Hidden in the unlit colonnade, Ballista waited. It was the last hours of the night, some time after the start of the fourth watch. Away from the palace to the south, across the open space of the citadel, he could make out furtive figures in the darkened temple of the Tyche of Zeugma. Without Ballista consciously directing it, his right hand moved: first to the dagger on his right hip, freeing it an inch or so from its sheath and snapping it back, then to the sword hanging on his left, drawing it a couple of inches and pushing it home again, finally to the healing stone tied to the scabbard. What was going to happen was all bad. But he had no choice but to play his part.

At last he heard them moving up the hill; a confused murmur of voices, the rattle of weapons, no attempt at concealment. As the first of them came through the gate, the torches they carried flickered through the leaves of the fruit trees. Snatches of boisterous, rough voices reached Ballista. The men emerged from the orchard fully armed for war – helmets, mail shirts, shields and weapons. But the column was in no order. The soldiers walked with friends from their units, talking in loose groups. The centurions present led some of them off to left and right. In no time at all, the palace was surrounded.

There goes all hope of escape, thought Ballista. His mind had been running on slipping away on the far side of the citadel; down through the trees, over the low wall, across the roofs, saddling Pale Horse and riding west, following the route Castricius’s man had shown Calgacus and the others. Of course it had been an idle thought. Even if he reached Antioch, how would he get Julia and the boys away? Come to that, what welcome would Gallienus give him in the west? He remembered entertaining a similar idea before the siege of Arete. Childish fantasies. It was time he put such things aside. Still, it was good of Castricius to have reunited him with Pale Horse and his own weapons. He touched the healing stone again.

The ring of armed men around the palace began to chant.

‘Come out! Show yourselves! Quietus and Macrianus, come out! You cannot hide from the soldiers!’

Nothing happened. The soldiers clashed their weapons on their shields. Their chants became impatient. Flasks of drink passed from hand to hand. One or two whistled, called out obscenities.

This cannot go on for long, thought Ballista.

A rectangle of orange light sprang out from the palace as a door opened.

‘Come out! Come out!’

Quietus and Macrianus the Younger stepped out. There was tension in their movements, none of the usual arrogant swagger.

Macrianus the Younger raised his right arm in an oratorical pose. The noise from the soldiers gradually fell away. Torches hissed in the night air.

‘Soldiers of Rome, what is the meaning of this? Have you forgotten your disciplina? Return to your quarters.’

‘Never! Never!’ The men roared back.

Now Quietus came forward. His arms were stretched out in entreaty. ‘Remember our youth, our blameless lives. Have pity on our father’s grey hairs. Do not put us in this danger. We have not asked for this. We have done nothing to deserve it.’

A few soldiers laughed. Then, as if at an order, they all began a rhythmic chant:

‘Quietus imperator, Augustus free from all guilt, may the gods keep you. Macrianus imperator, Augustus free from all guilt, may the gods keep you.’

Over and over, the words were chanted. Quietus and Macrianus the Younger made half-hearted gestures of unwillingness.

From the gloom, Ballista listened and watched. He had heard that, in some Scythian tribes, a man’s ritual reluctance to rule was overcome by pelting him with mud. It seemed a custom the Romans could adopt with profit.

A new chant boomed out. ‘The good faith of the soldiers, happiness!’ Louder and louder it was repeated. ‘Fidei militum feliciter! Fidei militum feliciter!’

Slowly, Macrianus the Lame made his way out of the palace to stand between his sons. He raised his walking stick. The silver head of Alexander glinted. The soldiers instantly stopped chanting. The father gestured Quietus to speak.

‘Fellow soldiers, it is a heavy burden you wish to place on our shoulders. Commilitiones, you know that neither my brother nor myself has sought this honour. Yet the gods know our love for the Res Publica.’

Quietus paused, as if in deep thought – the effect slightly spoilt by the half-smile on his weak mouth.

‘Commilitiones, we hear your command. The soldiers of Rome are the sword and shield of the imperium, the embodiment of our ancient virtus. But to be Augustus is not just to be a military commander. Our minds would be easier, our burden less heavy, if we knew that the senate and people also called us to the purple.’

