Later we drove to a bluff above the Royal Tombs, on the Perfume River. 'That's VC territory,' said Mr McTaggart, the local USIS official. He was a genial white-haired man, who cooked his own meals and sometimes rode his bicycle out here and practised his Vietnamese with the sentries on the bluff. Across the river, the Viet Cong territory was a number of scalped hills: it had been defoliated. But there was still shooting now and then. An ARVN boat would chug close to the enemy bank and spend an afternoon firing into the hills, not at a particular target, but more like the French man-of-war in Heart of Darkness that aimlessly – insanely, Conrad says – shells the African jungle. I must come during the hot season, one of the Vietnamese said. Then I could hire a boat and a girl and bring some food, and I could spend a night on the river like this, making love and eating where it was cool.

I promised I would. We went to the tombs next. The older the buildings were in Hue, the better their state of preservation: last year's Quonset huts were falling to bits, Mr McTaggart's forty-year-old house was seedy but comfortable, the hundred-year-old Royal Tombs were in very good shape, although these had been made with second-hand materials, in accordance with Vietnamese custom (to stress humility) – old lumber and stone, broken pottery, and cracked tiles. There were tangled gardens and carved gateways with panting dragons crouched over the arches; and in the interior rooms, the dusty mausoleums, ancient women hobbled from artifact to artifact, lighting tapers to show us the French clock (its hands missing), the crystal candelabra, the gilt altars and the cabinets inlaid with mother-of-pearl, the peacock fans with moulting feathers ('She says they're from the French king'). The hands of the old ladies trembled as they held the flames of the tapers close to the tinder-dry treasures, and I was afraid they'd set the place alight. When we left they blew out all the candles and remained in the dark tombs. It was a city people were constantly fleeing, but here in the tombs the old ladies -retainers to kings of the twenties and thirties – never left. They ate and slept in the precincts of the royal mausoleum.

It was cold that night; dogs barked in the muddy lane, and in spite of the chill my bedroom was filledwith tormenting mosquitoes.

At Hue Station the next morning a tiny Vietnamese man in a grey gaberdine suit and porkpie hat rushed forward and took my arm. 'Welcome to Hue,' he said. 'Your carriage is ready.' This was the stationmaster. He had been notified of my arrival and had shunted on to the Danang passenger train one of the director's other private cars. Because Vietnam Railways has been blown to pieces, each separate section has a director's car on one of its sidings. Any other railway would have one such car, but Vietnam Railway is six separate lines, operating with laborious independence. As at Saigon, I boarded the private coach with some misgivings, knowing that my hand would tremble if I ever wrote anything ungenerous about these people. I felt loutish in my empty compartment, in my empty coach, watching Vietnamese lining up to buy tickets so that they could ride in overcrowded cars. The stationmaster had sped me away from the ticket window ('It is not necessary!'), but I had caught a glimpse of the fare: 143 piastres (twenty-five cents) to go to Danang, perhaps the cheapest seventy-five-mile ride in the world.

Dial, the translator, and Cobras One and Two boarded and joined me in the compartment. We sat in silence, peering out the window. The blocky whitewashed station building, a version of the Alamo, was riddled with bullet holes that had broken off pieces of the stucco, revealing red brickwork beneath. But the station, the same vintage as McTaggart's bay-windowed villa and the Morin Brothers' shop, had been built to last – a far cry from the patch of wasteground and cement foundations just outside Hue, where the First Marine Division's collapsed barracks and splintered obstacle course lay sinking in the mud. It was as if all the apparatus of war had been timed to self-destruct the day the Americans pulled out, leaving no trace of the brutal adventure behind. In the train yard, several armoured vans showed rips in their steel sides where mines had punched them apart. These vans were the homes of a number of sad-looking children. In most tropical countries adults stand, like those posed by William Blake, at the fringe of the echoing green, watching children at play. In Vietnam the children play alone, and the adults appear to have been swept away; you look for the parents among large groups of children, for the background figure of an adult. But (and this distorts the landscape) they are missing. That old woman carrying a child on her back, with the long muddy skirt and rain-drenched hair, is another child.

'Have you see the sink in the w.c.?' asked Dial.

'No.'

'You turn on the tap and guess what comes out?'

'Rust,'I said.

'Nothing,' said Cobra Two.

Dial said, 'Water!'

'Right,' said Cobra One. 'Paul, take that down. The taps work. Running water available. What do you think of that?'

But this was the only sink in the train.

The stationmaster had said that the line to Danang had been open for four months, having been out of action for five years. So far there had been no recent disruptions. Why its reopening coincided with the American withdrawal no one could explain. My own theory was that there were now no American trucks plying back and forth along the only road that goes between Hue and Danang, Highway One, the poignantly named 'Street without Joy'; this shrinking of expensive road traffic had forced the Vietnamese into the more sensible course of opening the railway. The war had become not smaller, but less mechanized, less elaborate. Money and foreign troops had complicated it, but now the Vietnamese had reverted from the corporation-style hostilities of the Americans to the colonial superstructure, slower communications, a return to farming, housing in the old buildings, and a transport system based on the railway. The American design of the war had been abandoned -the empty firebases, the skeletons of barracks, and the torn-up roads showed this to be a fact, visible from the passenger train clanking towards Danang with its cargo of Hue-grown vegetables.

The bridges on that line speak of the war; they are recent and have new rust on their girders. Others, broken, simulating gestures without motion, lay beyond them where they had been twisted and pitched into ravines by volumes of explosives. Some rivers contained masses of broken bridges, black knots of steel bunched grotesquely at the level of the water. They were not all recent. In the gorges where there were two or three, I took the oldest ones to be relics of Japanese bombing, and others to be examples of demolition from the later terrorism of the fifties and sixties, each war leaving its own unique wreck. They were impressively mangled, like outrageous metal sculptures. The Vietnamese hung their washing on them.

It was at the rivers – at these bridges – that soldiers were most in evidence. These were strategic points: a bombed bridge could put the line out of action for as long as a year. So at each side of the bridge, just above it on outcrops of rock, there were igloos of sandbags, and pillboxes and bunkers, where sentries, most of them very young, waved to the train with carbines. On their shelters were slogans flying on red and yellow banners.

Dial translated them for me. A typical one was, GREET THE PEACE HAPPILY BUT DON'T SLEEP AND FORGET THE WAR.

The soldiers stood around in their undershirts; they could be seen swinging in hammocks; some swam in the rivers or were doing their washing. Some watched the train, with their rifles at their shoulders, in those oversize uniforms – a metaphor of mismatching that never failed to remind me that these men – these boys – had been dressed and armed by much larger Americans. With the Americans gone the war looked too big, an uncalled-for size, really, like those shirts whose cuffs reached to the soldiers' knuckles and the helmets that fell over their eyes.