Alexander the Great’s Conquest of the Persian Empire

The Battle of the Granicus

'The Battle of the Granicus' (1665) by Charles Le Brun depicts Alexander the Great at the center of the cavalry battle. (Image: Public Domain)

Alexander the Great, also known as Alexander III or Alexander of Macedonia (356-323 BCE), overthrew the Persian empire, carried Macedonian arms to India, and laid the foundations for the Hellenistic world of territorial kingdoms.

Alexander the Great fought three major battles against the Persian Empire: the fight of Granicus, the battle of Issus, and the battle of Gaugamela. These decisive victories caused the Persian army to retire, giving Alexander the Great an additional opportunity to penetrate further into Persian territory.

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On November 5, 333 BCE, near the mouth of the Pinarus River, the Hellenic League, headed by Alexander the Great, defeated the army of the Achaemenid Empire, led by Darius III, in the second great battle of Alexander’s campaign against the Persians.

In this article, we’ll discuss the three significant battles of Alexander the Great that led to his Persian conquest. 

Alexander the Great at the battle of Granicus 

Granicus was the two powers’ first significant battle. It took place in 334 BCE on the Granicus River’s banks. Alexander the Great’s army numbered 40,000 soldiers, supplemented by forces already stationed in Asia. There are contradictions in the Persian army; Arrian estimates 20,000 cavalry and 20,000 Greek mercenaries, whereas only 4,000 – 5,000 Greek mercenaries were there.

Alexander the Great launched his offensive by striking the Persian left flank and drawing and weakening the Persian center. Then, given the opportunity, Alexander directed a frontal attack on his companion’s right flank, followed by his entire army. As Alexander’s forces proved too strong for the Persians, the Persian cavalry retired, leaving the Greek mercenaries vulnerable to attack.

The Persians’ Greek mercenaries surrendered, but Alexander the Great refused to talk and slaughtered them to punish traitors. As a result, 2,000 of the 5,000 Greek mercenaries were left behind and transported to harsh work camps in Macedonia.

Alexander the Great at the battle of Issus.
The Battle of Issus (1602) by Jan Brueghel the Elder. (Image: Public Domain)

The Battle of Issus 

Alexander the Great attacked Asia Minor after his victory in Granicus. Alexander tried to acquire coastal settlements to weaken the Persian Fleet, which was much superior to his naval. After discovering that Darius III, King of the Persian Empire, was in Sochi, Alexander captured Issus and marched south.

Darius marched north, recaptured Issus, and then followed Alexander’s path south. However, Darius’ march south was cut short near the Pinarus River, which had a small coastal plain, when spies detected Alexander’s army was approaching from the north.

When the Macedonian cavalry burst through the Persian left flank, it moved to help the infantry, leading Darius to depart the battlefield, producing instability among the remaining forces, who also fled. Nevertheless, this was a significant victory for the Macedonians, as no one had ever destroyed the strong Persian army while the king was there.

The Battle of Gaugamela
The Battle of Gaugamela (1650s) by Jacques Courtois. (Image: Public Domain)

The Battle of Gaugamela

The final battle between Alexander the Great’s and Darius’ forces occurred in the summer of 331 BCE at Gaugamela. Even though the Persian army was at its height, Alexander employed the same arrangement used at Issus due to the open flat terrain.

In anticipation of the Persian flanking move, the Macedonian cavalry on both wings was pushed inward, drawing the Persian cavalry away from the heavy infantry core. Darius concentrated his attention on the Macedonian right flank, moving his front soldiers there and reducing his ranks to his left.

Alexander promptly took advantage of the circumstance, bringing the following cavalry directly to the vulnerable spot. While Alexander was cutting through the weak spot, the Macedonians fought the Persian army. Instead of fighting back, Darius’ men rode into the Macedonian camp and were slaughtered by reserve forces in the army’s rear. Darius was forced to flee the battlefield once more after his center warriors were killed, preventing him from being apprehended.


Alexander the Great’s final fight gave him control of all of Achaemenid Persia. After three crushing defeats (327 BCE), Persian morale was shattered after three crushing losses, and Alexander wasted no time restoring it. He persuaded the rest of Persia to follow him to the exotic regions of the northeastern Indus valley.

Following the fight, the Hellenes seized Darius’ wife, Stateira I, his children, Stateira II and Drypetis, and Darius’ mother, Sisygambis, who had accompanied Darius on his journey. Alexander the Great, who subsequently married Stateira II, showed considerable regard for the captive ladies.

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