Before I left the office, Mr Chau took me aside. 'Don't go to Bien Hoa by train,' he said.

I asked him why.

'That is the worst train in the world,' he said. He was embarrassed that I should want to take it.

But I insisted, and, wishing him well with his campaign to attract tourists to the battlefields, I set off for the station. There is no sign on Saigon Station, and, though I was perhaps fifty feet away from it, no one in the area knew where it was. I found it purely by chance, cutting through an Air Vietnam ticket office, but even when I got on the platform I was not sure it was the railway station: there were no passengers and no trains at the platform. The train, it turned out, was a short distance up the line, but it was not due to leave for twenty minutes. The carriages were battered green boxes, some wooden (with protruding splinters) and some metal (with dents). The seating arrangements, a narrow bench running along the walls of the carriage, were neither comfortable nor convenient, and most of the passengers were standing. They smiled, clutching their very discouraged ducks and chickens and their cruelly sunburned half-American infants.

There was another even older train parked on the far side of the yard. Attracted by the wrought-iron railings on the porches – a French feature of the car – I sauntered over. I climbed into this semiderelict train and heard a sharp howl of complaint. A girl jumped up two cars away (I saw her figure framed by the broken doors) and pulled on a pair of jeans. Then I saw a boy fussing with his clothes. I started off in the opposite direction and ran into two sleeping heroin addicts, both pimply girls with tattoos and needle scars on their arms. One woke and shouted at me. I hurried away: there were other lovers on the train, and children, and menacing-looking youths poking through the cars. But the train had no engine: it wasn't going anywhere.

The stationmaster, wearing a plastic-visored cap, crossed the track, waving to me. I hopped out of the derelict train and went over to shake his hand. Laughing sheepishly, he explained that it was not this train that was going to Bien Hoa but that one, and he pointed to the line of bulging boxcars. I headed for one of the cars and was about to swing myself up when the stationmaster called out, 'No! No!'

He motioned for me to follow him, and, still laughing, he led me to the tail end of the train, where there was quite a different sort of railway car. This wooden carriage, with a kitchen and three sleeping compartments and a large lounge, was obviously a relic from the Transindochinois, and, though it was not luxurious even by Indian standards, it was comfortable and spacious. It was, said the stationmaster, the director's: the director had requested that I ride in it. We got in; the stationmaster nodded to the signalman, and the train started up.

A free ride in the director's personal railway car, to confound the unreality of the place still further: it was not what I expected – not in Vietnam. But this emphasis on privilege is a version of American extravagance. It is a function of the war, which produced an obliging system for conditioning the sympathy of visitors, all of whom (for the risks they believed they were taking) wanted to be treated like VIPs. Every visitor was a potential publicist, the irony being that even the most furious dove was afforded the unlimited credit and comfort on which he could preen his sensibilities into outrage. This hospitality, heightened by the natural generosity of the Vietnamese, continues. It was almost shameful to accept it, for it had its origins in the same plan a company develops when it cynically mounts a campaign to popularize an unsuccessful product. It distorted the actual. But I reserved my scorn: the Vietnamese had inherited cumbersome and expensive habits of wastefulness.

We sat around the table in the lounge that took up a third of the director's carriage. The stationmaster put his cap away and smoothed his hair. He said that after the Second World War he had been offered a number of well-paying jobs, but he chose instead to go back to his old job on the railway. He liked trains and he believed Vietnam Railways had a great future. 'After we reopen the line to Loc Ninh,' he said, 'then we go to Turkey.'

I asked him how this was possible.

'We go up to Loc Ninh, then we build a line to Phnom Penh. That goes to Bangkok, no? Then somewhere, somewhere and somewhere – maybe India? – then Turkey. There is a railway in Turkey.'

He was certain Turkey was just over the hill, and the only difficulty he envisaged – indeed, it seemed a characteristic of the South Vietnamese grasp of political geography – was getting Loc Ninh out of the hands of the Viet Cong and laying track through the swamps of Cambodia. His transcontinental railway vision, taking in eight vast countries, had a single snag: evicting the enemy from this small local border town. For the Vietnamese citizen the rest of the world is simple and peaceful; he has the egoism of a sick man, who believes he is the only unlucky sufferer in a healthy world.

The stationmaster said, 'Sometimes we get ambushed here. A few weeks ago some four people were killed by rifle fire.'

I said, 'Perhaps we should close the windows then.'

'Ha! Very good!' he said, and translated the joke for his deputy, who was setting out glasses of Coca-Cola.

It was a single-line track, but squatters had moved their huts so close to it, I could look into their windows and across rooms where children sat playing on the floor; I could smell the cooking food – fish and blistering meat – and see people waking and dressing; at one window a man in a hammock swung inches from my nose. There was fruit on the window sills, and it stirred – an orange beginning to roll – as the train sped by. I have never had a stronger feeling of being in the houses I was passing, and I had a continuous sense of interrupting with my face some domestic routine. But I was imagining the intrusion: the people in those poor houses seemed not to notice the strangers at their windows.

From the back of the train I could see the market women and children reoccupying the track, and once – a swift sight of a leaping man – I thought I saw an American, in beard and flapping pyjamas, tall, light, round-shouldered, but with large revealing feet and a long stride. He disappeared between two tottering wooden buildings and was enclosed by lines of faded laundry. This was in one of the most crowded slums in the Saigon outskirts, and the glimpse of this man, who was the wrong size for the place – his ungainliness emphasizing his height over all the others – made me inquire about him later. Dial told me he was probably a deserter, one of about two hundred who remain in the country, mainly in the Saigon area. Some are heroin addicts, some work at legitimate jobs and have Vietnamese wives, and some are thugs – much of the breaking and entering in Saigon is attributable to the criminally versatile deserters: they know what to take at the PX; they can steal cars with greater anonymity than the Vietnamese. None of these men has identity papers, and Vietnam is a hard country to leave. Their only hope is to take a boat up the Mekong and cross into Thailand; or they could surrender. It was an odd community of practically nameless fugitives, and the idea of them – of that bearded man in pyjamas crossing the track on that very bright day, briefly exposed – filled me with curiosity and pity in the same degree. I saw in them a fictional possibility, a situation containing both a riddle and some clues for solving it. If one were to write about Vietnam in any coherent way one would have to begin with these outsiders.

I left the private car and moved through the train. It was filled with horribly mutilated people, amputees with rounded stumps, soldiers in wrinkled uniforms, and old men with stringy beards, leaning on walking sticks. A blind man wearing a straw Stetson was playing a guitar and singing tunelessly for a group of soldiers. But it was not entirely a train of decrepit and abandoned people. The impression I had on the train to Bien Hoa, one that stayed with me throughout my time in Vietnam, was of the resourcefulness of the Vietnamese. It seemed incredible, but here were schoolgirls with book bags, and women with huge bundles of vegetables, and men with trussed fowl, and others, standing at the doors of what were essentially freight cars, off to work in Bien Hoa. After so many years one expected to see them defeated; the surprise was that they were more than survivors. From the cruel interruptions of war they had stubbornly salvaged a routine: school, market, factory. At least once a month the train was ambushed, and 'the offensive' was spoken about with the tone of inevitability people use about monsoons. But these passengers made their daily trip. It was a dangerous journey. They were resigned to danger. For them life would never change, and the menace of the enemy was as predictable and changeless as the weather.