The Battle of Issus
- Davit Grigoryan
- Mar 10
- 6 min read
Updated: Mar 15
The Battle of Issus took place in November 333 BCE between the forces of Alexander the Great and the army of Darius III, king of the Achaemenid Empire. The battle occurred near Issus in Cilicia, located in Asia Minor. After the Battle of the Granicus in May 334 BCE, Alexander the Great took control of the western part of Asia Minor. Darius III, having gathered a large army, marched against him.
Background of The Battle
In 334 BCE, Alexander, the 21-year-old king of Macedonia, led a coalition of Greek forces against the greatest power of the time—the Persian Empire. He commanded an army of seasoned veterans, primarily the Macedonian phalanx armed with 18-foot sarissas and his elite cavalry companions. Together, in the battle at the Granicus, they achieved their first decisive victory over the Persian army. Now, as Alexander approached Sardis, the capital of the Persian province of Lydia, its commander surrendered without a fight.
But before Alexander could advance further, he needed to neutralize the Persian naval power. Persia had a powerful fleet with large naval bases in the eastern Mediterranean, which could cut off his communication lines with Greece. Instead of challenging the Persians at sea, Alexander decided to attack their nearest bases: the Greek coastal cities of Miletus and Halicarnassus. Both cities put up strong resistance, but by winter, they were taken.
The following spring, in 333 BCE, Alexander continued his advance into Lycia and Phrygia. In Gordium, he was shown the legendary "Gordian Knot". According to prophecy, whoever could untie it would rule all of Asia. Alexander simply took his sword and cut it in half. Meanwhile, Memnon of Rhodes, an experienced Greek general in Persian service, led the Persian warships into the Aegean Sea and captured the islands of Chios and Lesbos. However, following Memnon's sudden death from illness, the campaign was halted.
Eighteen months had passed since Alexander’s army crossed the Hellespont and invaded the Persian Empire. Now Alexander led his forces into Cilicia and was soon ready to cross the Nur Mountains into Syria. However, the main Persian army, led by King Darius III himself, moved north after the Greek army. Darius was determined to trap and destroy Alexander's army. Thus, he blocked Alexander's only retreat route by positioning his army on the coastal plain near Issus, which was only 2.5 kilometers wide from the mountains to the sea.
Disposition of the Troops
The armies met on the shore of the Issyk Bay in the valley of the small river Pinar. To the east, the Aman Mountains rose above the valley, making the coastal strip where the battle was only two and a half kilometers wide.
Darius, who arrived on the battlefield first, had the opportunity to take defensive positions on the left bank of the Pinar. Ancient sources, when estimating the size of his army, cited figures ranging from 400,000 to 600,000 men, which is an exaggeration intended to depict the Battle of Issus as a confrontation between a handful of Macedonians and countless hordes of barbarians. However, we lack other unbiased sources, so the actual size of Darius's army can only be estimated at approximately.
The core of the infantry was made up of Greek mercenary units, totaling about 10,000 to 12,000 men. In addition, Darius brought to the battlefield his elite unit, the Immortals, which numbered around 10,000 men. On his right flank, along the coast, Darius positioned cavalry units numbering between 10,000 and 15,000 horsemen. The remaining space was occupied by light infantrymen fighting in the traditional Persian style. In total, Darius's army might have numbered around 120,000 men at that time, but this estimate is highly tentative.
Darius was positioned at the center of the Persian lines on a royal battle chariot. Taking a central position in battle was quite typical for Persian rulers, as it allowed them to conveniently command the numerous units to their right and left.
Ancient authors do not specify the size of the Macedonian forces at the Battle of Issus. It can be assumed that due to numerous skirmishes, illnesses, and the need to allocate garrisons to maintain order in the conquered territories, Alexander had around 30,000 men available, which was fewer than during the crossing of the Hellespont. However, the colossal numerical superiority of the enemy did not unsettle Alexander. He understood that on the narrow coastal strip, Persia would not be able to deploy even half of its forces simultaneously.
In Alexander's advancing army, all the units located on the left side of the phalanx center were under the command of Parmenion. On the right wing, the archery units and lightly armed Agrianians were sent to drive the enemy from the foothills. They reached their goal fairly easily, and Darius's infantry quickly scattered in search of safety, retreating further into the mountains where they no longer posed a threat.
