Almost before I realised what was happening there were no more civilians on the train; only officers and men and the train crew. All the carriages were armoured; we had three armour-plated diesel locomotives in front and another two behind, there were anti-aircraft flat cars every three or four carriages, covered wagons holding field guns and howitzers, a radio car with its own generator, several flat cars with tanks and staff cars and artillery tractors, many conscript-crammed barrack cars, and a dozen or so wagons full of oil drums.

I now served only officers. They drank more and tended to damage things, but were less likely to throw cutlery if one dropped dirty plates.

The sunlight grew less, the winds colder, the clouds darker and thicker. We passed no more refugees, only the ruins of towns and villages; they looked like charcoal sketches: the black of soot-covered stones and the empty white of clinging snow. There were army camps, sidings full of trains like ours, or trains with hundreds of tanks on flat cars, or gigantic guns on articulated many-axled cars the length of half a dozen ordinary wagons.

We were attacked by planes; the anti-aircraft platforms crackled with noise and sent clouds of acrid smoke drifting down the side of the train; the planes attacked with cannon shell, smashing windows. Bombs missed us by a hundred yards. I lay on the floor of the galley with the chief steward, hugging a box of finest crystal glasses while the windows splintered around us. We both stared in horror as a wave of red liquid spilled from round the galley door, thinking one of the chefs had been hit. It was only wine.

The damage was repaired; the train rolled on, into low hills under dark clouds. The hills were blown clear of snow in places, and though the sun now never rose very far in the sky, the air became warmer. I thought I could catch the breath of the ocean; sometimes there was a smell of sulphur. The army camps grew larger. The hills gradually became mountains, and I saw the first volcano one night while serving dinner; I mistook it for some terrible night attack in the distance. The soldiers gave it only the most cursory glance and told me not to spill the soup.

There were distant explosions all the time now; sometimes volcanic, sometimes man-made. The train rolled and whined over newly repaired track, crawling past long lines of grey-faced men with sledgehammers and long shovels.

We ran from attacking planes; dashing along straights, hurtling round bends - carriages tipping sickeningly - then plunging into tunnels, braking furiously, everything clattering and crashing^ the tunnel walls flashing with the light from our howling brakes.

We off-loaded tanks and staff cars, we took on wounded; the debris of war was scattered over these hills and valleys like rotting fruit in an abandoned orchard. Once, at night, I saw the glowing remains of tanks caught in a ruby-red flow. The lava rolled down the valley below us like burning mud, and the wrecked tanks - tracks undone, gun barrels tilted crazily into the air - were borne down on that incandescent tide like strange products of the earth itself; infernal antibodies in that red stream.

I still served the officers their meals, though we had no wine left and our supplies of food were reduced both in quantity and quality. Many of the officers who had joined the train after we entered the battle zone would stare at their plates for minutes at a time, gazing incredulously at what we'd put before them, as confused and disturbed as if we'd just ladled a bowlful of nuts and bolts onto their plates.

Our lights blazed all day; the dark clouds, the vast rolling billows of volcanic smoke, the low sun which we could go days at a time without seeing; all consipired to turn the wreckage-strewn mountains and valleys into a land of night. All was uncertainty. A horizon of deeper darkness might be raincloud or smoke; a layer of white on a hillside or plain might be snow, or ash; fires above us might be burning hill forts or the side vents of great volcanoes. We travelled through darkness, dust and death. After a while it began to seem quite natural.

I believe that if we had gone on, the train - lava-spattered, dust-caked, dented and patched - would have accumulated so much cooled lava on its carriage roofs that from above at least it would have had a form of natural camouflage of rock; an evolved skin, a protective layer grown in this harsh place, as though the metals of the train's own articulated body were spontaneously returning to their original forms.

The attack came in the midst of fire and steam.

The train was descending from a mountain pass. In a shallow valley to one side a loose lava flow ran rapidly, almost keeping pace with the train. As we approached a tunnel through a spur of rock, a vast rising veil of steam reared in front of us, and a sound like a gigantic waterfall slowly drowned out the noise of the train. On the far side of the mist-filled tunnel, we saw that a glacier was blocking the lava flow's way: the ice sheet extended from a side valley, its soiled meltwaters feeding a broad lake. The lava had spilled into the lake, forcing a huge steaming wave of water-cooled debris in front of it.

The train rolled hesitantly forward towards another bank of thick mist. I was making beds in one of the sleeping cars. When the first small rocks started to roll down the mountainside I left that side of the carriage and watched through an open door as larger and larger boulders came crashing down the mist-shrouded slope into the train, bouncing up to break through windows or battering against the carriage sides. One vast boulder headed straight towards me; I ran down the corridor. The air was full of crashes and thuds and the sound of distant, confused, undirected gunfire. I felt the train shake, then a tremendous bang obliterated every other noise; the lava vaporising the lake, the gunfire, the small rocks whacking onto the sides and roof. The entire carriage flicked to one side, dashing me against the window and then over on my back as the car lights flickered and went out, a breaking, smashing sound seemed to come from all directions at once, and the buckling carriage roof and walls batted me between them like a ball.

Later, I discovered that the carriage had broken free from the rest of the stricken train and rolled down the slope of scree towards the boiling waters of the lake. The Field Marshal's men, looting and murdering their way through the cars, came upon me, mumbling to myself in the wreckage and - so they tell me, though they'd say anything-attempting to put the chief steward's head back onto what was left of his shoulders. I had stuck an apple in his mouth.

Language saved me again. The men speak the same tongue as I do; they took me to the Field Marshal. He was in a small train just up the line.

The Field Marshal is very tall and heavy, with long, disproportionate legs and a huge backside. He has a broad, round face and lank hair, dyed black. He favours garish uniforms with a very high albedo. He was sitting at a desk in his carriage, listening to music on the radio and eating crystallised quinces from a small plate when I was ushered before him, still half unconscious. He asked me where I came from; I vaguely recall telling him the truth, which he found extremely funny. You'll be my valet, he told me. I like a good story at dinner. I was locked in a small cell in one of the carriages while the Field Marshal's men completed their looting and killing. When I was searched, my handkerchief was taken from me. I saw the Field Marshal blowing his nose on it, some days later.

I watched the blood-splashed irregulars of the Field Marshal's force come back from my old train, carrying weapons and valuables; a wind came up and stirred the steam in the valley's cauldron. The lake was almost dry; lava flow and glacier finally met in a series of tremendous explosions which sent chunks of ice and rock hundreds of feet into the air. Our small train escaped, clanking and clattering, away from the wreck on the track behind us, and the elemental cataclysm beyond.