Pyrrhus rode in after dark with four men. He had a claim to having been the bravest of the Hetaeroi, and the king embraced him – it turned out that he’d ridden through the Medes and kept going – with just half a file – sweeping through the Phrygians before realising that no one was behind him. He’d escaped down the Persian bank of the river, and he admitted that he’d been unpursued. The Medes had been shocked by the cavalry action.

We were up well before first light. We crossed the marsh south of the lake on trails marked by the Agrianians and pushed north – crossed the Granicus almost dry shod, where long bars of stony shale lay across the water like piers or bridges.

We were fast and silent, but Arsites was no fool, or perhaps it was Memnon. Either way, the lack of fires probably gave us away, and the Persians sent cavalry probes across the Granicus at first light, and these found us – they on our side of the river, and we on their side. They galloped off, and we couldn’t stop them, and the game was up.

So the king led us on faster. I was on Penelope, saving Poseidon for the last possible moment. Polystratus had him in the rear of my squadron. Philotas rode six files to my right – he was commanding the Hetaeroi, and I was reduced to a mere king’s bodyguard. He hadn’t said a word to me all morning. I’m certain we both had the same thought – no need to quarrel, when with a little luck the Medes would kill one of us.

Arsites formed his army to his own left – which is to say, he now formed with his Greek mercenary infantry on that low ridge, and the far right of his cavalry (the western end of his line) covered by the river, and his left-flank cavalry dangled at the eastern end, but because he had fifteen thousand cavalry to our six thousand, his left flank overlapped our right.

On our far right, in the bushy ground to the east, Alexander set the Agrianians and all the archers under Attalus. Next in line came Philotas with a thousand Hetaeroi, and then the king in the centre of the right, with his bodyguard, and then Arrhabaeus, the scrawny sod, another of Parmenio’s old men, with the rest of the Hetaeroi. To our left were the hypaspitoi and then all six taxeis of the pezhetaeroi – ten thousand of them, the largest phalanx I’d ever seen formed in one place.

And on the far side of the phalanx was Parmenio with all the Thessalian cavalry, all the Greek allies, including your father, and all the Thracians.

Opposite us, as we formed, we saw Arsites trot into position facing us. He moved twice, so insistent was he in lining up on Alexander. He had almost two thousand Persian noble cavalrymen – in effect, men as good as our Hetaeroi. The rest of his wing was composed of Hyrkanians and Phrygians, and on their far left they placed six hundred mercenary Greek cavalry under Memnon himself. Thebans, a lot of them, and Thessalian exiles and Athenian exiles – men with every reason to fight well.

Alexander rode along the front of the whole army as it formed, so that we appeared to be in a state of chaos, with regiments spread over forty stades in every direction. In fact, we had a standard formation and we’d practised it almost every day since we left Amphilopolis. Every man and every file knew his place, in rain, in snow, in fog. As soon as the order was given to the marching column to form line of battle, units marched to their places and pushed left or right to make sure they had room. Files opened and closed – cavalry units added or subtracted files to fit into the line.

And as this unfolded, the king rode from unit to unit, calling men by name and shouting encouragement. He didn’t restrict himself to units that loved him – he rode to every unit, even the taxeis that had been Parmenio’s in Asia, and to every group he called out, ‘Tonight we will be rich men!’ and they always cheered.

We rode with him, of course, and he rode fast, and I was glad I was still on my riding horse. We cantered from unit to unit, and then, when we’d reached Parmenio on the far left, we halted.

‘You ready, lad?’ Parmenio asked.

Alexander’s head snapped back as if he’d been hit.

‘Lad?’ he asked. ‘I’m your king.’

Parmenio smiled. ‘Your first real battle,’ he said.

Alexander sat back – spine straight, posture perfect, rein held loose. ‘Parmenio, if I win this battle, will you concede that I know my business?’ he asked.

Parmenio laughed. ‘Relax, lad. Take it easy. We have the numbers, and their Greek foot are no match for our pikes – our phalanx is twice the size of theirs. Nothing to worry you.’

‘When I beat them, I’ll execute every one of the traitors,’ Alexander said.

Parmenio smiled. ‘What a fire-breather you are, to be sure. Best get back to your wing. Arsites has decided to come at us.’

Sure enough, Arsites and his wing were advancing.

Alexander looked, turned his horse and we galloped across the whole front of the army.

No one else seemed to know we were late – men cheered just to see the king ride so beautifully, his cloak flying behind him, back straight, as if he were an equestrian statue brought to life. The rest of us followed as best we could – Black Cleitus, me, Nearchus, Marsyas; Laodon and Erygius, and older men like Demaratus of Corinth. In some ways, despite being a nation of innovators, Macedonians are very old-fashioned – in a big fight, we like to see a king go into battle surrounded by his closest friends. I’ve met dozens of Greeks who accuse Alexander of living like a hero in the Iliad– what they fail to understand is that allMacedonians live like heroes in the Iliad.

We hauled on our reins when we got back to the Hetaeroi. Polystratus was ready for me – I changed horses and buckled the cheek-plates on my helmet, and took my heaviest spear from Ochrid, who gave me a grin.

Arsites and his whole line were a stade away.

The king looked left and right down the line.

He pointed to Arsites, easily visible a stade or less away on a magnificent white horse.

‘Blow through them and the battle is won,’ he said. ‘Thank the gods that they were fools enough to fight.’ His personal priest and diviner, Aristander, offered a sacrifice and a libation, and exclaimed at the sight of the liver – he shouted aloud, he was so excited.

‘Victory!’ he shouted. He waved the bloody liver.

All the time Aristander was killing his beasts, the Persian line was advancing.

They weren’t Macedonians. Gaps began to open in their line as soon as they rolled forward. Indeed, the largest gap opened between the wing facing us and their cavalry in the centre. They’d put Paphlagonian or perhaps Phrygian cavalry in the centre – I couldn’t tell which – screening the Greek mercenaries to their rear. Why they placed cavalry in opposition to our phalanx I’ll never know.

But their cavalry had no intention of riding forward into our sarissas, so the centre lagged behind and Arsites’s wing plunged forward, and a gap began to open. An enormous gap.

The king waved to us, his bodyguard. ‘Hold here,’ he said.

He shouted orders to Philotas and waved at Arsites.

Philotas protested.

Alexander insisted.

Philotas shrugged, obviously angry, and barked orders at his trumpeter.

And our entire right division began to move.

Philotas didn’t want to do it. It was written in every line of his body – in the way he rode. But I don’t know what else he wanted to do.

He rolled forward with half our cavalry, and three horse lengths from the enemy, he flashed his sword and the Hetaeroi went straight to the gallop – a tactic we practised on a thousand strips of grass, in winter and summer – and the enemy were caught by surprise, suddenly turned from aggressive attackers to defenceless prey.

Then I could see nothing but the sudden onset of dust – the battle haze of the poet.

Arsites was no longer opposite us. Something else had caught his attention, and he’d taken his bodyguard out of the line. But we could still see Persian cavalrymen in beautiful tall helmets opposite us. They were rolling into the melee – fighting draws men like a magnet.