The Sassanid drew his bow.

Naulobates made no move to defend himself. None of the Heruli moved to protect him.

The Persian selected a long cane arrow from his quiver. With slow deliberation, he nocked it, raised the bow, and drew the string to his ear.

Valens watched, frozen with incomprehension.

The Sassanid aimed at Naulobates’s chest. No fur jacket would deflect the missile.

The King watched the archer.

The Persian lifted the bow to the skies, and loosed. The arrow flew high over the Heruli hoard.

‘We have fought the Sassanids before,’ Aruth said. ‘It is their way. Now we will show them ours.’

As the nobleman cantered back towards the bear standard of the Satrap of Hyrkania, the lines of the Heruli parted. Two tribesmen trotted their ponies out. Behind and between them stumbled a naked man. He had the malformed skull and red-inked skin of one of the Rosomoni. A rope was tied around each of his wrists. The end of one rope was secured to the horns of the pony on the left, the other the one on the right. The riders kicked on to a canter. The naked man was jerked off his feet. For a time they dragged him about between the two armies. Valens winced as the ground tore the man’s flesh.

‘Spare him no sympathy,’ Aruth said. ‘In the hunt we drove a boar from its lair. That man dropped his spear. He endangered the brothers around him. Already his suffering brings the favour of the gods.’

Naulobates uttered a thin, high command.

The riders moved to a gallop, then peeled off right and left. The ropes snapped taut. The momentum of the ponies was halted. The riders whipped them on. With a horrible wet rending sound, one of the prisoner’s arms was torn from its socket, and ripped away from his torso.

The horsemen cut the ropes, left the severed limb and the man bleeding his life away.

Naulobates turned to Valens. His grey eyes were untroubled. ‘Good weather for the fight.’

Valens looked at the heavens. A bank of dark clouds were coming down from the north. ‘Will the rain not dampen your bowstrings?’

‘Oh, yes.’ Naulobates beamed. ‘But that is nothing. The gods draw close. On the Steppe there is nothing better than to fight under a storm, while the sky above your enemies is clear. There is no doubt we will be victorious.’

Valens wished he shared the confidence of the Heruli king.

Trumpets sounded along the Persian lines. The Sassanid light horse jumped into their saddles. At a walk, the whole host began to advance.

Naulobates threw back his head, and made an unearthly sound.

Yip-yip-yip. The weird war cry was taken up by all the Heruli.

As one, the nomads mounted. Valens and the other Romans scrambled onto their horses.