The cold bit at a Macedonian throat on 1 October 331 BC, and the weight of a sarissa sat in the hand like a promise. Ahead of Alexander the Great, the plain by Gaugamela had been levelled for Persian scythed chariots, near Arbela in what is now Iraqi Kurdistan, north of modern-day Erbil. On the other side stood King Darius III, waiting with a host drawn up to end the war.

This was the second and final battle between Alexander and Darius, and it came after years of hard marching. In November 333 BC, Darius had already been beaten at Issus, where his wife, his mother Sisygambis, and his daughters Stateira II and Drypetis were taken. Alexander then broke Tyre in 332 BC, took Gaza, and received Egypt when the satrap Mazaces surrendered without a fight. By the summer of 331 BC he was moving from Egypt through Syria towards the Tigris, while Darius tried diplomacy, then a ransom, then offers of land and co-rule. Alexander refused every time.

At Gaugamela the odds were brutal. Arrian gives Darius 40,000 cavalry and 1,000,000 infantry, though other ancient writers give lower but still vast numbers, with 200 chariots and even 15 war elephants. Alexander had about 7,000 cavalry and 40,000 infantry, including the phalanx, Thessalian horse, Paeonians, Thracians, Agrianians, and Greek mercenaries. Parmenion held the left, while Alexander took the right with his Companions. Darius placed Bessus on one flank and Mazaeus on the other, with his own position in the centre.

Alexander advanced in echelon, pulling his right outward to tempt the Persian horse away from the prepared ground. The Scythians struck first, then Bactrians, and the fighting on the Macedonian right became a long cavalry struggle. Darius loosed his scythed chariots, but the Agrianians and javelin-men broke many of them, and the rest passed harmlessly through gaps opened in the ranks. Then Alexander gathered his Companions into a wedge and drove for the centre itself, straight at Darius and the royal guard.

That was the decisive hour. Darius saw the gap opening and fled first, and the Persian centre began to collapse. Yet the victory was not clean enough for glory alone. Parmenion sent desperate messages from the left, where his wing was hard pressed, and Alexander turned back rather than chase Darius into the mountains. The Persians who broke through the Macedonian line rode for the camp to loot, even trying to reach Sisygambis, but she would not go with them. Sixty Companions were killed, and Hephaestion, Coenus, and Menidas were wounded.