Cambodian government officials and pro-government media yesterday commemorated the seldom-observed anniversary of Marshal Lon Nol’s rise to power, seizing the opportunity to once again re-litigate historical grievances with the United States.

In an article on Sunday, Lim Cheavutha, the CEO of government mouthpiece Fresh News, pointed to the takeover, through which the general seized power from then-Prince Norodom Sihanouk, as directly linked to US backing and the subsequent Khmer Rouge atrocities.

“On March 18, 1970, 48 years ago, the decision of the politician Lon Nol and Prince Sisowatch Sirik Matak, with strong support from the US, to do a coup to overthrow Prince Norodom Sihanouk, caused casualties to the nation and Cambodian people, including acts of genocide,” Cheavutha wrote, before saying the nation was “liberated” by the ruling Cambodian People’s Party.

While Sihanouk was abroad in Europe that month in 1970, anti-Vietnamese protests erupted in the capital. Lon Nol went over the head of Sihanouk – who had tolerated Vietnamese Communists within Cambodia – ordering the Vietnamese to leave the country within 72 hours.

Some reports claim that his deputy, Prince Sisowath Sirik Matak, was the true orchestrator of the coup, convincing Lon Nol to take power. On March 18, the National Assembly voted almost unanimously to remove Sihanouk, installing Lon Nol as the head of state of the new Khmer Republic, which would then be heavily supported by the US government.

Cheavutha’s rhetoric on Fresh News was echoed by hardline party supporters Heng Ratana and Phay Siphan, who took to Facebook to mark the historic day. On Monday, Ratana, head of Cambodia’s demining body, also claimed the coup led directly to the rise of the Khmer Rouge and the subsequent deaths of more than a million Cambodians, while posting a picture on social media of a US bomber.

Government spokesman Siphan, meanwhile, shared posts from a third party that provided alleged evidence of US involvement in the coup and claimed the incident forced Cambodia to become embroiled in the Vietnam War.

However, pre-eminent historian David Chandler questioned the validity of this version of events. “Scholars have searched in vain for American involvement in the coup, which was staged not by Lon Nol but by the National Assembly,” he said via email.

Chandler added that North Vietnam’s presence in Cambodia and Sihanouk’s own alliance with the Khmer Rouge were both more major factors in thrusting Cambodia into the Vietnam War.

Despite this, Chandler said America’s role was not passive, with the superpower welcoming the rise of the Lon Nol regime, supporting it once in power and attempting to use it to its benefit. “Nixon thought for reasons that elude me that Cambodia was the key to winning the Vietnam War,” he said.

Ear Sophal, associate professor of diplomacy and world affairs at Occidental College, said Lon Nol’s coup was done with “far fewer mortars, bombs, and tanks” and “certainly fewer deaths” than Hun Sen’s own 1997 power grab, in which he ousted First Prime Minister Norodom Ranariddh.

“The US, as with many coups elsewhere, did not object to the coup. That does not mean they were behind it,” Sophal said. He added that they may have known about it in advance, but that was “not the same as orchestrating it”.

He also said the rhetoric surrounding the anniversary appeared to be an attempt to drum up more anti-American sentiment in a crucial election year. That rhetoric – of the US and much of the West meddling in Cambodian affairs – has been used to justify a crackdown on the opposition party, civil society and the media.

“They’re throwing the kitchen sink at July 2018,” Sophal said, referring to the elections.

The US war legacy in the country has been especially criticised, with government officials repeatedly raising the presence of unexploded ordnance and mines and calling for forgiveness of debt owed to the US from the Lon Nol era, all while the US has withdrawn aid and imposed visa sanctions in response to the crackdown on the opposition.

“Phnom Penh would do well to remember that there are no permanent friends or enemies, only permanent interests. Is it in the permanent interest of Cambodia to be anti-American? I don’t think so,” Sophal said.

Additional reporting by Ben Sokhean