Cato felt a bitter acid taste in his mouth as he swallowed. 'That's what'll be in store for any of us they take alive, I imagine.'

'Yes,' Macro replied softly. 'Bannus is trying to get the wind up our boys.'

'Then I think he's succeeded.' Cato glanced along the wall and saw one of the auxiliaries bent over, vomiting on to the catwalk.

'Of course,' Macro continued flatly, 'there's a nice ironic touch there for his own side. After all the rebels we've crucified over recent years, now we're on the receiving end. Listen to 'em! They just love it.'

As the last cross rose up the enemy cheered loudly, and then their tone quickly changed to cruel laughter and derisive taunts and jeering as their victims writhed in agony and blood ran down beneath their arms and stained their bare chests bright red.

'They've had their fun,' Macro growled. 'Now it's our turn. Archers!' He turned to the men on the wall. In amongst them were sections of men armed with compound bows.'Archers! Shoot on that crowd! Shoot, damn you!'

His obvious rage spurred the men into action. After hastily stringing their bows, the fastest of them notched their arrows, drew back the strings and angled the shafts high before releasing them. The first, ragged volley fell into the crowd, taking down a handful of the enemy before they could scatter and run for cover. More were struck down as the arrows fell with increased intensity. Then a shaft struck one of the Romans on the crosses, burying itself in his throat, so that he jerked, struggled a moment and then hung limp and quite still.

'They're hitting our men!' Cato said in a horrified tone. 'Stop them!'

'No.' Macro shook his head. 'That's what I'd hoped for.'

Cato turned and stared. 'What?'

Macro ignored him and turned to shout to the archers. 'That's it, boys! Keep it up! Stick it to 'em!'

The archers kept shooting as fast as they could, and had no time to follow the passage of their arrows, and so were unaware that they were hitting their comrades at first. Macro waited until the enemy had dispersed and the prisoners had been silenced before he gave the order for the archers to cease shooting. Only then were they fully aware of the result of their handiwork, and they gazed towards the enemy lines in numbed silence, until Macro's bellowed order echoed across the fort.

'First century will remain on watch! All other centuries to breakfast!'

When the men moved away from the wall slowly Macro thumped his fist down on the parapet. 'Officers! Get your men moving! They're not paid by the bloody hour!'

He glared at the officers as they hurried to carry out his command and soon only a thin screen of auxiliaries remained, spread along the wall. Then Macro nodded with satisfaction. 'I don't want our men exposed to that display any more than necessary. I want their minds on the fight, not on what might happen after it.'

'If they know what Bannus has in store for them, then they'll fight to the death.'

'Maybe,' Macro replied. 'But they'll not fight as well, if I give 'em the chance to dwell on the fate of those poor buggers.'

Cato could see the sense of that. Macro had demonstrated a fine understanding of how soldiers' minds worked, and even if the men at Fort Bushir were doomed Macro would see to it that their minds were concentrated on killing as many of their enemies as possible before they were cut down in turn. His friend was professional to the very last, Cato realised. And, at some point in the next few days, there was every chance that that last moment would indeed come. Cato looked back towards the bodies hanging from the crosses.

'Was it really necessary to kill them?'

Macro sniffed. 'What would you have done? Left them there to die a slow, agonising death? It was an act of mercy, Cato.'

Cato frowned as an unpleasant thought entered his mind. He turned to his friend. 'What if I had been captured along with Sycorax and the others last night? Would you have given the order for the archers to shoot me?'

A bemused look flitted across Macro's face.'Of course I would, Cato.Without an instant's hesitation, and believe me, if you had been nailed up alongside those men, you'd have thanked me.'

'I'm not sure about that.'

'In any case, I wouldn't have given you the choice.' Macro smiled grimly, before he continued in an earnest tone, 'And if it had been me out there, I'd have expected you to do the same.The thing is, I'm not sure you'd have the balls to go through with it… Well?'

Cato looked at him for a moment and then shook his head. 'I don't know. I just don't know if I could do that.'

Macro pursed his lips sadly. 'You're a good man. A good soldier, and a good officer most of the time. If we get out of his, then one day you'll have a command of your own, and I won't be there. That's when you'll have to make the really tough decisions, Cato. You can count on it. The question is, are you ready for that?' He looked hard at his young friend for an instant and then punched him lightly on the shoulder. 'Think it over. Meanwhile, I want you to make sure that the gatehouse is as ready as it can be before Bannus gets that onager back into action.'

'I don't think there's any point to that, sir. He'll batter our repairs down quickly enough.'

'The point is that it keeps our men busy, and stops them thinking too much.That includes you. It also shows Bannus and his friends that the Second Illyrian's not going to give up, roll over and wait for our enemies to stick the boot in.We're better than that. Understand what I'm saying?'

'Of course,' Cato replied testily. 'I'm not a fool.'

'Far from it. But even the most brilliant minds can still learn something from those of us with experience, eh?' Macro smiled. 'Now see to it that you do a decent job of that breastwork.'

'Yes sir.' Cato nodded. 'I'll do my best.'

'Of course you will. I'd expect nothing less. Don't just stand there, Centurion. Get moving!'

All morning the men toiled at raising the breastwork over the remains of the gatehouse, and strengthening the inner wall. Mindful of Macro's words, Cato drove them hard and permitted them few rest breaks as they thickened the makeshift defences and added to the height of the inner wall. If the enemy managed to force their way through this last obstacle then the Second Illyrian Cohort would be wiped out. As the men toiled within the fort, the enemy continued to clear away more of the traps laid outside, their workers screened by a thin line of archers ready to take a shot at any target that revealed itself up on the wall. Behind them the engineers sweated under the bright sun to make the surviving onager serviceable once again. Shortly after noon the enemy at last drew away from the siege engine as the throwing arm was carefully ratcheted back, engineers checking the weapon for any further sign of damage as it prepared to bombard the fort again. At length they were satisfied that it was safe to proceed. A curt order was shouted, the locking lever snapped back and the throwing arm swept up and hit the cross beam with a loud thwack as the missile was released, soaring up into the air and then arcing down towards the gatehouse. At once Cato and the work party dropped their tools and scrambled down behind the wall into cover.

The Parthian siege engineers were first rate, or at least very lucky, thought Cato, as the first shot smashed into the breastwork and knocked a gaping hole in the top of the rebuilt defences. The bombardment continued with an endless cycle of clanks, a crack and the crash and rumble of masonry. After the first missile had landed, Cato pulled his men back behind the inner wall and climbed a corner tower to watch proceedings as the hot afternoon wore on. The gradual destruction of the remains of the gatehouse was carried out in a methodical and complete manner, beginning with the wall and then simply pounding the rest into a pile of loose rubble that would make a practical breach for Bannus and his army to assault. As the light began to fade and the desert sand shimmered hot and bright red in the wash of the setting sun, the onager at last fell still and the men inside the fort no longer had to press themselves into the shelter of a wall and cringe as the rocks crashed down.When he was sure that the bombardment had ceased, Cato sent for Macro. The prefect joined him behind the destroyed gatehouse and took a few tentative steps on the rubble.