As Quietus finished, lights blazed out from the temple behind the soldiers. Through its open doors Ballista could see a group of civilians gathered around the statue of the Tyche of Zeugma. The ring of soldiers opened to let them pass.

Maeonius Astyanax, toga-clad and backed by other senators, halted before the candidates for the throne. In the torchlight, his eyes were like pebbles under water.

‘Too long the ship of state has drifted, no firm hand on the rudder. Valerian was old and ineffectual. Now he is gone, may the gods have mercy on him. His son, Gallienus, lies sunk in luxury and debauchery. Shunning the senate house, the forum and the army camp, he disports himself with pimps and prostitutes, actors and barbarians. Fit only to be dragged with a hook, he brings disgrace and disaster. The throne of the Caesars calls for vigorous young men of courage and decency. The senate calls for Titus Fulvius Iunius Quietus and Titus Fulvius Iunius Macrianus. Take the purple. Each of you: trust us, trust yourself!’

The senators took up the call: ‘Crede nobis, crede tibi; crede nobis, crede tibi.’

At the twenty-fifth repetition, another group of civilians came forth from the temple. The man at their head looked overawed. He was sweating heavily.

‘I am Barlaha, son of Antiochus, a member of the Boule of this city.’

Some of the soldiers, well refreshed with wine, sniggered. Barlaha stumbled on.

‘Rome has made one city of the civilized world. She has given all who dwell in the imperium citizenship. All the citizens of Rome speak through us, the Boule of Zeugma, when we call Quietus and Macrianus to the throne.’

The two young men inclined their heads in acceptance.

‘The immortal gods grant long life to Augustus Quietus, long life to Augustus Macrianus. Happy are we in your imperium, happy the Res Publica.’

Like a well-trained chorus, the audience chanted.

Two small groups of soldiers encircled Quietus and Macrianus. A flat, oval infantry shield was placed on the ground before each brother. They stood on them. The soldiers bent down and carefully, if with a certain unsteadiness, lifted the shields and raised Quietus and Macrianus to the heavens.

Macrianus the Younger, wobbling just a little, waved and made a fair show of imperial dignitas. Quietus, pouchy little eyes darting here and there, could contain himself no longer. Now and then clutching at the top of a soldier’s head for balance, he giggled in open exultation.

Once the two young men were safely back on terra firma, their father embraced them and spoke.

‘This has been so sudden, so unexpected, the hands of the gods must be behind it. Man must always bow to the dictates of the divine. But it has been so sudden that the necessary regalia is not prepared.’ The old man produced two ropes of gold, glittering with jewels. ‘These were your late mother’s necklaces; for now, use them as diadems.’

Quietus held up his hand. ‘Thank you, Father, but no; such a female adornment would not be right. There will be nothing womanly about our reign,’ he simpered.

A couple of cavalrymen approached. ‘Use these gilded horse trappings, Domini.’

This time it was Macrianus the Younger who demurred. ‘Many thanks, commilitiones, but what has been worn by a beast would impair the dignitas of an Augustus.’

There was an awkward pause. A centurion hissed, ‘Now, you fools.’ Two standard bearers shuffled up. They removed the gold collars from their necks. Evidently overcome by the occasion – or by alcohol – they had forgotten their lines. The new emperors snatched the offerings and placed them on their own heads.

Servants swarmed out. Two purple cloaks were produced and draped around the shoulders of Quietus and Macrianus. In front of each was placed a low altar on which burned the sacred fire of an emperor. Behind them, men ran about fixing imperial symbols to the front of the palace: eagles, the shield of four virtues, wreaths, bay leaves for victory, oak leaves for saving citizens’ lives.

All of this rather gave the lie to the ‘impromptu’ nature of the events, thought Ballista. He would not be able to remain lurking in anonymity behind a column for long. His own unwanted part in these ghastly theatrics was fast approaching. He fiddled with his sword.

It was Quietus who made the expected formal speech of acceptance.

