The Battle of Gaugamela (331 BCE)

The Battle of Gaugamela, fought on 1 October 331 BCE on a plain in northern Mesopotamia, was the last great battle of the Achaemenid Empire. Darius III chose and prepared the ground, brought scythed chariots, elephants and the cavalry of the whole eastern empire, and still lost to Alexander. The royal army scattered, Babylon and Susa surrendered, and the Persian heartland lay open.

Darius prepares a battlefield

After Issus and the loss of Phoenicia and Egypt, Darius III spent almost two years raising a new army at Babylon. This time it came mainly from the Iranian plateau and Central Asia: Persians, Medes, Parthians, Bactrians, Sogdians, Arachosians, Saka horse archers from the steppe, Armenians and Cappadocians, with some Indian troops and fifteen elephants. Heavy cavalry, some on armoured horses, was its strength. Darius also had about 200 chariots fitted with blades on the wheels and axles.

The lesson of Issus was that the Persian army needed space. Darius moved north and camped on the open plain near the village of Gaugamela, east of the Tigris, and had the ground levelled so that his chariots and horsemen could charge. Mazaeus, the satrap who had watched the Euphrates crossing, fell back before Alexander, burning the land, and Alexander crossed the Tigris unopposed in September 331.

An eclipse and a sleepless night

On the night of 20 September 331 there was a total eclipse of the moon. Babylonian astronomers recorded it in their diary, and Greek writers say it alarmed the Macedonian army. The diary is the nearest thing to a Persian-side document about the battle. It records the clash of the two kings’ armies, a heavy defeat, and that the king’s troops deserted him and fled to their homes. It is a record from Babylon, written by temple scholars, but it is not filtered through Greek eyes.

Darius expected a night attack. Arrian says Parmenion did propose one, and Alexander refused to “steal the victory”. The Persians, unable to fortify an open camp, stood in battle order through the whole night, so they went into battle tired.

The Persian battle order

Arrian’s description of the Persian line is unusually detailed, because the Macedonians later captured Darius’s written order of battle. Darius stood in the centre with his kinsmen, his guard of Persian spearmen whose spear butts were shaped like apples, Indian and Carian contingents, and the Greek mercenaries who were left to him. Bessus, satrap of Bactria, held the left with the Bactrian, Saka, Dahae and Arachosian cavalry. Mazaeus commanded the right with Syrians, Mesopotamians, Medes, Parthians, Armenians and Cappadocians. Chariots and elephants stood in front.

The battle

Alexander, outnumbered and facing a much longer line, advanced at an angle towards his right, edging away from the levelled ground. Darius sent cavalry from his left to stop him extending further, and fierce cavalry fighting began on that flank, where the Saka and Bactrians did well.

Then Darius launched the scythed chariots. Light infantry and javelin men in front of the Macedonian line shot the horses and pulled down the drivers, and the infantry opened lanes to let the remaining chariots run through harmlessly. The weapon that the field had been prepared for achieved little.

As more Persian cavalry moved to the left, a gap opened in the Persian line near the centre. Alexander turned his Companion cavalry and the nearest infantry battalions into it in a wedge and drove straight at Darius. Arrian says the king, seeing danger everywhere, was the first to turn and flee. Diodorus and Curtius tell it differently: Darius’s charioteer was killed by a javelin, his guards thought the king had fallen and began to break, and Darius was carried away in the dust and confusion.

The Persian right nearly wins

On the other wing the battle was going Persia’s way. Mazaeus pressed Parmenion so hard that the Macedonian left was close to breaking. A body of Persian and Indian cavalry rode through a gap in the phalanx and reached the Macedonian baggage camp, where Darius’s captured mother Sisygambis was held. Curtius says they called on her to come away, and she refused. Parmenion sent urgent messages for help, and Alexander turned back from the pursuit of Darius. On his way he collided with retreating Parthian, Indian and Persian cavalry in the hardest fighting of the day. When news of the king’s flight spread, Mazaeus withdrew, and Bessus led the Bactrians away in good order.

Losses and aftermath

Arrian claims 300,000 Persian dead, Diodorus 90,000 and Curtius 40,000. Macedonian losses are given as a few hundred. The Persian figures are guesses, but the defeat was total in its effect.

Darius rode through the night to Arbela, then fled across the mountains to Ecbatana in Media (modern Hamadan). Bessus and the eastern cavalry went with him. Alexander took the camp and the treasure at Arbela, and his army proclaimed him king of Asia. Within weeks Mazaeus surrendered Babylon and was made its satrap, and in December Susa opened its gates. What followed in Iran, from the Persian Gate to the burning of Persepolis, is summarised on Alexander the Great in Iran.

Why Darius lost

Historians usually point to three things. The Persian army was a collection of contingents that spoke different languages and fought in different ways, while the Macedonian army was a single professional force. Alexander’s movement to the right pulled the Persian line out of shape and created the gap he had waited for. And, as at Issus, the flight of the king ended resistance in the centre, because Persian armies were organised around the person of the king. Whether Darius fled first, as Arrian insists, or was swept away, as Diodorus and Curtius say, the result was the same.