On 17 April 1975 Khmer Rouge units entered Phnom Penh and ordered all residents to leave the city. It was the beginning of Cambodia's nightmare – and one of the worst genocides in human history. Wilfred Burchett, like so many commentators in the West, initially hailed the victory of the Sihanouk–Khmer Rouge alliance and treated with scepticism reports of atrocities in Cambodia. But he was not allowed into ‘liberated’ Cambodia and his lines of communication with his old friend Sihanouk were cut off.

He first became convinced of the murderous nature of the Pol Pot regime when investigating Khmer Rouge incursions along the Cambodia–Vietnam border. He is still often accused of ongoing support for the Khmer Rouge, but he immediately reported on the true nature of the regime as soon as he was afforded the opportunity to witness the situation with his own eyes – thus maintaining his interest always to report ‘on the spot’. He was one of the first Western journalists on the Left to correct the record, and his book on this subject, The China Vietnam Cambodia Triangle, demonstrates clearly that he was in fact one of the most important denouncers of the Khmer Rouge regime.