Cambodian prime minister Hun Sen has become a “fully fledged military dictator” according to Human Rights Watch in a report released on Thursday investigating the extent of his personal control over the military and the police.

The new report, Cambodia’s Dirty Dozen, names the 12 military personnel who have been the “backbone” of Hun Sen’s “abusive and authoritarian political regime,” which he has led since 1985. According to the report, Hun Sen has “remained in power by creating a cadre of ruthless members of the security forces to implement his vision and orders”.

While Hun Sen while has always been notorious for his autocratic rule – his official title is princely exalted supreme great commander of gloriously victorious troops – and his use of force against anyone who defied him, his crackdown on the opposition, the media and civil society has escalated in the past year in the build up to elections in July.

“Hun Sen really has become a fully-fledged military dictator, a fact that he hopes to hide behind the fig-leaf of a national election in July that will be neither free nor fair,” said Phil Roberton, deputy director of Human Rights Asia.

Last year Hun Sen dissolved the opposition party, the CNRP, shut down the Cambodia Daily newspaper, Radio Free Asia and dozens of local radio stations. Journalists, opposition politicians and civil society leaders are now in jail and an atmosphere of fear and self-censorship has gripped the country.

Hun Sen was able to carry out the brutal crackdown in less than six months without any backlash, because of his control over 12 senior military and police commanders and their subordinates. Twelve different institutions, from the supreme court, to local courts and government ministries, were used to implement the crackdown.

With no legitimate opposition, Hun Sen’s victory in the elections is now seen as a foregone conclusion.

“What this report reveals is the deep military roots that characterise Hun Sen’s rule,” said Roberton. “At each step of the way in his years in power, Hun Sen has sought to centralise control over the military and police under his direct command, aided by this group of dangerous men.”

Many of this group of 12 – which includes General Pol Saroeun, supreme commander of the royal Cambodian armed forces and General Neth Savoeun, supreme commander of the Cambodian national police – served in the Khmer Rouge military with Hun Sen, the Communist regime which saw the execution, starvation, and disease of an estimated 1.2 to 2.8 million Cambodians (between 13 and 30% of the population) between 1975 and 1979.

The Human Rights Watch report lays out how most of these men have been “implicated in the use of unnecessary, excessive, and sometimes lethal force against protesters” and have been involved in “non-political abuses against the ordinary population, such as land-takings, murder, torture, and arbitrary detention.”

The complete absence of separation between military and politics is seen in the fact that hundreds of police and military now sit on the central committee of Hun Sen’s party, and that Hun Sen’s bodyguard unit – a military force personally under his control and out of the usual chain of command – went from having around 60 people in it in the mid-1990s, to having around 23,000 soldiers by 2015, according to Lee Morgenbesser, an expert on authoritarian regimes in southeast Asia.

Hun Sen’s crackdown, carried out when he feared the opposition was gaining too much popularity in the lead up to the election, was made possible by broader international circumstance.

China is investing billions into Cambodia as part of its belt and road initiative, and is willing to back Hun Sen’s authoritarian regime; they have already declared that the election in July will be “free and fair”.

The Trump administration in the US are also no longer holding the regimes in Cambodia and Vietnam to account over human rights abuses, as happened under President Obama.

“To put it simply, this American administration don’t care about human rights and democracy in southeast Asia and that gave a pretext for Hun Sen’s crackdown,” said Morgenbesser. “The game has changed now . He almost doesn’t need to feign legitimacy to the US administration anymore about this election being ‘democratic’ – no one there is paying attention anymore.”

Hannah Ellis-Petersen South-east Asia correspondent