‘Yes, sir.’ The soldier saluted and turned to leave the room. At once Cato threw back his covers and swung his legs over the side of his bed. By the light of a single lamp the soldier had left on his table he pulled on his boots, tied them up and stretched his shoulders before standing up. Then he lifted his chain mail over his head, collected his helmet and sword belt and went to join Macro. Outside headquarters the air was cold and the pale light of the stars provided just enough illumination for Cato to see the barracks on either side of the street as he made for the main gate. Faint glimmers of light showed round the door and window frames of some of the barracks as those auxiliaries who could not find sleep passed the time at dice, or carving, or the myriad ways that soldiers occupy themselves while waiting for action.

As Cato climbed up through the hatch of the gatehouse tower he saw Macro’s broad silhouette over by the breastworks.

‘You sent for me.’

‘Yes, I thought you should see this. Look out there.’ Macro extended his arm towards the enemy camp and pointed to an area, perhaps three hundred paces away, where several torches burned, casting a wavering patch of light. In front of the torches was a wicker barricade that concealed the activity beyond. But the sounds of hammering and the shouts of men carried clearly to the two centurions on the gatehouse.

‘Any idea what’s going on?’ asked Cato.

‘Could be knocking up some assault ladders, or a battering ram. Not that that worries me, unduly. They still have to cross the dead ground before they can get close enough to use that sort of equipment.’

‘Of course, they might be constructing something else,’ Cato mused.

‘That’s what I thought. Perhaps the Parthians have provided Bannus with a company of engineers.’

‘As well as arms and those horse-archers? That’s uncommonly generous of them. But then again, we’re all playing for high stakes.’

‘True. Well, there’s nothing we can do about it now.’ Macro turned away from the enemy camp and glanced at the opposite horizon. ‘It’ll be light soon. Then we’ll see what they’re up to.’

It was not long before the darkness began to dissipate and detail by detail the landscape around the fort became visible. Soon the enemy extinguished the torches and Cato, whose young eyes were better than Macro’s, strained to make out the details of two thick wooden frames beyond the wicker screen. Then, he felt a sick feeling in his guts as he realised what he was seeing. He waited a moment longer to be sure before he turned to Macro.

‘Onagers. Two of them.’