It wasn’t glorious. But it was professional, and in three hours’ work, we’d broken the Thracian alliance at the cost of forty-one soldiers – a dozen cavalrymen from the first part of the charge, and thirty-nine Psiloi, and one – just one – pezhetaeros.

I have no idea how many Thracians we actually killed. I walked over the western end of the field and counted all the dead in one square a stade on a side, and then I measured the battlefield and multiplied by the number in the one square, and got four thousand, two hundred dead Thracians, which seemed high, so I put three thousand five hundred into the Military Journal. See? My handwriting. See the brown smear? I could barely write – and usually we put this sort of info on to wax and let the scribes copy it fair on parchment or papyrus, but that day the scribes were back with the camp and we were too far away to use them.

That evening, I got Alexander’s attention by the simple expedient of pushing into his tent, and asked to take the Hetaeroi back to cover the camp.

He had forgotten. He didn’t have Thaïs waiting for him. He was Achilles, lying by the fire with his loyal myrmidons all around him. Again, he’d led the hypaspists in person, and they lay around him like mastiffs. Was I jealous?

You bet I was. I missed them.

Alexander looked at me. Nodded. ‘Thanks,’ he said. He was going to say something more, and then I think the king took over from the man.

I took half the Prodromoi and all my squadron and rode off at the start of the sunset, and by full dark we were riding into our main camp, which we found terrified but sound. They’d seen some fugitive Thracians and been scouted by a mounted force, so I dismounted my troopers and sent Cleomenes back – alone – to warn Alexander. We spent a bad night on guard duty – two war parties brushed us and we held them.

At first light, the hypaspitoi came, led by Alexander in person. He looked at the signs of fighting and led the Prodromoi out himself, and came back two hours later.

‘They’re still out there,’ he said angrily. I think he felt that after two shattering defeats the Thracians might have the good grace to bend a knee and give in.

I was getting a different picture. What I saw was an enemy so diffuse and ungoverned that we couldn’t ‘beat’ them or intimidate them as a group. In effect, I was beginning to believe that we’d have to defeat every individual Thracian – at least once. Or perhaps just kill every one of them.

The next day, the army was reunited with the camp and we moved out to the north, to the banks of the Danube, where by Alexander’s usual combination of brilliant planning and ferocious good luck, the fleet lay rocking in the rapid current, tied to giant trees along the bank.

In the middle of the wide river, like a small ocean, lay the rocky shores of Pine Island, where eight thousand Thracians waited with their animals and their treasure. Beyond, at the very edge of sight, lay the far shore.

Right at our feet were the palings of the bridge that Darius had built in the years before Marathon, when he took a mighty army on to the steppes, and lost.

With a sinking feeling, I listened to the king and realised that he intended to march on – to take us on to Pine Island, crush the refugee Thracians there and then across the Danube, like Darius.

‘Darius lost!’ I found myself pointing out, later that evening.

No one else seemed to care, and a lot of wine was drunk. The appearance of the fleet, thousands of stades from home, was like a miracle, and it, combined with two fine victories, raised Alexander’s spirits to a fever pitch.

He ordered the cavalry to collect every boat and dugout canoe along the banks for two hundred stades, and I spent the next week riding up and down the river, ducking javelins, arrows and thrown rocks. The woods were full of Thracians, and I was in a fight nearly every day – my sword arm was a mass of scars.

The only day I remember was rainy. I was soaked to the skin when I rode back into camp, fifty canoes richer, and I stripped naked because Thaïs had a bath ready for me. She got me into the bath, helped me scrub the pain away and got the rolled linen off my sword arm in the hot water so that the pain was bearable, and then she told me she was pregnant.

I think that was the only time I’d seen her afraid. She was afraid of the pregnancy and afraid, too, of me.

I was delighted. But I remembered what had happened to Nike, and I was . . . afraid. So we had a fight – isn’t that what people do when they are afraid?

And in the midst of that fight – me in a tub of hot water, blood flowing from my arm, Thaïs and her woman trying to bandage me while we shouted at each other – Cleitus came in.

‘The king wishes you to attend him immediately,’ Cleitus said, his face deadpan.

‘Tell him I’m bleeding like a fucking sacrifice and naked as a baby,’ I shot back.

Cleitus shook his head. ‘No, Ptolemy. I will not. Come. Now.’

Things had changed a great deal. There had been a time when no one would have jumped like that for Alexander. We loved him – but we treated him as the first among equals. That was gone, now – even for Cleitus.

I got out of the bath, and Thaïs rubbed the water off me with her own chiton and pulled one of mine over my head. ‘Go,’ she said.

I really loved her. Then more than ever.

Alexander was sitting on a stool in his tent, with a low table made by two raw boards laid across two more stools – iron stools, taken as loot.

‘When I ask for you to come immediately,’ he said, and then he raised his head and saw the blood running down my right arm.

‘I was having my wound dressed, and having a fight with my hetaera, my lord. I apologise for being late.’ I suspect my sarcasm was all too evident.

He looked at me for a long time. His eyes were red, and he hadn’t slept, and Hephaestion looked like a corpse with a skull for a head.

‘I have fifty more canoes, and I lost three men over the last two days.’ I shrugged. ‘Aristotle would reduce this campaign to a mathematical equation. If we kill Thracians at this rate, we’ll still run out of highly trained Hetaeroi before they run out of ignorant savages.’

Alexander drank some wine. ‘You are dismissed,’ he said.

I turned and left the tent. I relate this to show that it was not all wine and roses. Alexander had launched four attacks against Pine Island – you won’t find this in the Military Journal – and been pushed off every time. The last time he’d got ashore in person, certain that his men would walk on water to save him. Instead, he’d almost been overrun, and twenty hypaspitoi had died saving him. Two full files. Dead.

Alexander probably summoned me to order me to lead the next assault. I was mouthy and he dismissed me and summoned Perdiccas, and he went and got wounded in the arm and the hip so that he was out for the rest of the campaign.

The next day it was Cassander’s turn. He went and got knocked unconscious by a blow to the throat that left him unable to speak for days. No great loss.

I brought in more canoes and lost another trooper in the endless fighting, out there in the woods. And I learned from prisoners that the Getae, the largest, fiercest and best-mounted tribe of Thracians – not really Thracians, but a sort of mixed bag of Thracians and Scythians – were present in force on the far bank, with a fortified camp and at least ten thousand horsemen. They were feeding the Thracians on Pine Island.

When I returned, I heard about Cassander, and I went to Alexander’s pavilion and was admitted.

‘I’m sure you have a great deal to tell me, Ptolemy,’ Alexander said bitterly.

I realised that he was drunk. But I told him about the Getae, anyway.

He snorted. ‘Barbarians. They won’t stop me. I’ll have Pine Island, I’ll build a bridge like Darius and we’ll march across.’