The warriors facing us were being grown in vats, or something worse, I felt sure of it. I suspected they fought so hard because they knew they were going to die anyway. They all seemed riddled with disease.

Even as I watched, the stomach of one – bloated hugely with corpse gas – exploded, sending a cloud of blood and entrails and something else into the air. The mortal remains spattered to the ground around it, but the extra stuff seemed to float in the air, like spores adrift on the wind.

‘That was quite a fart,’ said Anton, trying to make a dumb joke of it as always, but Ivan was ahead of him.

‘What new hellishness is this?’ he asked. More and more of the corpses were exploding, entrails bursting out, clouds of spores hovering over them. I glanced around and shouted, ‘Everybody make sure your rebreathers are tight.’

The men were Lion Guard. They should not have had to be told, but I like to be certain. I walked along the line making sure all of their masks were well adjusted and then I returned to the post where Anton and Ivan were waiting. I raised the magnoculars and checked again, for something had struck me.

I was right. The corpses that were exploding all seemed to have the same face, and it was one I had not seen before in previous attacks. I thought about what the medic had said, about new diseases being cross-bred. Maybe this new type of soldier was a new type of weapon bearing a new type of plague.

Even as the thought was running through my mind, a shot rang out. I looked at Anton who had raised the sniper rifle to his shoulder and fired. ‘One of them was moving,’ he said. ‘One of the heretics. He must not have been quite dead.’

Lasguns fired along the line now, bolts cutting through the gloom. I wondered whether Anton’s shot had triggered a nervous reaction and the men were simply spooked, but a corpse rose from the heap on the hillside and tottered forward a few feet, blood dripping from its eyes like tears. It got caught in the barbed wire and tried to continue, its flesh being raked off by the spikes. Anton’s shot exploded its head and it fell.

More and more of the corpses had started to move, pulling themselves up.

‘Must have been playing dead,’ muttered Anton, but I knew he was wrong. Several of the bodies were trailing their own entrails. One of them had a hole in his chest cavity that showed where his heart had been burned out.

‘Steady, lads,’ I shouted. The Lion Guard kept firing. The ambulatory corpses were put down again.

Ivan said, ‘Tell them to stop shooting.’

I was going to ask why but instead I bellowed the order. I watched and I saw what Ivan had noticed. Each of the corpses staggered forward only a few metres and then collapsed again, and did not rise.

‘Must be some new disease,’ Ivan said. ‘Makes them run around like headless chickens, even after they are dead.’

I kept my eyes on them nonetheless. I was unnerved by this latest development. Corpses moving by some sort of delayed reflex action I could believe, but not hours after they had been shot. Men waking up wounded on a battlefield was a possibility, but not in such numbers and not with such wounds.