Shifting his position on the damp ground – all his joints ached – he studied the fortress with the eyes of a professional soldier. It was large and rectangular, raised on an earth platform, and set behind a wide ditch filled with water. The mud-brick curtain walls were tall and broad. Even so, it would not hold out long against a besieging Roman army. The corners of the fort were not rounded, but square. Stone-throwing artillery would soon expose that weakness and bring them tumbling down. There were no projecting towers along the walls. Once the moat had been filled in, attackers with siege ladders could reach the wall without being exposed to any missiles except from ahead. If archers and bolt-throwers kept the defenders’ heads down, a storming party should reach the breach almost unscathed. Of course, after that, it would be the usual terrible work, step by step up the rubble, close to the steel.

The deficiencies of the fortress would make little difference against the nomads. The tribes on the Steppe were far too primitive to ever undertake regular siege works. Yet somehow the slipshod construction offended his sensibilities. It was typical of Persian indolence.

His gaze tracked west. Some four miles of reed beds and marshes separated the fortress from the Caspian. Narses had said a levee linked two wooden lookouts to the walls. The Persian claimed that when the sea had retreated, the land left behind was too soft to support heavier defences. That was another example of eastern idleness. A good Roman engineer would have sunk deep pilings, poured concrete in reinforced foundations, and extended the barrier to the waters’ edge.

Gods below, he was tired. He was too old for this life. They had been a long time in the saddle.

The enemy swarming over their hastily abandoned camp had indeed seen them when they left the cover of the willows. That damned trumpet had rung out, and shrill, ululating calls had come across the plain.

They had gone north at a gallop, flat out.

There had been nothing else for it. They could not have made much speed down in the bed of the river, and, racing down the banks, the Persians would have soon run them down.

The going was good. Their horses were fresh, and those of the Persians already worn by half a day’s forced march. Soon they had opened a lead of almost a mile. The cries of easterners were as faint as distant birds. Only the note of the trumpet had cut clear above the thunder of their own horses.

And then the storm had descended. Huge black clouds trailing tendrils of rain rolled down from the north. In an instant they were soaked to the skin, but the visibility was cut to no more than two hundred paces, and the trumpet could be heard no longer.

They had slackened their pace to a fast canter to preserve the horses.