After the Hellenic League soundly defeated the Persian satraps of Asia Minor (led by Greek mercenary Memnon of Rhodes) at the Battle of the Granicus, Darius took personal command of his army.

He gathered reinforcements and proceeded to lead his men in a surprise march behind the Hellenic advance, in order to cut off their line of supply.

At that location, the distance from the Gulf of Issus to the surrounding mountains is only 2.6 km (2 mi), a place where Darius could not take advantage of his superiority in numbers.

He then proceeded to occupy most of Asia Minor, with the idea of capturing all coastal settlements so as to negate the power of the vastly superior Persian fleet.

If Darius were to reach the Gulf of Issus, he could use the support from the Persian fleet under Pharnabazus still operating in the Mediterranean Sea, thus easing his supply and possibly landing troops behind the enemy.

In November, Alexander received reports that the great Persian army had advanced into Syria to a town named Sochoi.

[citation needed] Darius' large army could not be supported in the field during winter and his cities in Phoenicia were already in unrest at the arrival of Alexander.

Darius instead moved north from Sochi and around the mountains, through the Amanic Gate or another nearby pass, emerging behind Alexander's position and on his supply and communication lines.

Next to the Greek phalanx Darius spread his Persian infantry, the Cardaces, along the river and into the foothills, where they wrapped around to the other bank and threatened Alexander's right flank (the formation resembled gamma, Γ).

In the left flank, the Thessalian struggled against the outnumbering mass of Persian heavy horse that faced them, delivering charges and retreating again to buy time.

Then the Hypaspists led by Alexander on foot delivered an assault on the Cardaces, and managed to punch a hole through the Persian line.

Alexander then mounted a horse at the head of his Companions and led a direct assault against Darius and his bodyguards, causing them to flee from the battlefield.

Arrian notes Ptolemy mentioning that while pursuing Darius, Alexander and his bodyguards came upon a ravine which they easily crossed on the piled up bodies of dead Persians.

Later, the Spartan king Agis III recruited the Greek mercenary survivors of the Battle of Issus who had served in the Persian army, a force of 8,000 veterans, and used them in his fight against the Macedonians.