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Alexander the Great‘s Crowning Victory: Why the Battle of Issus Was a Defining Moment

The Battle of Issus in 333 BC was a watershed moment in the young Alexander the Great‘s spectacular campaign to conquer the Persian Empire. This clash between the upstart Macedonian king and Darius III, the King of Kings, on the coastal plain of Issus would have far-reaching consequences. It represented the first time these two legendary leaders met in battle – a battle that Alexander won decisively against great odds through a combination of tactical brilliance, bold leadership, and the unshakable bravery of his men. The victory at Issus propelled Alexander to even greater heights and spelled the beginning of the end for Persian power in the Mediterranean.

The Road to Issus

Alexander‘s campaign against the Persian Empire began in 334 BC when he crossed the Hellespont with an army of approximately 40,000 men, consisting of 32,000 infantry and 5,100 cavalry (Arrian, 1971). After securing a foothold in Asia Minor with a hard-fought victory at the Battle of the Granicus, Alexander marched south along the Ionian coast, liberating Greek cities from Persian control.

However, Alexander‘s progress was slowed when he fell seriously ill after bathing in the icy waters of the Cydnus River near Tarsus in Cilicia (Plutarch, 1919). This delay gave Darius time to gather a massive army and march west to confront the Macedonian invader. Ancient sources give wildly inflated figures for the size of Darius‘s force, with Arrian (1971) citing over 500,000 men and Plutarch (1919) claiming 600,000. Modern historians generally estimate the Persian army at Issus numbered between 60,000-100,000 (Fuller, 1958; Green, 1991), giving them a significant numerical advantage over Alexander‘s troops.

Darius initially positioned his army on the Plain of Sochi in Syria, which was ideally suited for deploying his large force. However, as the weeks dragged on with no sign of Alexander due to his illness, Darius grew impatient. Against the advice of his Greek mercenary commander Charidemus, who warned him not to face the Macedonians on broken ground (Diodorus, 1989), Darius decided to surprise Alexander by marching through the Amanus Mountains to cut off his route south.

Alexander, who had by this time recovered and resumed his march, was stunned to learn that the Persians had emerged in his rear and slaughtered the Macedonian wounded and camp followers at Issus (Arrian, 1971). He quickly wheeled his army around and force-marched back to Issus to confront Darius. The stage was set for an epic showdown.

The Battlefield

The Battle of Issus was fought on a narrow coastal plain bordered by the Mediterranean Sea to the west and the Amanus Mountains to the east. The width of the battlefield was only about 2.5 km, hemmed in by the mountains and sea (Devine, 1985). This restricted space heavily favored the smaller and more compact Macedonian army.

Alexander arrayed his line with the Companion Cavalry on the right flank, the Thessalian cavalry on the left, and the Macedonian phalanx in the center, supported by hypaspists and Cretan archers (Arrian, 1971). The Persians had their Greek mercenaries facing the Macedonian phalanx, the Persian cavalry concentrated on their right wing, and masses of Iranian infantry on their left (Plutarch, 1919).

Macedonian Army Persian Army
Infantry 32,000 50,000-80,000 (est.)
Cavalry 5,100 10,000-20,000 (est.)
Commanders Alexander the Great Darius III
Key Units Companion Cavalry, Macedonian Phalanx, Thessalian Cavalry Greek Mercenaries, Persian Cavalry, Immortals

The Battle

Alexander opened the battle with characteristic aggression and speed. He personally led the Companion Cavalry in a charge across the Pinarus River directly at the masses of lightly-armed Persian infantry on the enemy‘s left flank (Arrian, 1971). The impact was devastating. The Persians, terrified by the ferocity and rapidity of the assault, fled in terror before the Companions could even close with them.

In the center, the Macedonian phalanx was hard-pressed by the Greek mercenaries in Darius‘s service. These were seasoned hoplites fighting in their traditional formation and they gave the Macedonians all they could handle (Plutarch, 1919). It was a close-run affair until the mercenaries saw their left flank crumble under Alexander‘s charge. They began to waver.