‘Commilitiones, senators, citizens of Rome, it is with humility that we accede to your demand and take the imperium. Our joint reign will be marked by courage, clemency, justice and piety.’ He gestured at the golden shield now being hammered to the wall behind him on which ‘Virtus’, ‘Clementia’, ‘Iustitia’ and ‘Pietas’ were inscribed.

‘It is gratifying to us that the senate, people and soldiers unanimously call us to the throne,’ continued Quietus. ‘All shall benefit. The senate shall return to its ancient dignitas. Our consilium shall be open to senators. The senate house will be purged of informers. Senators will be free of unjust condemnations and confiscations of their estates. The great military commands will again be open to men of the senatorial order.’

The senators at least cheered this with enthusiasm.

‘To the people, their ancient libertas will return. We decree that ten days of games will be held, starting as soon as gladiators and animals can be gathered.’

The town councillors of Zeugma, as the only representatives of the people on hand, made suitably grateful noises.

‘Fitting reward must be given to the loyalty of the soldiers – two gold pieces to every man with the standards. But to those of our commilitiones present, to those through whom the gods brought us to the throne, much more is due.’

Quietus had his audience now.

‘The majority of the Praetorian Guard was lost with Valerian. All those here will be enrolled in the reformed unit, and accrue the resulting increases in pay.’

The men cheered. Shouts of ‘Rich soldier’ broke out. Quietus gestured for silence. He was ignored until his father joined in.

‘And a donative – five gold pieces and a pound of silver per man,’ Quietus continued.

The shouts returned, much louder, swelling into unison: ‘Dives miles! Dives miles!’

Again Macrianus the Lame had to calm the throng.

Quietus resumed. ‘A new guard needs a new commander. A man of loyalty. As our new Praetorian Prefect, it is right that Maeonius Astyanax should be first to take the sacramentum in our reign.’

Chin high, short beard jutting, Astyanax stepped up and took the military oath:

‘By Jupiter Optimus Maximus and all the gods, I swear to carry out the emperors’ commands, never desert the standards or shirk death, to value the safety of the emperors above everything.’

Ballista listened to the words with misery. He had broken the sacramentum he had made to Maximinus Thrax and earned himself the undying hatred of that emperor’s daemon. He had broken his oath to Valerian. Now he was about to take another sacramentum, one he had no intention of keeping. But all this was nothing. It was breaking the oath to Shapur that plagued him: Spill my brains on the ground … my brains and the brains of my sons too.

Next up was Gaius Calpurnius Piso Frugi, the new governor of Syria Coele. He was followed by the other two governors present, Annius Cornicula of Syria Phoenice and Achaeus of Palestine. Then it was the turn of Ballista, the Vir Perfectissimus, Prefect of Cavalry, as he was announced.

As Ballista stepped out, most of the soldiers cheered perfunctorily, but one group showed real enthusiasm. The eagle, lion and Capricorn on their shields showed them to be from Legio IIII Scythica. They must have been part of the detachment that fought under Ballista at Circesium. The distinctive angular face and huge hooked nose of one of the legionaries confirmed it – Ahala, Aharna, his name was something like that. His was not a face you would easily forget. Ballista waved.

Having mouthed the words of the oath in a daze, Ballista found himself part of the new emperors’ entourage. He watched as everyone else took the sacramentum; those of importance as individuals, others in groups. The ceremony was far from over. When the oath-taking was done, they would process down to the main army camp and tour selected temples in the town before climbing the hill again for dedications in the temple of the Tyche of Zeugma and an audience in the palace.

Ballista supposed the ceremony had been well enough planned. Certainly Astyanax had devoted much effort to it; even trawling through old acts of the senate to select exactly right ‘spontaneous’ acclamations. Holding it at night had added some drama. Allowing only those soldiers already selected for the Praetorian Guards had been sensible. The unexpectedly generous donative had generated genuine excitement. Ballista could see the point of the theatricals with the diadems. It was meant to show that the new emperors had the dignitas of the imperium at heart, were close to their soldiers and could stand up to their father. Of course it was all nonsense.

