Battle of the Persian Gate: An Achaemenid Thermopylae, 330 BCE

With the defeat of the Achaemenid armies at the Granicus (334 BCE), Issus (333 BCE), and Gaugamela (331 BCE) the road to the Persian heartland lay open. There was no Achaemenid army that could be brought to oppose Alexander and his Macedonians. The rich capitals of the Achaemenid Empire lay exposed to a foreign invader for the first time. Yet, there were those who were still determined to resist.

Ariobarzanes, satrap of Persis, was not willing to allow Alexander to advance without a fight. Gathering a small but determined band of followers, he marched out to give battle at the Persian Gate. Though heavily outnumbered, the Achaemenids had the advantage of the terrain, as the Macedonians had to pass through the rugged Zagros Mountains. The stage was set for an Achaemenid Thermopylae.

Alexander the Great had dealt the Achaemenid Empire a series of devastating defeats at the Granicus (334 BCE), Issus (333 BCE), and Gaugamela (331 BCE). He had also captured vast swathes of territory, including some of the empire’s greatest cities. Yet, this amounted to no more than around half of the empire, and the Achaemenid heartland remained untouched.

This meant that the Achaemenid king, Darius III, still had incredible resources that he could muster in defense of the empire. Moreover, the sheer size of the empire made it difficult for Alexander to mount an effective pursuit. A single defeat would potentially strand the invaders, hundreds if not thousands of miles away from safety. So, despite Alexander’s crushing string of victories, the Achaemenids were still more than capable of fighting.

The challenge for the Achaemenids was gathering resources from across their vast empire and concentrating them in a single place. Meanwhile, Alexander showed no signs of halting his advance. This continued pressure made it difficult for the Achaemenids to organize an effective resistance.

Darius III was now in Ecbatana, attempting to gather a new army after the disastrous defeat at the battle of Gaugamela in late 331 BCE. Having crossed the Zagros Mountains, he had hoped that they would form a barrier that Alexander would not attempt to cross until the spring. However, Alexander was not one to rest easy while an enemy stood against him. Having entered Babylon after defeating Darius at Gaugamela, Alexander was soon on the march with his army once more.

Alexander’s march from Babylon took him first to the great city of Susa, in the region of Elam. This was an ancient city, with a history dating back to as early as 4,395 BCE. It is mentioned throughout the Old Testament, mainly in the books of the prophets, but also in the book of Esther.

Cyrus the Great (r.550-530 BCE), founder of the Achaemenid Empire captured it around 540-539 BCE, and under his son Cambyses II (r.530-522 BCE) it became one of the four capitals of the empire. Darius the Great (r.522-486 BCE) then initiated a building program to make Susa a city worthy of the Achaemenids. Even the Greeks were not unfamiliar with the city; the playwright Aeschylus (c.525-456 BCE) used the city as the setting of his play The Persians. Yet for all its importance, Susa fell to Alexander with barely any resistance.

The capture of Susa was a devastating blow to the power and prestige of the Achaemenids as well as their morale. However, it was also a great strategic prize for Alexander. By capturing Susa, Alexander effectively bypassed Darius at Ecbatana, by threatening the heart of the empire. Due to its importance, Susa was connected to the rest of the Achaemenid Empire by a Royal Road.

The Royal Road was built centuries earlier by Darius I to facilitate communication throughout the empire. Alexander now had access to the perfect avenue for a march across the Zagros Mountains into the heart of the Achaemenid Empire. For the already well-traveled Macedonians, the Achaemenid capitals of Persepolis and Pasargadae were now within easy striking distance.

With Darius III attempting to raise a new army at Ecbatana, the defense of the Achaemenid heartland fell to a man named Ariobarzanes. The little that is known about Ariobarzanes paints an intriguing picture. He was a man of high stature as he was the satrap of Persis, the ancient Persian homeland. Prior to the reign of Darius III, the satrap of Persis does not appear to have been a position that existed. So, we get some sense of how critical the situation was for the Achaemenids. As for Ariobarzanes himself, it is known that he was an Achaemenid prince who fought at the battle of Gaugamela in 331 BCE. Darius III’s rule was never particularly secure, so he must have felt that Ariobarzanes was someone that he could trust and depend on.

The forces that Ariobarzanes had at his disposal were meager, considering what the Achaemenid Empire was capable of. Ancient Hellenistic sources report a (clearly inflated) army of 40,000 infantry and 700 cavalry. Modern estimates place his forces at 700-2,000. This more likely number probably means that he only had his personal guard and local militia to rely on. Nonetheless, Ariobarzanes was undeterred. He planned to make a stand at the so-called Persian Gates, a narrow pass through the Zagros Mountains through which Alexander would have to travel. It was the perfect spot for an ambush.

Guarding the Persian Gates

While Ariobarzanes was making his preparations, Alexander was forced to contend with the Uxian people. This semi-nomadic non-Iranian tribe lived in the Zagros Mountains and nearby plains and made regular raids on local settlements. Previous Achaemenid kings had granted them the privilege of collecting tolls from passing armies.

