His men stood still, one at each weapon, holding the lever that would release the grip on the torsion rope. The centurion waited until he was certain the leading ranks of Nubians had ridden over the place where the first bolt had plunged into the ground. Cato was gripped with impatience as the centurion kept his arm aloft and continued to let the enemy draw closer.

‘Get on with it, man,’ he whispered harshly.

‘Release!’ the centurion suddenly bellowed, sweeping his arm down. The cracks of the bolt throwers sounded almost together, like the snapping of a fistful of sticks. Thirty small shafts whirred towards the camel rider unit, some five or six hundred strong, Cato calculated. The centurion had timed his order well and not a single shot fell short as the cruel iron heads of the missiles tore through the sandy hides of the camels and the robes of their riders. The stricken animals collapsed in heaps as their spindly-looking legs gave way and those behind them were forced to swerve aside, into the flanks of their companions, disrupting their move against the waiting Romans. For a moment their advance stalled, and then as the Romans reloaded their weapons, the Arabs worked round their casualties and continued on. The second volley shot out from behind the Roman lines and struck home, killing and wounding several more. Some of the riders proved a little wary of leading the charge and lagged behind, no doubt hoping to avoid the further attention of the artillery crews. The third and fourth volleys stopped the enemy dead, and they stood in some confusion as the bolts landed amongst them, and then the fifth volley broke their will. The commander of the unit turned aside and rode off towards the flank, beckoning his men to follow him.