Although the ceremony was passing off well, the same could not be said for the realities of the bid for power. Admittedly, all Roman provinces east of the Aegean had come over, including the initially uncertain military ones of Egypt, Arabia, Osrhoene and Syria Phoenice. But no governor in the west had declared for the sons of Macrianus, despite the sending of urgent letters accompanied by large bribes. And there was no possibility of winning over the vital Danubian armies now Ingenuus was leading his own revolt.

Far worse than all this, the Persians were on the move. Bypassing Edessa, they had crossed the Euphrates and taken Samosata. Macrianus the Lame had adopted what he called a strategy of containment. In the face of the Persian advance, Samosata had been hurriedly abandoned. The twenty thousand Roman troops there had been divided. Ten thousand had rushed south to Zeugma with the emperors-to-be. Five thousand had been sent north to reinforce the governor of Cappadocia, Pomponius Bassus. The final five thousand had been ordered to Doliche to block the road west. Ballista saw the latter as the problem. Unsupported, they had no chance of preventing Shapur riding west to Cilicia and beyond, should he wish.

Of course, there was another problem looming in the east. The Lion of the Sun. Still no word had come back from Odenathus. No one knew what the Lord of Palmyra would do. Would he join the revolt? Would he remain loyal to Gallienus? Was it possible he would throw in his lot with the Persians? Only a couple of months before, Ballista had been there when Odenathus had sent envoys to Shapur. They had been rejected, but events had moved fast, and a second approach might yield a very different outcome.

And then there were the gods. Macrianus the Lame had consulted widely among the oracles of the east. The responses were far from uniformly favourable. At the shrine of Aphrodite Aphacitis in the mountains between Byblos and Heliopolis was a sacred lake. If the offerings thrown in were accepted by the goddess, they sank, light and heavy alike. If rejected, they did not. The gifts of Macrianus – silk and linen, gold and silver – all had floated. The oracle of Apollo Sarpedon at Seleuceia in Cilicia had been similarly robust. When the envoys of Macrianus had asked about the success of the uprising, the god gave a reply that no amount of sophistry could make favourable:

Since breaking his oath to Shapur, the gods were much on Ballista’s mind. Were all the gods the same? If not, could his northern gods protect his sons from the southern gods of the Greeks and Romans? And even were they able to, would they wish to? Somehow, he doubted it. But he prayed anyway: Allfather, Hooded One, Death-blinder …

*

The bad news had reached Zeugma six days before. The Persians had marched from Samosata. With no warning, they had appeared before the walls of Doliche to the north-west of Zeugma. Outnumbered, the Roman force of five thousand stationed there could do nothing but watch them sweep on to the west. The following day, an exhausted scout had ridden into Zeugma with the further news that the enemy were taking the road up into the Amanus mountains, heading for the Amanikai Gates. Once through that undefended mountain pass, Shapur’s force, variously estimated at fifteen, thirty and fifty thousand men, would have the rich territory of Cilicia Pedias and the unarmed provinces of Asia Minor at its mercy.

Having predicted just these events won Ballista no commendation. Summoned before the new emperors, the northerner was brusquely ordered to take five thousand cavalry, ride west and defend Antioch. The Syrian Gates, the southern pass back over the Amanus range, must be held at all cost. Similarly, Seleuceia in Pieria, the port of Antioch, had to be defended in case the Persians commandeered ships along the Cilician coast.

It had taken Ballista some effort and considerable patience to explain to the unmilitary father of the young emperors that, to hold ground, one needed infantry. Eventually he had been given permission to replace one thousand of the cavalry with mounted infantry. He was to requisition a thousand horses and mount on them any legionaries he could find from Legio IIII Scythica who admitted any hint of equine experience. His old companion Castricius was to accompany him.

The journey had been hard. It was July, blazingly hot in Syria, so they had left at dusk. They had reined in after a couple of miles to check girths and tack. Then they had ridden on until nearly noon the next day. Some sixteen hours in the saddle, with just a brief halt every hour to drink and four longer ones to give their mounts some respite from the weight on their backs. They were eating up the ground, but it was tough on man and beast.

