‘Maybe, but that’s not going to be much of a consolation if they manage to batter the gatehouse down and swarm all over us.’

‘Couldn’t we try to destroy the onagers?’

‘How do you propose we do that?’

‘Send out our cavalry, charge over there before they can react and try to fire the onagers, or at least cut the torsion mechanism.’

Macro shook his head. ‘It wouldn’t work.There’s only one route for horses through the ground we’ve prepared with caltrops and pits, and that’s to the east. We’d have to take that until we were clear of the traps before we could turn towards the onagers.They’d have enough time to get plenty of men between us and their precious siege weapons. It’d just be a waste of men.’

‘What if we tried it tonight on foot?’

‘Much the same problem. There is a narrow passage through the obstacles to the west, and another to the north. If we lost touch with the paths we’d be caught between the enemy and our own defences. It’s almost impossible to find your way in the dark.’

However badly Cato wanted to destroy the onagers he knew that his friend was right. It would be a dangerous operation, by day or night. He ran a hand through his hair. ‘If we can’t stop these onagers then I suppose we’d better get the counter-measures in place.’

Macro nodded. ‘Let’s go.’

They strode away from the wall and Macro took a javelin from one of the auxiliaries. He stood to one side of the gatehouse, adjusted his position, and then began to mark out a line in the sand and gravel with the point of the javelin. He continued until he had described an arc round the rear of the gatehouse, and then he returned the javelin to the auxiliary.

‘That should do, Cato. I want a breastwork along that line. Build it up as high as you can. Rig a few sheltered platforms on either side. If the enemy comes through the breach then we’ll meet them with arrows and javelins from three sides. Got all that?’

‘Yes, sir.’

‘Then let’s get to it.’