It was in the canteen car of the late-night service that the Vietnam veteran finally told me his story. We’d been friends for months, regulars at a Louisiana-themed bar off Saigon’s Bùi Viện backpacker strip, but his time in-country was, if not exactly taboo, not really a go-to topic, either.

A haze of railway employees’ cigarette smoke hung in the air, mingling with the steam from their bowls of phở. We were heading north to Quảng Ngãi, smack-bang in the middle of the country on the coast, where we were scheduled to take a car into the mountains and visit an orphanage for children of the Bahnar indigenous minority. Perhaps it was the fact that we were talking one-on-one for the first time, or perhaps it was the sheer volume of beer we’d consumed over the course of the evening – the better, we reasoned, to rock us to sleep. Either way, the vet decided it was time I learned a thing or two.

The story that unfolded was right out of Michael Herr’s Dispatches, an un-filmed sequence of Apocalypse Now conveyed orally, in equal parts surreal and evil. What surprised me was how unsurprised I was by it all. The weirdest thing about this country’s weirdness is how rapidly it ceases to be weird. When the strange and the mad become par for the course, one quickly learns to adjust one’s swing.

The vet was flown into Đà Nẵng in 1970, where, to his surprise, he was plucked from his unit, the guys he had trained with, and sent north on his own. Whatever his friends would go on to do in the war, the powers that were had something different in store for him. ‘Probably because I was stupid,’ he said. ‘And they knew I wouldn’t ask any questions.’ After being shuttled about from one place to another, his mission always ahead of him somewhere – at the next landing zone, the next firebase – he found himself perilously close to the DMZ, where he was to serve out his tour with a unit whose name I’m going to keep to myself.

He arrived in fine weather to find a North Vietnamese soldier hanging dead from a tree.

‘What the hell’s going on here?’ he asked.

‘Interrogation,’ someone told him.

‘Can’t imagine he’s going to tell you anything now.’

‘No,’ the welcoming party admitted. ‘But there are two more inside who might.’ He was given the skull of a dead Việt Cộng, which the unit had ‘found’ during the 1968 Tết Offensive and repurposed as a candle, and told to hold onto it until the next FNG rocked up. He’d only been in camp for five minutes and already everything was FUBAR.

I excused myself to a foul-smelling toilet cubicle to get some of this down on a scrap of serviette, the pen skipping across the flimsy paper, occasionally piercing it as the train threatened to come off the rails at speed. I was doubtless standing in someone’s splashback. I returned without mentioning what I had been doing to be told the terrible story of the mercenaries.

They were Taiwanese, the vet told me as he ordered another beer, murderers and rapists with life sentences on their heads who had been promised amnesty by the CIA in return for fighting America’s war. They would be flown into villages done up in black pyjamas, wreak havoc in a manner to which they were uniquely suited, and then flown out so the spooks could go in, cluck their tongues a bit and proclaim: ‘This is why you need to side with us against the Communists.’

The vet became thick with a couple of these guys – he’d take them beer in their section of the camp – and was aware that they weren’t exactly enjoying their vacation. Those of their number who had been dropped into North Vietnam only rarely returned and the fact hadn’t been lost on them for a second. Eventually, they rioted, turned their guns on their keepers, and the entire American contingent of the base was flown out to China Beach on mandatory R&R. When they returned, the problem had been – how to put it? – dealt with. ‘They never did get that amnesty,’ the vet said.

What does one do with a piece of information like this? It’s practically impossible to confirm: no military official will ever do so, Google turns up nothing of value – the unit’s unofficial website is noticeably mum on specifics – and even a search of the dark web proves futile. The legendary war photographer Tim Page briefly mentions America’s use of Chinese mercenaries in his autobiography, Page After Page, which I bought in its illegal, photocopied form from a Saigon street vendor, describing them as ‘a hardcore reaction force, recruited off the streets and out of jails.’

‘These troops were mean and hunted VC for money,’ Page writes, ‘cash for heads, piastres for weapons captured. They had no regard for the Geneva Conventions. . . . An expendable, non-partisan force, owing allegiance only to its paymaster.’

The Taiwanese mercs, the vet told me, while waiting for their amnesty, were paid primarily in enemy ears, which they wore, like the scalp-collecting marauders of Cormac McCarthy’s Blood Meridian, on strings around their necks. But the correlation between Page’s story and the vet’s is hardly enough to back up claims of either. Hardly enough for a work of hard-nosed reportage, a shocking exposé, a book. Does one sit on the information? Filter it into a fictionalised account with poetic license on hand as a ready defence against military denial or worse? (I have already done that with other aspects of the vet’s story.) Or does one offer it up, as I have tried to do here, as little more or less than what one was told, hearsay to fall or stand on its merits in the marketplace of ideas? This is what I was told. Let others have at it.

It was not until he left the country that the vet began to wonder about what he had been involved in here. He might never have questioned it, assuming that everyone in-country had worked in similarly dark shadows, had it not been for the unsettling nature of his debrief. ‘Never tell anyone what you saw here,’ he was told. ‘We have ways of making examples of you all.’

This throws up other complications for someone like me. Have I identified my vet too much? Do American military and intelligence types read Overland that regularly? (Actually, now that I think about it. . .) Do they care anymore about what the vet saw and did here? One can never be too sure, especially when talking, not about ‘normal’ atrocities like the Mỹ Lai massacre, but about Air America, Laos and Cambodia, the spook war. (‘Don’t talk to me about Mỹ Lai,’ the vet said before our trip, when a friend at the bar pointed out that it would take us close to the site of the massacre. ‘Four hundred, five hundred people? That’s nothing.’) In my defence, I eventually wound up taking notes in front of the vet, using the wooden table to smooth out the serviettes. He knew what I was doing. He rolled his eyes and ordered another beer. ‘I don’t give a shit anymore,’ he told me.

Of course, when we awoke the next morning, somewhere north of Nha Trang, sunlight dappling our sleeper compartment through too-thin curtains as a steward spruiked coffee somewhere further down the carriage – ‘Cà phê đen! Cà phê sữa đá!’ – the vet’s stories of the night before went unmentioned. Actually, we didn’t speak much at all. The vet’s eyes spoke loudly enough on their own. Hope you got down what you needed, son. Closing the vault now. One-time offer. See you back in the world.