Battle of Gaugamela (331 BC): The Fall of the Persian Empire

The Battle of Gaugamela, fought on 1 October 331 BC on a plain in northern Mesopotamia, was the decisive victory of Alexander the Great over the Persian king Darius III. Facing a far larger army on ground chosen by his enemy, Alexander broke through the Persian line and put Darius to flight for the second time. The battle brought down the Achaemenid Empire, which had dominated the Middle East since Cyrus the Great, and made Alexander king of Asia.

Background

After his defeat at the Battle of Issus in November 333 BC, Darius III had offered Alexander money, territory and a marriage alliance, and been refused. While Alexander spent 332 BC besieging Tyre and Gaza and taking Egypt, Darius assembled a new royal army in Babylon, drawing troops from the eastern provinces of the empire: Bactrians, Sogdians, Arachosians, Indians and Scythian allies, as well as Persians, Medes and Babylonians.

In the spring of 331 BC Alexander left Egypt, returned to Tyre and marched inland. He crossed the Euphrates at Thapsacus in midsummer and, rather than taking the direct route south to Babylon, moved north-east towards the Tigris, where he would find supplies and cooler country. He crossed the Tigris unopposed in September.

On the night of 20 to 21 September 331 BC a total eclipse of the Moon was seen. Alexander’s seers interpreted it as a bad omen for the Persians. The eclipse is important to historians because it allows the battle, said to have occurred eleven days later, to be dated precisely.

The battlefield and the armies

Darius chose a broad, open plain near a village called Gaugamela, now usually identified with Tell Gomel, north-east of Mosul. He had the ground levelled so that his scythed chariots and his large cavalry could operate freely. He also had around 15 war elephants, though they seem to have played no part.

Ancient writers give enormous numbers for the Persian army: Arrian says 40,000 cavalry and a million infantry, and other sources give figures between 200,000 and over a million. These totals are impossible to supply on a single battlefield, and historians generally estimate between 50,000 and 120,000 men, with a very strong cavalry arm. Darius’s army was a true imperial levy, organised by peoples. Arrian, drawing on a captured Persian order of battle, lists contingents from Bactria, Sogdia, Arachosia, Persis, Media, Parthia, Hyrcania, Babylonia, Armenia, Cappadocia and Syria, along with Saka horse archers from Central Asia and Greek mercenaries, now much fewer than at Issus. Many of these troops had never faced the Macedonian phalanx before.

Darius commanded from the centre, surrounded by his royal guard and kinsmen, with Bessus, satrap of Bactria, leading the left wing and Mazaeus, a senior noble, leading the right.

Alexander had, according to Arrian, about 40,000 infantry and 7,000 cavalry. Modern historians accept these figures as broadly reliable. It was a veteran army, reinforced since Issus by fresh troops from Macedonia and Greece, and it was confident after three years of almost unbroken success.

The night before

When the armies came into view, Parmenion advised a night attack to offset Persian numbers. Arrian and Plutarch report that Alexander refused, saying he would not steal his victory, although Arrian notes that the decision was also sensible, since fighting in the dark in unknown country was risky. Alexander spent the previous days reconnoitring the ground himself, and he rested his troops in a fortified camp a few kilometres from the Persian line. Expecting a night attack, Darius kept his army standing in arms through the night, which left them tired at dawn.

What happened

Because the Persian line was much longer than his own, Alexander arranged his army in two lines, with the second ready to face about and fight if surrounded, and with flank guards angled back on both wings. He led the Companion cavalry on the right; Parmenion held the left with the Thessalian cavalry.

As the battle opened, Alexander moved his whole line obliquely to the right, away from the levelled ground. To stop him reaching rough terrain, Darius sent cavalry from his left to outflank him, and a long, hard cavalry fight developed on the Macedonian right. Darius then launched the scythed chariots. Alexander’s javelin men and archers struck down many horses and drivers, and the infantry opened lanes through which the rest passed and were dealt with behind the line.

As more Persian cavalry moved out to the left, a gap opened in the Persian line near its centre. Alexander formed the Companions and nearby infantry into a wedge and drove into the gap directly towards Darius. As at Issus, Darius fled, and the Persian centre and left began to give way.

