Battles & Wars › Greece, Rome & Han › Conquests of Alexander the Great
Battle of Gaugamela
October 1, 331 BC· Battle· Middle East & Africa
Well documentedSolid records, physical evidence or scientific consensus.
Alexander's decisive victory over Darius III on an open plain in northern Iraq, which effectively ended the Persian Empire.
See it on the Battles & Wars map →What happened
Darius chose flat ground near today's Mosul, leveled it for scythed chariots, and gathered an army far larger than Alexander's roughly 47,000. Alexander advanced at an angle, drawing Persian cavalry outward until a gap opened in Darius' line. He drove his Companion cavalry into the gap toward Darius, who fled again, while the phalanx and rear lines held. Babylon, Susa and Persepolis then fell to Alexander.
Why it matters
It ended the Achaemenid Empire as a fighting power and made Alexander lord of Asia: a textbook case of a commander exploiting one gap.
How we know
Arrian's and Curtius' accounts, and a Babylonian astronomical diary that records the lunar eclipse eleven days before the battle and the Persian army's rout.
Still debated
Darius' army size (ancient writers claim up to a million; modern estimates run roughly 50,000–120,000) and the battlefield's exact location are debated.
Connections (3)
▸Battle of Issus set up the decisive clash at Battle of GaugamelaWell documented
The connection
Beaten at Issus, Darius fled east and offered Alexander land and a ransom for his family. Alexander refused. While Alexander took Tyre and Egypt, Darius rebuilt a bigger army and chose open, flat ground at Gaugamela, where his numbers, cavalry and scythed chariots could work, unlike at Issus.
When and how
From Issus, southeastern Turkey, November 333 BC, to Gaugamela, northern Iraq, October 331 BC.
How we know
Arrian, Curtius and Diodorus record Darius' peace offers, the two-year gap and his choice of battlefield.
Debates and open questions
The exact terms of Darius' offers, and whether Alexander's refusal was as dramatic as later writers tell it, are uncertain.
▸Battle of Gaugamela sealed the fall of Achaemenid Persian EmpireWell documented
The connection
Gaugamela was Persia's last chance to field a royal army able to stop Alexander. After the defeat, Babylon and Susa opened their gates and Persepolis fell. Darius fled into Iran and was killed by his own officer Bessus in 330 BC, ending the Achaemenid dynasty.
When and how
Gaugamela, near Mosul, Iraq, October 1, 331 BC; Darius was killed in northern Iran in July 330 BC.
How we know
Greek histories, and a Babylonian astronomical diary describing the battle, the Persian army's flight and Alexander's approach to Babylon.
Debates and open questions
Whether Darius could have kept fighting from eastern Iran, and why his commanders turned on him, are debated.
▸Alexander the Great won his greatest victory at the Battle of GaugamelaWell documented
The connection
Darius III chose a flat plain where his much larger army and scythed chariots could deploy. Alexander angled his line to the right, stretching the Persian line until a gap opened, then led his Companion cavalry through it toward Darius, who fled. Persian resistance collapsed.
When and how
Gaugamela, near Mosul in northern Iraq, October 1, 331 BC.
How we know
Arrian and other ancient historians describe the battle; a Babylonian astronomical diary records Darius's defeat and helps fix the date.
Debates and open questions
Persian army size is unknown: ancient claims of up to a million are impossible, and modern estimates run from about 50,000 to 120,000.