While many Greek writers interpreted this as a sign of Achaemenid weakness, it was more likely a deliberate policy. This was probably a gift-giving tradition that the Achaemenids used to condense tribes into confederations with rulers loyal to and dependent on the Achaemenids. When Alexander approached, the Uxians living on the plains surrendered while those in the mountains demanded their toll. Alexander, however, had other ideas.

Informing the Uxians that he would pay their toll on the day his army marched by on the main road, Alexander advanced with a picked force. Believing that Alexander would use the main road, the Uxians positioned their forces to keep watch on this route. However, using local guides, Alexander bypassed the Uxians by using alternate routes.

Alexander first positioned a force under his general Craterus (c.370-321 BCE) to cut off the Uxians’ escape route. Then, he stormed into their village and massacred all who resisted. Having secured the Uxian village, Alexander turned his attention to the Uxians guarding the main road and attacked them from the rear, again massacring those who resisted. The surviving Uxians surrendered and agreed to pay Alexander a yearly tribute in livestock.

With the Uxians subdued Alexander marched his army into the Persian Gate. As he was expecting no further resistance, he neglected to send out scouts. The overconfident Alexander marched his army right into Ariobarzanes’ ambush. Ariobarzanes had chosen his spot well; it was a narrow point, only a few meters wide, where the road curved and was overlooked by some high ground.

When the Macedonians marched into the trap the Achaemenids rained down boulders and arrows on them. The Macedonians attempted to retreat but were hampered by the narrowness of the road and the friendly units to the rear. Thus, the Achaemenids were able to inflict heavy casualties on the Macedonians, who were forced to abandon their dead and wounded. For the Greeks and Macedonians, leaving their dead companions behind without a proper burial was a great disgrace.

For Ariobarzanes, the ambush was a great success. His small force had inflicted heavy casualties on the enemy and forced them to withdraw. By stopping Alexander here at the Persian Gate, he prevented them from ravishing the Achaemenid heartland and demonstrated that they could be beaten. Most importantly, he bought more time for Darius III to rebuild the Achaemenid army.

Any other pass that the Macedonians attempted to take through the Zagros Mountains would require far more time and would require them to march greater distances. Yet Alexander neither retreated to take a different route nor launched another frontal attack. Instead, the two armies settled in for a month-long standoff in which neither had the strength to effectively attack the other.

It is not exactly clear how Alexander figured out a way around the stalemate. Yet regardless, he was able to find a way through the mountains that allowed him to get around behind the Achaemenid position.

While a token force under Craterus remained behind to guard the camp, Alexander, and Ptolemy (c.305-282 BCE), one of his generals, led an elite force in a pincer attack on the Achaemenids. Taken by surprise, the Achaemenids were attacked from above and behind by the Macedonians. Outnumbered and now surrounded, Ariobarzanes and his men fought back ferociously. There is some evidence to suggest that this battle cost Alexander the greatest amount of casualties in his campaign to conquer the Achaemenid Empire. The lack of precise casualty figures helps lend credence to this claim.

There are various accounts as to how Ariobarzanes met his end in the battle. In one version he was forced to surrender and was then most likely put to death in revenge for all the trouble he caused Alexander. Another version states that Ariobarzanes and his closest companions launched a final desperate suicidal charge against the Macedonians and were all slain. Finally, one version has Ariobarzanes and a portion of his army successfully breaking out of the encirclement and making their way back to Persepolis. Here, the commander of the city denied them entrance on the grounds that further resistance against Alexander was pointless. Ariobarzanes and his men were then either massacred under the city walls or marched back into battle and were slain.

In both ancient and modern times, the parallels between the battles of Thermopylae and the Persian Gates have been readily apparent. Alexander’s propaganda stated that his invasion was to avenge the earlier Achaemenid invasion in the 5th century. This was played up when Alexander finally made it to Persepolis.

The great city was given over to the Macedonian soldiers to loot and destroy, while the population was massacred and enslaved. For himself, Alexander took the royal treasury. This was probably one of the greatest concentrations of wealth in the entire world at the time. It also gave him complete financial freedom from the Greek city-states, who had helped finance the campaign.

Before leaving in search of Darius III, Alexander ordered the complete destruction of the city. His reasons are unclear, but Persepolis never fully recovered, and by the 10th century CE it ceased to exist as a city.

The Battle of the Persian Gate marked something of a turning point in Alexander’s campaign. From this point on the fighting would only get more difficult and more brutal. In part, this may have been because Alexander had accomplished his stated goal of punishing the Achaemenids for their earlier invasions. He needed a reason to continue, which he found in the form of Darius III.

However, the destruction of Persepolis following the Battle of the Persian Gate further eroded Darius III’s position. His support was dwindling, and the Achaemenid nobility felt that the time had come for new leadership if the empire was to survive.