Three days of this and they had reached the village of Gindaros. From there, still keeping to this regime, Castricius had taken half the force on towards Antioch and Seleuceia. Ballista had rested his men overnight in the village. He would need daylight for the last stretch of his march, crossing the swampy and roadless plain to the north of the Lake of Antioch.

Now, finally, they were in an unprepossessing village called Pagrae at the foot of the Amanus range. Their blistering pace had had an effect. Of the two thousand cavalry, half bowmen, half spear-armed, some two hundred had dropped out. Unsurprisingly, things were much worse with the mounted legionaries. Only about three hundred of the complement of five hundred remained. Ballista wondered how many men Castricius would still have with him when he reached the coast. The centurion had faced another two days’ travel when he rode out of Gindaros. Still, Ballista had instructed him to gather any troops he could find in Antioch.

It was early evening. The men were looking to their horses, settling in. They would spend at least some of the night here, gathering their strength. They would need it, but there would be no such luxury for Ballista.

The village headman had provided information. It was about five miles to the narrows of the Syrian Gates, the road good but demanding. He had also recommended a guide; a wiry goatherd. Having asked for volunteers, Ballista had selected two scouts from the cavalry. On his instructions, the exploratores had discarded all armour and weapons except their sword belts, tied scarves around their heads and put on dark cloaks. They had bound their horses’ hooves to muffle the noise of their approach. Reluctantly swapping Pale Horse for a black gelding, Ballista had done the same.

Having eaten, relieved himself and handed over command to one of the prefects of cavalry, a Syrian with the impeccably Roman name of Servius, Ballista could see no reason to delay. He gave the order. They rode out of the village and took the road up into the mountains.

It was a dark night. The wind from the east was pushing black clouds across the stars. Possibly it would rain later, one of those sudden torrential summer thunderstorms. Initially the incline was gentle, the hills wide-spaced, but soon the slopes reared up and came close. Beside Ballista, the goatherd on his pony did not talk. The exploratores behind were quiet also. An owl hooted, and another replied. Once, something sent a scatter of stones rattling down the slope to their right. Apart from that, there was just the creak of leather and the deadened sound of the horses’ footfall.

When the ascent became steep, Ballista spelled the horses, the men swinging down to walk for a time before getting back up. With the repetitive landscape and their fatigue, time soon lost meaning. There was nothing but the road and scrub-covered rocks all around.

Possibly, this would all go well. Ballista would find the defile of the Syrian Gates empty. They could wait peacefully in the pass while one of the exploratores galloped back to tell Servius to rouse out the men and bring them up.

Ballista regretted not writing a note for Castricius to give to Julia as he passed through Antioch. But it would have delayed the centurion, and he did not dare to entrust it to anyone else. The imperial spies were never more active than at a time of insurrection. Censorinus, the feared head of the frumentarii, had long been close to Macrianus the Lame. He would have his men prying into everything. Beyond a formal note saying that he was safe, Ballista had not written to Julia since his return, since the breaking of his oath.

The goatherd’s outstretched arm startled Ballista. Unnecessarily indicating silence, the man mimed that they should dismount. Having handed his reins to one of the exploratores, Ballista took stock. The mountain walls had come closer on either side. The road ran up straight for another hundred or so paces then turned to the right. The goatherd put his mouth to Ballista’s ear. He smelled rank, like one of his animals. The Syrian Gates were ahead, around the bend.

Alone and on foot, Ballista set off. There was no cover beyond a few fallen rocks at the sides of the path. He walked on the balls of his feet, feeling for loose stones before he put his weight down. He stayed close to the right mountain wall. Moving inconspicuously at night was not a problem for him. Following the custom of his people, as a youth he had gone to learn warcraft in the tribe of his maternal uncle. He had been lucky his mother came from the Harii. They were feared night-fighters.

