Alexander the Great’s invasion of the Persian Empire was one of the most bold and ultimately decisive in history. Less than a decade after leaving Europe he had toppled history’s first great superpower and established a colossal empire of his own.
It all began with a battle on the Granicus River in modern-day Turkey, as his famous army faced its first major test against the Persians and their Greek auxiliaries.
An animated map showing the rise and fall of the Achaemenid Empire. Credit: Ali Zifan / Commons.
King Alexander III of Macedon
At the time of the battle of the Granicus Alexander was just twenty-two years old, but he was already a seasoned warrior. When his father Philip had come from the Macedonian north to conquer and subdue the Greek cities, Alexander had commanded his cavalry at the age of just sixteen, and he had been present when his father had declared an interest in attacking the Persians, who had been menacing the Greeks from across the Aegean for almost 200 years.
When Philip was assassinated in 336, his son was proclaimed King of Macedon, and decided to put his father’s dreams into action. Having learned war from his father and statecraft from the philosopher Aristotle, Alexander was already an impressive-enough figure for his new subjects to take this insane plan seriously, even though it was coming from a man barely out of his teens.
First, however, he had to keep hold of his European empire. With this boy-King now on the throne, Macedon’s dominions began to sense weakness, and Alexander had to put down revolts in the Balkans before doubling back and crushing Thebes, one of the old Greek cities.
After its defeat Thebes was razed and its old lands were divided between other nearby cities. The message was clear: the son was even more ruthless and formidable than the father.
Watch NowThe invasion begins
The following year – 334 BC – Alexander brought an army of 37,000 men across the Hellespont and into Asia. His father had combined the armies of Macedon with those of the Greeks, forming what historians call the “Corinthian League” in a conscious throwback to the League lead by Sparta and Athens that had defeated the Persians at Marathon and Salamis.
As soon as he landed in Asia, Alexander thrust his spear into the ground and claimed the land as his own – this would be no punitive expedition but a campaign of conquest. The Persian Empire was so vast that here – at its westernmost extremity – the task of defending it fell to the local satraps rather than their Emperor Darius in the east.
They were fully aware of Alexander’s arrival, and began to muster their own forces of tough Asian cavalry, as well as a large number of Greek Hoplite mercenaries who could match the Macedonian infantry.
Both fought in tight phalanxes of men armed with a long spear and keeping a rigid formation, and the Persians hoped that they would cancel each other out while their strong cavalry dealt the killer blow.
The impenetrable mass of the Macedonian phalanx – these men were the nucleus of Alexander’s army at the Granicus River and remained so for the rest of his conquests.
Memnon’s advice
Prior to the battle, Memnon of Rhodes, a Greek mercenary commander in Persian service, had advised the satraps avoid fighting a pitched battle against Alexander. Instead he suggested they employ a ‘slash and burn’ strategy: lay waste the land and let starvation and hunger tear away at Alexander’s army.
It was a smart tactic – Alexander’s food reserves were already running low. But the Persian satraps were damned if they were going to devastate their own lands – lands the Great King had entrusted to them. Besides, where was the glory in that?
They thus decided to dismiss Memnon’s advice and to face Alexander on the field of battle much to the young Macedonian king’s delight.
Listen NowThe Battle of the Granicus River
And so in May 334 BC the Persian and Macedonian armies faced each other on opposite sides of the Granicus River. The Persian army consisted predominantly of cavalry but it also had a substantial number of Greek mercenary infantry. In total it numbered nearly 40,000 men according to the Greek historian Arrian, slightly larger than Alexander’s 37,000-strong force.
Alexander’s experienced second-in-command Parmenion advocated attacking the next day, but his impetuous commander overrode him and decided to cross the river immediately, taking the Persians by surprise. His heavy phalanx was in the middle, while the cavalry protected the flanks – with the right taken by the King and his famous Companion Cavalry: Macedonia’s elite shock cavalry unit.
Battle commenced when Alexander mounted his horse and ordered the cavalry to cross the river, himself leading the Companions.
An intense cavalry fight followed:
…a tangled mass of horse against horse and man against man, as each side struggled to achieve its aim
Eventually Alexander and his cavalry, equipped with sturdy lances that were far more effective than the Persian spears, gained the upper hand. At the same time Alexander’s light infantry moved among the horses and created further panic in the Persian ranks.
A diagram of the Battle of the Granicus River.
Alexander’s dice with death
Alexander remained in the thickest of the action throughout the fight. Yet this very nearly cost him his life.
Midway through the battle, Alexander was set upon by two Persian satraps: Rhoesaces and Spitamenes. Rhoesaces struck Alexander on the head with his scimitar, but Alexander’s helmet bore the brunt of the blow and Alexander responded by thrusting his lance through Rhoesaces’ chest.
As Alexander was dealing this killer strike, Spitamenes appeared behind him and raised his scimitar to land the death blow. Fortunately for Alexander, however, Cleitus ‘the Black’, one of Alexander’s senior subordinates, sliced off Spitamenes’ raised arm, scimitar and all.
Cleitus the Black (seen here wielding an axe) saves Alexander’s life at the Granicus.
After Alexander recovered from his near-death experience, he brought his men and the Persian cavalry out to the left, where the latter were comprehensively defeated.
The Persian army collapses
The Persian cavalry’s demise left a hole in the centre of the Persian line which was quickly filled by the Macedonian phalanx, who engaged the enemy infantry and put the poorly-equipped Persians to flight before starting on the Greeks. Most of the Satraps had been killed in the cavalry duel with Alexander and their leaderless men panicked and left the Greeks to their fate.
Alexander’s victory at the Granicus was his first success against the Persians. According to Arrian, he lost just over a hundred men in the battle. The Persians, meanwhile, lost over a thousand of their cavalry, including many of their leaders.
As for the Greek mercenaries serving in the Persian army, Alexander labelled them traitors, had them surrounded and annihilated. The conquest of the Persian Empire had begun.
