The fighting took place in Gaugamela, a village on the banks of the river Bumodus, north of Arbela (modern-day Erbil, in Iraqi Kurdistan).

Despite being heavily outnumbered, the Army of Macedon emerged victorious due to the employment of superior tactics and the clever usage of light infantry forces.

In November 333 BC, King Darius III had lost the Battle of Issus to Alexander the Great, which resulted in the subsequent capture of his wife, his mother and his two daughters, Stateira II and Drypetis.

[11][12] Alexander fought at the Siege of Tyre (332 BC), which lasted from January to July, and the victory resulted in his control of the Levant.

[14][15] Persian troop counts in Egypt were diminished due to many soldiers being removed to support the Battle of Issus and dying there.

[21] Diodorus Siculus (1st century Greek historian) likewise mentions the offer of all territory west of the Halys river, a treaty of friendship and a large ransom for Darius' captives.

Diodorus is the only ancient historian who mentions the fact that Alexander concealed this letter and presented his friends with a forged one that was favorable to his own interests.

He praised Alexander for the treatment of his mother Sisygambis, offered him all territory west of the Euphrates, co-rulership of the Achaemenid Empire, the hand of one of his daughters and 30,000 talents of silver.

Furthermore, Diodorus and Curtius Rufus mention that Mazaeus employed scorched-earth tactics in the countryside through which Alexander's army had to pass.

[40][41] Several researchers have criticized the Persians for their failure to harass Alexander's army and disrupt its long supply lines when it advanced through Mesopotamia.

[42] Classical scholar Peter Green thinks that Alexander's choice for the northern route caught the Persians off guard.

Darius would have expected him to take the faster southern route directly to Babylon, just as Cyrus the Younger had done in 401 BC before his defeat in the Battle of Cunaxa.

[43] Historian Jona Lendering, by contrast, argues that Darius intentionally led the Macedonians to Gaugamela, the Persians' preferred battlefield.

[1][32][46] Although there is general acceptance among modern scholars of Arrian's numbers for Alexander's forces, the opposite is true with respect to the ancient sources' reports on the size of Darius's army.

"[49] Similarly, Worthington writes that the figures given by Diodorus, Plutarch, and Curtius "are absurdly high numbers to show how hopelessly outnumbered Alexander's army was[.

]"[50] Reinhold Bichler's case study surveyed 20 different sources published between 1920 and 2014, showing that various authors have given widely divergent estimates of Darius's forces, with others remarking that it is not possible to reach any conclusion other than that Alexander's army was outnumbered by the Persians.

Darius had recruited the finest cavalry from his Eastern satrapies and from allied Scythian tribes[clarification needed] and deployed scythed chariots, for which he had ordered bushes and vegetation removed from the battlefield to maximize their effectiveness.

Mazaeus commanded the right flank with the Syrian, Median, Mesopotamian, Parthian, Sacian, Tapurian, Hyrcanian, Caucasian Albanian, Sacesinian, Cappadocian and Armenian cavalry.

The mercenary cavalry was divided into two groups, veterans on the flank of the right and the rest in front of the Agrianes and Greek archers, who were stationed next to the phalanx.

While the infantry battled the Persian troops in the centre, Alexander began to ride all the way to the edge of the right flank, accompanied by his Companion Cavalry.

His plan was to draw as much of the Persian cavalry as possible to the flanks, to create a gap within the enemy line where a decisive blow could then be struck at Darius in the centre.

However, by careful use of reserves and disciplined charges, the Greek troops were able to contain their Persian counterparts, which would be vital for the success of Alexander's decisive attack.

As told by Arrian: Then the Scythian cavalry rode along the line and came into conflict with the front men of Alexander's array, but he nevertheless still continued to march towards the right, and almost entirely got beyond the ground which had been cleared and levelled by the Persians.

But the rest of the Bactrians, drawing near to the Paeonians and Grecian auxiliaries, caused their own comrades who were already in flight to turn and renew the battle; and thus they brought about a general cavalry engagement, in which more of Alexander's men fell, not only being overwhelmed by the multitude of the barbarians, but also because the Scythians themselves and their horses were much more completely protected with armour for guarding their bodies.

[68]The tide finally turned in the Greek favor after the attack of Aretes' Prodromoi, likely their last reserve in this sector of the battlefield.

This large wedge then smashed into the weakened Persian center, taking out Darius' royal guard and the Greek mercenaries.

Darius was in danger of being cut off, and the widely held modern view is that he now broke and ran, with the rest of his army following him.

This is based on Arrian's account: For a short time there ensued a hand-to-hand fight; but when the Macedonian cavalry, commanded by Alexander himself, pressed on vigorously, thrusting themselves against the Persians and striking their faces with their spears, and when the Macedonian phalanx in dense array and bristling with long pikes had also made an attack upon them, all things together appeared full of terror to Darius, who had already long been in a state of fear, so that he was the first to turn and flee.

However, unlike on the left with Bessus, the Persians soon fell into disorder as the Thessalians and other cavalry units charged forward at their fleeing enemy.

As at Issus, substantial loot was gained, with 4,000 talents captured, the King's personal chariot and bow and the war elephants.