'I see,' said Ballista.
'Is it good?'
'Very good.'
'The fuse leads two-thirds of the way out of the tunnel. When you are clear, call to me and, with your permission, I will light it.'
'You have my permission.'
'Then let's go.'
Back on the surface the sunlight was blinding. Tears ran from their eyes. Having got his breath back, Ballista called to Castricius to fire the mine. They stepped away from the entrance.
For some time nothing happened. Then they heard the sound of Castricius's boots dislodging stones as he ran. He shot out of the tunnel, bent double but running hard. He skidded to a halt, looked around and, blinking hard, walked over to the others.
'It is done. Now it is in the hands of the gods.'
They struggled back into their armour and sword belts and ran to the tower. Taking the steps two at a time, Ballista burst out on to the battlements. He dived behind the parapet and looked out.
Almost everything was as it had been before. Yet Ballista knew something was wrong. There was the void. There was the Persian ramp with the screens along its face. Further back, level with the base of the ramp, was the line of mantlets. Further back still were the Persian artillery emplacements. Ballista searched hard, but he could see no wisp of smoke escape from the ramp. There was no evidence of what should be happening. There was no sign of the conflagration that should be raging in the manmade cavern below, the terrible fire that should be burning through the props, bringing down the cavern roof and the whole ramp above it. Everything on the surface was completely still.
That was it: everything was completely still – no incoming artillery, no archery, no rubble being tipped into the void. It would be now: the assault would come any second now.
'Haddudad, get the men up on the wall. The reptiles are coming.' Even as he shouted to the mercenary captain, Ballista saw the screen at the front of the Persian ramp begin to tip up. Allfather, we are going to lose this race. So close – just a few minutes more was all we needed.
The screen was pulled horizontal. Ballista ducked back behind the crenellations. A volley of arrows like a swarm of hornets buzzed across the fighting top, snickering off the stone. A sentry howled. The arrow in his shoulder, he spun round, lost his footing and tumbled down the slope of the inner earth ramp, where he got in the way of some legionaries coming out of their dug-outs and beginning the climb.
The arrow storm stopped. Ballista quickly glanced out. The boarding bridge was being pushed towards him across the void. A vicious-looking spike stuck down from beneath its leading edge. Ballista looked back inside the town. The defenders were labouring up the inner glacis, Roman regulars, mercenaries and local levies combined: they would not make it in time.
The boarding bridge crashed down, its spike well over the parapet. Without thinking, Ballista grabbed it. The wood was warm and smooth under his right hand. He swung his legs up on to the bridge. His boots thumped hollowly as he landed. Side on, shield well out in front, he drew his sword. He heard Maximus's boots thump down just to his left, those of another defender beyond the Hibernian. The boarding bridge was not wide. If no one fell, three men might hold it – at least for a short time.
In front was a line of fierce, dark, bearded faces, mouths open, yelling hatred. Under a coating of dust were the bright colours of Sassanid surcoats and the shine of their armour. Their boots drummed on the boarding bridge.
The easterner hurled himself baying at Ballista, not even trying to use the long sword in his hand. He wanted to smash his shield into that of the northerner, simply drive the defender back and off the bridge.
Ballista let himself begin to be pushed backwards. He stepped away to the right with his rear foot – there was no railing to the bridge; his boot was far too near the edge – and brought his left foot back behind his right. The Persian's momentum drew him on. As Ballista's body turned, he brought his sword over and, palm down, he stabbed it into the easterner's collarbone. There was a momentary resistance from the mail coat, then the point slid in, cutting through the soft flesh, scraping down the bone.
As the first Sassanid fell, beside and behind Ballista, the next came on. Ballista dropped to one knee and swung the sword in a wide arc at the man's ankle. The Persian hastily dropped his shield to take the blow. Leaning over, off balance, the man had little chance. Ballista lunged forward and up, driving his shield into the man's chest, knocking him back and sideways. There was a momentary look of horror on the Persian's face as he realized that there was nothing under his boots, that he had been driven over the edge of the bridge; then he fell backwards, arms waving into the void.
For a second Ballista teetered on the edge, then he regained his balance. He glanced to his left. There were two Persians on the floor around Maximus. Beyond that, one of the equites singulares was down, but another had taken his place. Calling to the other two defenders to stay with him, Ballista carefully stepped back over the body of the first Sassanid he had killed.
The line of angry, contorted faces stopped. To get at the defenders they would have to risk the uneven footing of stepping on or over the bodies of four dead or dying men. The Sassanids were no cowards, but it would be a fool who would willingly put himself at a disadvantage in a fight like this.
Ballista felt a surge of confidence: he could do this; he was good at this. A perfect Thessalian feint followed by taking the man over the edge. The northerner's euphoria was broken by a vicious pain in his right thigh. There was a thin white line, which suddenly swelled into a red gash. As the blood ran down he shifted his leg. It hurt. It hurt a lot. But it would take his weight. The arrow had caused only a glancing flesh wound.
Crouching low behind his shield, arrows flying in from both sides, Ballista looked over the edge at the siege ramp. He thought he saw a wisp of smoke curling out of the mud bricks at the side of the ramp. It was gone before he could be certain. Sweat ran down his back. Maddeningly, a fly tried again and again to land on his eyes. His leg was throbbing; soon it would stiffen up.
A Sassanid nobleman was shouting at the storming party on the ramp. Any moment now they would recover their nerve. Ballista looked over the edge again.
There! There was a wisp of smoke. This time he was sure. Another, and another.
The Sassanids on the boarding bridge knew that something was wrong. They stopped yelling, stopped screaming at the defenders. They looked from one to another, puzzled. It was the noise, something beyond the sounds of men in combat, something deep, low and elemental, something like a wave crashing on a rocky shore.
As Ballista watched, smoke leaked out from all over the siege ramp. The noise changed to the deep rumble of an earthquake. The ramp seemed to quiver. The boarding bridge began to buck wildly. The looks on the Sassanid faces changed to terror. Slowly at first, then too sudden to follow, the centre of the ramp sank out of sight. The three side walls held for a moment. The boarding bridge swayed above the abyss.
'Jump!'
As he shouted, Ballista spun round and started to run. The. wooden boards under his feet tipped up. He was scrabbling upwards on his hands and knees, his sword swinging dangerously from its wrist loop. The boarding bridge slid backwards down into the void. Its spike snagged for a moment on the parapet.
With a leap born of desperation, the leap of a salmon, Ballista just got the fingers of his right hand over the end of the bridge. There was a deafening roar. A mushroom cloud of choking dust and smoke blinded him. The parapet gave way. The boarding bridge began to slide down into the abyss.