When he reached the turning, Ballista remained motionless for a time, stilling his breathing, listening hard. Nothing. He sniffed the air. Nothing. He listened some more. When there was still nothing, he crouched down, carefully arranging his belt over his back so that his scabbard lay between his shoulderblades, the hilt of his sword just behind his head. Looking back the way he had come, he half noticed the dark shape of his companions. That was of no interest. When the shadow of one of the clouds came in from the east, he looked round the corner.

The low, smouldering fire was unexpected: bright red in the night. Ballista did not look directly at it. Keeping his eyes on his hands and feet, he crawled to a fallen rock and lay behind it.

Closing one eye to keep his night vision, Ballista studied the scene. The road ran about one hundred and fifty paces to the fire. It grew increasingly narrow. The rock walls were jagged; at the fire, no more than fifty paces apart.

There was a campfire burning in the Syrian Gates. The wind was from the east. That was why Ballista had not smelled it. He could see the silhouette of what looked like a small cart. Other smaller, dark shapes indicated men by the fire. A group was spending the night there. But who were they? It could be an innocent caravan. But it could be a Sassanid war party.

For a long time, Ballista lay silent, hoping to hear what language the men by the fire spoke. Now and then, he heard a murmur of conversation, but they were talking low, and the wind was against him. There was nothing for it: he would have to get closer.

Waiting for the clouds, using the movement of their shadows, Ballista crawled nearer. It was slow, painful going. His hands were cut, knees grazed. The last twenty-five to thirty paces, there was no cover. Ballista stretched out behind a rock little bigger than his head. The cloud cover had increased, but every time it cleared he felt horribly exposed. Suddenly, from beyond the camp, a horse called. From behind him, clear on the freshening breeze, came an answering neigh from one of the Roman horses.

There were voices from the fire now: ‘Did you hear that?’ ‘What?’ ‘Listen!’ They were Persians.

Outlined by the glow, two men stood up.

‘We should go and look.’

‘Not me. Who knows what daemons lurk in these hills at night?’

A third man spoke. His voice conveyed authority: he must be some form of officer. ‘If it was not misfortune enough to be sat on this bleak mountain missing all the pleasure the others are enjoying in Iskanderun – but to be stuck with a man who sees a Roman behind every rock, and another who fears devs everywhere. Sit down. Let the night pass quietly.’

The men sat.

If he had not been so well trained, Ballista would have sighed with relief.

It was mid-morning the following day when Ballista returned to the Syrian Gates. Time plays tricks. His crawl back to the others had seemed to take for ever; the ride to Pagrae passed in moments. He had given orders and fallen into a heavy sleep for a couple of hours.

The troops had been roused well before dawn. Having been tormented by mosquitoes, few complained.

Ballista had called a consilium of officers, down to the rank of optio. He had made sure everyone knew the order of march and his tactical plan, such as it was. They were to explain it to the men under them and see that all had a good breakfast.

Food was important. Ballista knew the Persians ate only a light breakfast but took lunch earlier than westerners. If his timing was right, his men would be well fed, the Sassanids hungry. It was not much of an advantage to build on. This was a battle that would be decided by the disciplina and sheer fighting quality of the Romans; above all, that of the legionaries.

The march up had been glorious. In daylight, the Amanus range had revealed its beauty. The men had climbed upwards in the shadow of pine and wild olives, between banks of lavender and myrtle. In every shelf of soil, every crevice where a tree could thrust its roots, was a mass of vegetation. The view, looking backwards, at times took in the whole plain, with the lake of Antioch glittering in the centre and the valley of the Orontes off to the south.

They had marched on foot, quickly, but with no attempt at concealment. There was no chance of surprising the Sassanids. A column of over two thousand armed men cannot but make a lot of noise, but their numbers would only be sufficient if the Persians had not had time to summon reinforcements.

As they halted near the summit, the wind picked up. Big, dark stormclouds again rolled in from the east. Strong gusts tugged at Ballista as he made a final check that everything was in order.

At the front were the saddlesore, aching legionaries; a block fifty wide and six deep, close-packed. Behind them were five hundred dismounted horse archers, in loose order. The rest, nine hundred spear-armed and four hundred bowmen, again all on foot, were stationed as a reserve a few hundred paces back, where the space was wider.

