Battle of Issus in 333 BC was the first direct conflict of the Macedonian King Alexander the Great and Persian Great King Darius III. In the battle of Granicus, which took place one year before this battle, the Persian troops and Greek mercenaries in the service of the Persian satraps were defeated by Alexander.
Alexander proceeded along the western coast of Asia Minor to the Persian inland after the battle of Granicus. Alexander heard in Tarsus that Darius gathers a huge army. Alexander had to prevent the army of Darius to combine with the Persian fleet, which still operated in the Mediterranean Sea. If Darius combined with the fleet, Persians would not have problems with supplying and Darius could land in the rear of Alexander’s army as well.
Alexander sent Parmenion with 15,000 men ahead to occupy the mountain passes on the borders of Syria and Cilicia, before the Persian could reach them. Alexander waited with the main army in Tarsus and when Parmenion completed this task, Alexander set out with his army to Issus.
The Persian army moved forward from Babylon to Syria in November. Darius followed the northerly way, because he knew that Parmenion controlled the Syrian passes. He left the Syrian plains and marched towards Issus with his large army. He occupied Issus without resistance and let cut off hands of all ill and wounded soldiers Alexander left there. Darius found himself in the rear of the Macedonians and so he cut them off from their supply lines and set out to chase them immediately.
When Alexander realised that Darius was in the rear of him, he ordered the army to return immediately back to Issus. From a topographical point of view the battlefield was clamped by high mountains on one side and by the Mediterranean Sea on the other side. So the Persians could not fully take advantage of their superiority in numbers, which was very advantageous for Alexander.
Course of the battle of Issus
Alexander placed most of his cavalry on the right wing, where he also commanded the whole battle from. The core of the Macedonian group consisted of phalanx. Parmenion’s cavalry and infantry assumed the position on its left wing near to the sea.
Darius sent his heavy cavalry on the right side against Parmenion, because the local flat terrain was perfect for a cavalry attack. The centre of the Persian line was occupied by Greek mercenaries. Only lightly armed Persian infantry should traditionally operate on the left.
The battle was started by the Persian cavalry with crossing the river and attacking the Parmenion’s troops. Alexander together with the Macedonian heavy cavalry set out to meet the enemy to break through the Persian light infantry. It actually yielded under the attack, but it did not retreat and continued in fighting. Alexander gradually fought his way to Darius, who fled from the battle.
Alexander's phalanx crossed the wild mountain river Pinarus, but the formation was disrupted then. The Greeks in the service of Darius used this situation and gave them considerable losses. Also Parmenion’s situation was becoming serious. Persian cavalry pushed Alexander's Peloponnesian cavalry and his Greek allies there. Alexander sent his cavalry to help Parmenion, but Persian cavalry did not halt its movement till they saw the King’s escape. Alexander ordered to slaughter the fleeing enemy infantry.
Consequences of the Battle of Issus
Thanks to the victory at Issus Alexander seized the entire western half of the Persian Empire. His dream of dominating Asia began to approach its fulfilment. Darius III offered to leave him the control over the territory beyond the Halys River and eternal alliance between the two empires in exchange for release of his family members. Alexander refused his proposal without hesitation.