‘Why are we not yet through, general?’ Xerxes asked, his voice carefully gentle.

Mardonius knew he was in danger and kept his head bowed.

‘Majesty, they are like devils. They have killed a great number of our men.’

‘I see. And how many of these Spartans have fallen?’ Xerxes replied.

Mardonius was not a weak man. Though he knew it might cost him his life, he answered firmly, praying the son had at least some part of his father’s strength of will.

‘Very few, Majesty, as far as I can tell. They are … unusually skilled. Our men could not break through.’

Mardonius had gone deep into the pass to watch the Spartans fight. He had come away ashen at what he had seen. Yet they were men, he told himself, not demons, not truly. They would grow weary, they had to.

‘The arrows had no effect on them?’ Xerxes was saying. ‘What are they, men of bronze?’ He laughed, but it was a brittle sound and it had fear in it.

‘They are disciplined, Majesty. They use shields and spears well. I truly cannot say if they lost men today.’

‘Pull the rest back – and interrogate them. Speak to those who faced these Spartans and learn all they know. Tomorrow, we will send in my Immortals. Have the entire baivarabam come to the front and make ready. At dawn, I will send all ten thousand in.’

Mardonius prostrated himself once more. He was not sure if his own command was in danger, or even his life, but it was the right decision and he did not hesitate. He had never seen anyone fight as well as the Spartan shield line. Mardonius had a vision of the Persian army slowly ground against them, a knife ruined on a spinning stone. The Immortals were the best soldiers of the empire, taken from every regiment and trained together as an elite. Only they could stand against the Spartans.

Xerxes dismissed his general without praise or comfort. It was already growing dark and at sea the fleets were pulling apart in grumbling truce, seeking safe harbours for the night. As he mounted up and trotted his horse to where the Immortals pitched their tents, Xerxes was not sure if he felt dismay or not. He had brought a vast army to give him the edge in a land he did not know. He had gathered a huge fleet to steal away any advantage they might have had on the deep waters. The losses to that point had not changed those truths. His army would crush the Spartans in the pass, if he had to spend a hundred thousand men to do it. His fleet would break through, if they had to lose two ships for every Greek trireme. An empire had resources enough to smother the Greeks, like crops drowned in a great flood. If Xerxes stood in the end in Athens, he would not care how many had died to put him there.