He tensed, wondering what it was that had made the soldier shout. It wasn’t that the enemy was approaching; the large force was still assembled at the limits of vision.

Then, peering into the distance, he realized.

A haze of yellow dust had begun to color the sky where before it was a pure shade of blue. It came from nothing: there was no wind. In the midst of the enemy, a fierce light suddenly flared. As the light shone brighter and brighter, the haze became a thick cloud, filled with swirling particles of grit. A sandstorm was gathering, rising higher, becoming thicker, until soon the enemy couldn’t be seen at all.

Agathon and the general exchanged stunned glances.

So close to the desert, sandstorms struck the city occasionally, but Agathon had never seen anything like this. Without wind . . .

Wait. He realized there was a wind.

The still air gave way to a steady breeze, causing the orange flags carried by the standard bearers to snap and crackle. The growing wind whipped at Agathon’s loose trousers and blew his long hair around his face as it became stronger. Soon it was howling with sudden ferocity.

Dust and sand billowed above the plain. There was no way to say where the enemy was or what they were doing. Squinting into the storm, Agathon felt tiny grains strike his exposed face and he jerked his head violently when sharp grit flew into his eyes. He ducked his head and shielded his eyes with his hands, blinking as tears trickled down his cheeks.

Over the sound of the wind he could hear his soldiers muttering prayers to the gods, while others called out to their companions, asking what was happening.

‘Hold your posts!’ General Dhuma bellowed. ‘No one leaves these walls!’

As it became almost impossible to see, Agathon copied the soldiers around him and sank to one knee, burying his head into his chest. The defenders fought their own private battles with the sandstorm, and at the forefront of every man’s thoughts was the notion that surely the timing was too close to be coincidence. Agathon remembered the stories about the dozen foreigners who wore robes and carried strange staffs.

No, he told himself. The wind would die down. Long-lasting sandstorms needed days to build up their strength. It would soon pass.

Yet time dragged on, and if anything the wind gained in power. Agathon occasionally heard Dhuma’s voice roaring over the storm, telling the defenders to stand fast. His cries were like a beacon on a dark night, providing hope that someone else was out there.

But then the general gave a command that caused Agathon’s heart to beat out of time.

‘To arms! We’re under attack!’