease.

According to UNAIDS, AIDS-related diseases have already killed more than 80,000, primarily from heterosexual sex, and the government expects the death toll to reach 230,000 by 2010. There are also more than 50,000 AIDS orphans.

Yet having suffered one of the highest infection rates in Asia, the country has begun to see some success in its fight against the epidemic. After peaking at 3 percent in 1997, national adult HIV prevalence in Cambodia fell to 1.6 percent in 2005, according to the UNAIDS/WHO 2006 AIDS epidemic update.

At the heart of the success was the government's decision to order all brothels, which are legal in Cambodia, to require sex workers to insist on the use of condoms. But UNAIDS warned in 2007 that men were increasingly turning to so-called indirect sex workers, women who informally sell sex outside brothels, with whom they are less likely to use a condom.

Officials warn that HIV/AIDS still has the potential to impede significantly the social and economic development of the country.

Bird Flu

The first case of bird flu in Cambodia was confirmed by the government in January 2004. As of early 2009, seven Cambodians had died of the virus.

See our bird flu briefing for more.