The critical action, however, was on Alexander‘s left, where the Thessalian cavalry was facing the cream of the Persian army – the feared Persian cavalry. In a fierce mounted battle, the Thessalians managed to hold their own against the more numerous Persians (Diodorus, 1989). Had they failed, the Persians could have swept behind the Macedonian line and wreaked havoc. The Thessalians‘ heroic stand was a deciding factor.

With the collapse of his left flank and his cavalry unable to break through, Darius saw the battle slipping away. In a shocking move, the King of Kings turned his chariot and fled the field (Arrian, 1971). Darius‘s flight utterly demoralized the Persians. Panic rippled through their ranks as men rushed to escape. The Macedonians, sensing victory, pressed their attack and cut down thousands of fleeing enemies. It was a crushing defeat for Darius. He left behind his mother, wife and children who were captured in his camp by the victorious Macedonians.

Aftermath and Legacy

The Battle of Issus had immense strategic ramifications. It gave Alexander control of the Eastern Mediterranean and effectively severed Persia‘s naval lifeline to its forces in the Aegean. As the historian Arrian (1971) wrote: "Darius‘s flight decided the battle in Alexander‘s favor and he became master of all the territory which had been subject to Darius."

Alexander followed up his victory by capturing Phoenicia, the base of Persian naval power, after a grueling 7-month siege of Tyre (Green, 1991). He then marched into Egypt, where he was welcomed as a liberator and crowned Pharaoh. In Egypt, Alexander founded the great city of Alexandria which would become a center of learning and culture for centuries to come.

But Alexander was not content to rest on his laurels. Issus was merely a stepping stone to his ultimate goal: the complete conquest of the Persian Empire. In 331 BC at the Battle of Gaugamela, Alexander would again face Darius, this time on a battlefield of the Persian king‘s choosing. Despite being outnumbered by as much as 5 to 1 (Fuller, 1958), Alexander would once more emerge triumphant, effectively toppling Darius from his throne. Issus had set the stage for Gaugamela, the battle that would reshape the ancient world.

From a military standpoint, Issus showcased Alexander‘s genius as a tactician and a leader. His bold, aggressive style and his ability to quickly seize opportunities as they presented themselves confounded his enemies. As the military historian J.F.C. Fuller (1958) noted, "At Issus Alexander showed that he had grasped what no other general had grasped before – the potentiality of the mounted arm when handled strategically, tactically and morally as a psychological weapon."

But Issus was more than just a display of innovative tactics. It also highlighted Alexander‘s leadership and the deep bond he forged with his men. Plutarch (1919) relates that when Alexander was offered water after the battle, he refused to drink until all of his men had quenched their thirst first. This type of selfless leadership inspired fanatical loyalty among his troops.

Historians from antiquity to the present day have recognized Issus‘s pivotal role in Alexander‘s career and its broader impact on history. The Roman historian Curtius (1946) called it "the first great victory" that established Alexander‘s reputation. Modern Alexander biographer Robin Lane Fox (1973) asserts that "the Macedonians‘ victory at Issus was the victory which opened the way to the rest of Asia."

In conclusion, the Battle of Issus in 333 BC was a turning point not just in Alexander the Great‘s unprecedented campaign of conquest, but in the history of the ancient world. This against-the-odds triumph over the Persians demonstrated Alexander‘s military genius, cemented his leadership, and paved the way for his eventual domination of the largest empire the world had yet seen. Issus was the key that unlocked the door to Alexander‘s destiny and his indelible imprint on history. Its significance can hardly be overstated.


Arrian. (1971). The Campaigns of Alexander. Translated by Aubrey de Sélincourt. Penguin Classics.

Curtius. (1946). History of Alexander. Translated by J. C. Rolfe. Loeb Classical Library.

Devine, A. M. (1985). The Battle of Issus: A Study in Ancient Tactical Thought. The Ancient World, 12, 25-37.

Diodorus. (1989). Diodorus of Sicily in Twelve Volumes. Translated by C. H. Oldfather. Loeb Classical Library.

Fox, R. L. (1973). Alexander the Great. Dial Press.

Fuller, J. F. C. (1958). The Generalship of Alexander the Great. Rutgers University Press.

Green, P. (1991). Alexander of Macedon, 356-323 B.C.: A Historical Biography. University of California Press.

Plutarch. (1919). The Parallel Lives. Loeb Classical Library Edition. Retrieved from*/home.html.