At the last moment, Alexander made tactical adjustments in his ranks. He sent two squadrons of Hetairoi, stationed in the center, to reinforce the right wing. At the same time, the Macedonian king, understanding the danger of a breakthrough by the Persian cavalry on his left flank, sent the Thessalian cavalry, originally stationed on the right wing, to assist Parmenion. Alexander carried out both of the final maneuvers unnoticed. The Thessalians and Hetairoi moved to the rear of the advancing phalanx, where they were concealed from the enemy by the Sarrus forest.
The Battle of Issus
Alexander continued to advance gradually, ensuring that his troops maintained a straight front. But when the Macedonian army was within bowshot of the enemy, he suddenly led a rapid attack. The units on the right wing, personally leading the Hypaspists, charged across the river and fell upon the enemy directly in front of them.
Unable to withstand Alexander’s assault, the Persian left wing was soon broken through. However, caught up in the attack, the leading units of the Macedonian cavalry became detached from the phalanx behind them. The uneven terrain and steep riverbanks made it extremely difficult for the phalanx soldiers to maintain their formation. Coordinating with other parts of Alexander’s army was out of the question.
On the opposite bank, the Macedonian phalanx was met by the disciplined ranks of Greek mercenaries and the Immortals, already prepared to withstand the assault. Advancing on the Macedonians, Darius’s infantry soon engaged in a fierce battle with Alexander's main forces, exploiting the irregularities in the Macedonian phalanx caused by the river crossing. The Greeks and Persians attempted to drive the Macedonians back into the river, and although they didn't succeed, the mercenary units began to encircle the Macedonians on the right flank of their formation. The phalanx soldiers suffered heavy losses but they didn't falter and continued to fight, struggling to fend off the advancing Greek mercenaries.
On the left flank of the Macedonians, commanded by Parmenion, the situation was even worse. There, by the riverbank and on the adjacent flat stretch of land, the Persians' overwhelming superiority in cavalry could turn into a decisive advantage. Without waiting for orders from Darius, the Persian cavalry charged across the river to attack the Thessalian cavalry, which was positioned directly opposite. An intense battle ensued, in which Parmenion's Thessalians barely managed to hold off the Persians.
The situation was saved by the cavalry units on the right flank, led by Alexander. Having driven the enemy into retreat on his flank, Alexander deployed his Hypaspists and charged into the ranks of the Greek mercenaries, disrupting their cohesion and forcing the Greeks to either retreat from the river or die on the spot.
After this, the Macedonian phalanx could resume its advance, destroying those who survived Alexander's cavalry's attacks. Alexander himself attempted to break through to Darius III. The battle around the Persian king was particularly fierce; many of his close attendants were killed, and the King of Kings hastily left the battlefield with great difficulty, switching to another chariot.
The collapse of the center and left flank of the Persian army triggered a general panic and the flight of all of Darius's forces from the battlefield. Many fleeing troops, especially the Greek mercenaries and Persian cavalry with heavy equipment, either failed to escape from the faster enemy or abandoned their weapons and found themselves defenseless against the pursuers.
Ancient sources report that a hundred thousand Persian infantry were killed or captured at Issus, while cavalry losses are estimated at 10,000 men. These figures seem excessively high and should also be seen as an attempt by ancient historians to exaggerate Alexander's achievements. At the same time, Alexander’s losses are reported as 300 infantry and 150 cavalry, though the intense fighting with Greek mercenaries in the center raises doubts about such minimal losses.
After the victory at Issus, the Macedonian forces soon occupied the Persian camp, where they discovered and captured the mother, wife, and children of Darius. Alexander treated the women of the royal family with chivalry and assured them that Darius had survived and that he held no grudge against him, as he was fighting solely for political purposes, namely, for the control of Asia. As for the money of the defeated king, it went to the victor. The Greek historian Arrian mentions the sum as 3,000 talents. This wealth was undoubtedly sufficient for procuring supplies and paying mercenaries for the upcoming campaign.
Alexander planned to continue his conquests southward. The next step was to subdue the trading hub of the Mediterranean — Phoenicia.
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