The Battle of Gaugamela, 331 BC

The Persian empire had stood for two centuries when Alexander of Macedon crossed into Asia to take it, and by the autumn of 331 BC the war had come down to one field: a plain in northern Mesopotamia called Gaugamela, near what is now Mosul in Iraq. Alexander was twenty-five. Darius III, the Great King, was waiting for him there, and if Darius lost this battle he lost the empire.

Darius chose the ground, which is the part people forget when they tell this as a story about genius.

He had lost to this boy once already, at Issus, on a coastal strip too narrow for his numbers to matter. So he found a wide flat plain and had it levelled: had the ground worked, physically, so that his scythed chariots would run clean and his cavalry would have room. He brought contingents from the whole eastern empire, Bactrians and Sakā and Indians with elephants, and he put around a hundred thousand men on ground he had prepared himself. It was, by every measure available to him, the correct plan.

Alexander had about forty-seven thousand and arrived late in the day, and did not attack. He camped in sight of the Persian army and slept. Darius, who could not know whether there would be a night attack, kept his whole army standing in formation all night in case there was one. By dawn one of those two armies had slept and one had been on its feet for twelve hours.

Then Alexander did something that only works if you have understood exactly what the other man wants. He advanced obliquely, edging his whole line to the right, walking his army sideways off the prepared ground. Darius had to follow, because the levelled strip was the point of his entire deployment, and following meant sending his cavalry out to the flank to stop the drift, and sending them out meant stretching his own line.

And a stretched line opens. Somewhere left of centre, as the Persian cavalry pulled wide, a gap appeared between the horse and the infantry beside them.

Alexander had been waiting for that since the previous afternoon.

The Companions went into it in a wedge, with him at the point of it, and the wedge is not decoration: it puts one man and one horse at the tip so the formation can enter a gap narrower than itself and widen it by arriving. They did not go at the Persian army. They went at Darius, straight down the throat of the opening, with the hypaspists coming in behind them, and the Persian centre came apart around the King.

Darius left. That is the whole of the outcome and it happened in perhaps a minute. Whether he fled or was carried off in a general collapse is argued about, and it does not matter, because the moment the King’s chariot turned the empire’s centre had nothing to hold to. Bessus, who commanded the left and was Darius’s own cousin, took his cavalry off the field intact, and would murder Darius himself the following year.

Alexander could not pursue at once, because his own left under Parmenion was being cut up badly and sent for help, and so the man who had just broken the Persian Empire turned around and rode back into his own battle to save his second-in-command.

The counts are worthless and I will say so plainly, because your own historians say it. Arrian claims three hundred thousand Persian dead and as many taken, which is more men than were present. Curtius says forty thousand. For the Macedonians, Arrian says a hundred, Curtius under three hundred, Diodorus five hundred. Somebody was lying, or somebody was guessing, or, most likely, nobody counted and everyone wrote the number that suited the sentence they were building.

I am not making a point about ancient sources. I am telling you that the difference between Arrian’s hundred and Diodorus’s five hundred is four hundred men, and that in every account of the most famous cavalry charge in history those four hundred exist only as the space between two numbers written by men who never met them.

One of them was crushed off his horse in the press behind the wedge and was finished with a javelin on the ground, and I went to him, and I was not in a hurry, because there was nowhere either of us needed to be.