On the other wing the fight was much more dangerous for the Macedonians. Mazaeus’s cavalry pressed Parmenion hard, while some Persian and Indian horsemen broke through a gap in the phalanx and rode to the Macedonian baggage camp to plunder it and free prisoners. Parmenion sent for help. Alexander broke off his pursuit of Darius and turned back, fighting a fierce action with retreating Persian cavalry on the way, but by the time he arrived the Thessalians had held their ground and the Persian right was withdrawing.

Ancient writers were divided over this episode. Some, followed by Plutarch, blamed Parmenion for being slow and timid and claimed his call for help cost Alexander the chance to capture Darius. Modern historians often see this as later propaganda against Parmenion, who was killed on Alexander’s orders in 330 BC, and note that his wing faced the strongest Persian cavalry for most of the battle.

Alexander then resumed the pursuit, riding as far as Arbela, about 100 kilometres away, where he captured Darius’s chariot, bow and treasure. Darius himself escaped east into Media.

Losses

Arrian claims 300,000 Persian dead, Diodorus over 90,000 and Curtius 40,000; all are probably exaggerated. Macedonian losses are reported as about 100 men (Arrian) to 500 (Diodorus), with Arrian adding that over 1,000 horses were lost. Many historians think Macedonian casualties were higher than reported, especially on Parmenion’s wing.

The table sets out the main figures; the ancient claims for the Persian side are not reliable.

Key people

• Alexander the Great (356-323 BC): king of Macedon, aged 25.
• Darius III (ruled 336-330 BC): the last Achaemenid king of Persia.
• Parmenion (c. 400-330 BC): commander of the Macedonian left.
• Bessus (died 329 or 328 BC): satrap of Bactria, leader of the Persian left, later Darius’s murderer.
• Mazaeus (died 328 BC): commander of the Persian right, later Alexander’s governor of Babylon.

Consequences

Gaugamela opened the heart of the empire. Mazaeus surrendered Babylon, and Alexander entered the city in triumph in October 331 BC, confirming Mazaeus as governor. A Babylonian astronomical diary tablet, now in the British Museum, records the eclipse, the panic in Darius’s army and Alexander’s arrival, a rare contemporary non-Greek source for the period.

Susa surrendered in December with vast treasure. In early 330 BC Alexander forced the Persian Gates and reached Persepolis, whose palaces were burned a few months later. Darius tried to raise another army in the east, but in July 330 BC he was arrested and killed by Bessus and other nobles. Alexander gave him a royal burial and pursued his murderers as the avenger of the legitimate king.

Alexander now began to rule as a Persian king as well as a Macedonian one. He kept many Persian governors in office, adopted elements of Persian royal dress and court ceremony, and enrolled Iranian troops in his army, policies that later caused deep resentment among his Macedonian officers.

Legacy

Plutarch says Alexander was proclaimed king of Asia after the battle. Gaugamela is regarded as one of the most decisive battles in history, ending an empire that had ruled from the Aegean to the Indus for over two centuries.

Military historians study it as a model of how a smaller, disciplined army can defeat a larger one by forcing gaps in the enemy line and striking at the point of command. In art it was often called the Battle of Arbela, and Charles Le Brun painted it for Louis XIV in his series on the history of Alexander.

Timeline

• 333 BC, November: Alexander defeats Darius at Issus.
• 331 BC, spring: Alexander leaves Egypt and marches inland.
• 331 BC, summer: The Macedonian army crosses the Euphrates at Thapsacus.
• 331 BC, September: Alexander crosses the Tigris.
• 331 BC, 20-21 September: Total lunar eclipse.
• 331 BC, 1 October: Battle of Gaugamela.
• 331 BC, October: Alexander enters Babylon.
• 330 BC, July: Darius III is killed by Bessus.

Why it matters

Gaugamela ended the Achaemenid Persian Empire as a ruling power and handed its lands, treasures and royal cities to Alexander. It began the era in which Greek-speaking dynasties ruled from Egypt to Central Asia, reshaping the culture of the Middle East for centuries.