‘Remember, boys, they are just a bunch of easterners. They hate fighting on foot, and they get frightened close to the steel.’ Ballista had to bellow to compete with the wind. Even so, he was not sure how many even of the legionaries could hear him. ‘Get through the arrows and we will kill them. Remember they carry their wealth on their persons. But no looting until the order. Keep your places. Look after your brothers.’

The legionaries clashed swords on shields.

‘Are you ready for war?’

‘Ready!’

When the third response echoed from the rocks, Ballista took his place in the front rank. His right hand freed his dagger a little then snapped it back, drew his sword an inch or two then rammed it back, and finally touched the healing stone on the scabbard. His personal pre-battle drill done, he took up the borrowed oval shield, and told the bucinatores to sound the advance.

As they trudged the last fifty paces to the turning, Ballista wondered how this would turn out. He had no idea how many Persians they were facing. The vital snatch of conversation he had overheard the night before suggested that the majority of the enemy force was down in the western plain, sacking Iskanderun, as the Persians seemed to call the town of Alexandria ad Issum. But, as he did not know how many easterners there were in total, it meant next to nothing. Again, he did not know what, if any, obstructions or defences they might have placed in the defile. All he had seen was a fire, a handful of men and a cart. It would all fall out as the gods willed it. One thing was certain. It would be unwise for a man who had broken an oath to the Persian king to let himself be taken prisoner. Ballista thought of the cell in Carrhae, thought of what had nearly happened there. No, he was not going to be taken alive.

The men of Legio IIII Scythica jogged round the corner and into range of the eastern bows. They heard yelled Persian orders. The sky darkened.

‘Testudo!’ Ballista’s was not the only voice shouting. He crouched and held his shield out in front of him. The man behind slammed his shield down on the top edge of Ballista’s, covering the northerner’s head. The noise was repeated from behind as the shields of each rank in turn slammed home, overlapping like tiles on a roof.

Seconds later came the arrows, thumping into wood, dinging off metal bosses, skittering off the road. Ballista felt the shield above him bang down on to his helmet as an arrow struck. Somewhere, a man screamed. Nearby, a man swore fluently. Another was praying.

‘Bind and advance.’

Ballista grabbed the back of the mail shirt of the man to his right, gripped it in his fist. He felt his own tighten as the man to his left did the same. Half turned to the right, taking short steps, crabwise, the left foot always first, they advanced.

‘Left, left, left,’ they muttered, getting into rhythm, the momentum mounting.

Another volley of arrows whistled down. More men screamed, cursed. More men were praying, calling out encouragement.

‘Only officers will speak! This is not a fucking symposium!’

It was hot and close in the testudo; a strong smell of sweat and unwashed men. Ballista peeked out of the gap between the top of his shield and the overlapping one to the right. The air was full of missiles. A line of men. Incongruous in the centre, a four-wheeled cart. A long way to go. At least a hundred paces.

The arrows fell like rain. The Persians were shooting at will.

A cheer spread through the testudo. The Roman bowmen were round the corner. They were shooting back. Now the Sassanids could try the bitter luck of war.

Above all the noise – the impact of arrows, the hard breathing, the rattle of equipment, the intermittent howls of pain – there was a rumble of thunder.

Ballista risked another look around his shield. Getting there: about sixty paces to go. But something struck him as odd. There were fewer missiles in the air. A commotion in the centre of the Sassanid line. Warriors pushing the cart forward.

‘Halt!’

Surprised, but obedient to orders, the legionaries bumped into each other as they came to a sudden stop.

The easterners had let go of the cart. It was beginning to gather speed down the incline.

‘Legio IIII, lie down. Cover yourselves with your shields. Pass the word back to the archers to stay on their feet and spread out.’

In a confused, uncertain scramble, the men around Ballista got to the ground.

‘Face down. Shields over your backs.’

