By November of 333 Alexander reached the coastal city of Issus, located east of modern-day Adana and northwest of Aleppo. He knew Persian King Darius III was leading a large army to this region. Darius planned to link up with the Persian Mediterranean fleet and cut Alexander’s supply lines.

A large number of Alexander’s men became sick at this time. Alexander left them in Issus and marched into Syria, searching for Darius. The Persians outflanked Alexander and took Issus, massacring the Macedonian contingent there.

As Alexander hurried back to Issus, Darius took up positions north of the dry bed of the Pinarus River. To the East, on Darius’ left flank, rose the Amanus Mountains. To the West, Darius anchored his right flank on the Mediterranean (Gulf of Issus). Except for the even ground near the coast, the 1.5 mile long battle line stood in uneven brush-covered terrain favorable to defensive operations.

The Persian force outnumbered the Macedonians by more than two-to-one. Darius had 11,000 heavy cavalry, 20,000-29,000 heavy infantry (many of them Greek mercenary Hoplites), and 63,000 light infantry. Alexander fielded 5,850-7,050 cavalry, 22,000 Hoplites, and 13,000-14,000 Peltast light infantry.

Darius placed his cavalry on his right flank. He placed the Hoplite phalanx in the center and the Persian infantry phalanx on the left of his line. Darius then sent light infantry into the Mountains to outflank Alexander’s line.

Alexander kept his elite Macedonian cavalry force on his own right or eastern wing. He deployed a smaller contingent of Greek cavalry and some light forces on the left, facing Darius’ horsemen. He placed his heavy Macedonian infantry phalanx in the center.

The battle opened when Alexander sent part of his light force into the mountains to counter the Persian flanking attempt. The Macedonian skirmishers pushed the Persians back.

His flank secure, Alexander advanced his main force. The cavalry and the right wing of the phalanx managed to cross the riverbed and engage the Persian phalanx.

A Macedonian cavalry charge broke through the Persian phalanx, splitting Darius’ heavy infantry. The Macedonian skirmishers who had secured the mountains fell upon the isolated Persian left wing.

Alexander, wounded in the thigh by an arrow, led his heavy cavalry in a direct assault on Darius’ personal guard. The bloodiest part of the battle ensued, with the Macedonian’s relentlessly pressing to reach the chariot carrying Darius himself. Panicking, the Persian king fled the battlefield.

Meanwhile, on the western edge of the battlefield, the Persian heavy cavalry had crossed the Pinarus, pushing back the Macedonian cavalry on Alexander’s left flank. Alexander dispatched his reserve of Peltasts. With slings and javelins they checked the Persian cavalry’s advance.

As word of Darius’ flight spreads, the left and right wings of the Persian line collapsed into wild retreat. The elite phalanx at the Persian line’s center went down fighting, caught between the Macedonian phalanx in front and Alexander’s cavalry in the rear.

Alexander resisted the temptation to pursue Darius and march on the Persian capital. Thinking strategically, he consolidated his gains and secured his supply lines. Only then did he systematically continue his planned campaign to conquer the entire Persian empire.