Ballista had no time to explain or check that his instructions were carried out. The cart was moving faster. He dropped down, nose an inch or so from the road, grit under his elbows, shield braced above his head.

The terrible rumbling and squealing grew louder as cart and the inevitable collision drew near. The trick had worked for Alexander the Great. Arrian’s Anabasis, Ballista thought. That was where he had read about it.

There was an awful sound of splintering wood, agonized screams. A moment’s silence, then a sickening crash.

‘On your feet. Close ranks.’

Alexander’s ploy had not worked so well for Ballista. At the front, men were down where the wheels had hit them. The cart must have been airborne for a time. But it had not cleared the unit. There was a mangled mess of broken bodies and shattered woodwork where it had landed, towards the rear. The sound of low sobbing could be heard.

‘On your feet! Close ranks.’ The legionaries, eyes wild with shock, were slow to move. ‘Close ranks!’ Ballista took stock as the men shuffled to obey. The incoming arrows had dropped away as the Persians watched. Still about sixty paces to go: further than he would have liked. But the legionaries were in no state to reform the testudo. It had to be now.

‘Ready for war?’ Ballista roared at the darkening sky.

‘Ready!’ Each time, the routine response was bolder, more angry. After the third, Ballista ordered the charge.

As they set off, swords drawn, the arrow storm recommenced.

The road was steep here. Within a few paces, Ballista felt the muscles in his legs complain. His chest began to burn as he dragged in air. Another peal of thunder.

Splinters flew hideously close to Ballista’s eyes. He felt a sharp stab of pain, blood hot on his cheek. The wicked barbed point was near his face. An arrow had punched half through his shield. He snapped the shaft. Kept moving.

The Sassanid now facing Ballista was coming forward. He was a big man, scale-armoured, eyes hidden by his helmet. The long sword blade hissed through the air as the easterner aimed a mighty two-handed overhead blow. Ballista punched upwards with the boss of his shield. The impact almost forced Ballista to his knees. Instinctively, he drove upwards, thrusting his sword. The point slipped off the armour. The two men were locked together. Ballista cracked the pommel of his sword on to the back of the Sassanid’s helmet. The man grunted.

There was a deafening crack of thunder.

In the press of bodies, neither of the men could wield their blades. The Sassanid tried to bite Ballista’s face. Horrified, the northerner twisted back. The man’s beard scratched his cheek. Ballista dropped his sword. Its wrist strap dug into his flesh, the weight hard on his arm. He grabbed the plume on the Sassanid’s helmet; dragged his head back with a convulsive lunge, and Ballista headbutted his opponent. The metal ridge of the northerner’s helmet connected with the bridge of the man’s nose. Both their faces were running in blood. The crush of bodies pressed further.

A vivid flash of lightning illuminated the hellish scene.

The Sassanid had freed his sword arm. Overhand, he was sliding the tip of the steel over the rim of Ballista’s shield. Arms pinioned, the northerner struggled desperately. If only Maximus were here. The Sassanid set himself to thrust down into Ballista’s throat. He spat blood, broken fragments of teeth.

There was a surge of pressure from behind Ballista. Driven backwards, the Sassanid adjusted the angle of his sword. His mouth opened. More blood, pouring into his black beard. The sword fell from his hand. He looked down at the Roman blade driven into his armpit. His body went into spasm, became limp.

‘Gratius, Dominus.’ The legionary withdrew his sword. The corpse of the Sassanid fell underfoot.

‘I will remember,’ said Ballista.

A space had opened up. The Persians were giving ground. Another boom of thunder, and the rain began. It fell in heavy curtains. Ballista could feel it beating on his back. It was driving into the faces of the enemy.

‘One more step,’ yelled Ballista. He launched himself forward.

Ballista did not know if anyone was with him. His boots slipped in the water. No arrows came at him. The rain had soaked the bowstrings.

The Sassanid in front of Ballista looked around, hesitated, then turned and ran. Another flash of lightning lit the gloom. All the easterners were running through the rain.

Ballista laughed to be alive. If the gods wanted vengeance on the oath-breaker, they were biding their time.