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The Last Great War of Antiquity

The Byzantine and the Sassanid Empire were the two great powers of the Middle East and Western Asia for most of the last centuries of antiquity and the early Medieval period. During the third century, the Romans and the Sassanids fought fierce campaigns against one another, which saw the Roman sack the capital of the Sassanid Empire in the last 3rd century, while the Sassanids ravaged the eastern provinces of the Romans during the reigns of Ardhashir and especially his son Shapur.

Large scale warfare was abandoned during the early 4th century, but in the middle decades of the 4th century, during the reign of Shapur II, the two empires were once again at each other's throats, and even a Roman emperor, Julian the Apostate, was killed in the fighting.

After the death of Shapur, a measure of peace was once again re-established. The two empires co-existed largely at peace during the 5th century.

Things drastically changed in the 6th century. The largely peaceful 5th century saw limited fighting between the two superpowers, and the 6th century saw the return of warfare. During the reign of Emperor Justinian and his followers, decades of war erupted on the Byzantine-Sassanid border, which was only ended in 590, after Shah Hormizd and his successor Khosrow were overthrown.

Hormizd was killed, but Khosrow fled to Constantinople and asked Emperor Maurice for help. In exchange for soldiers who would restore him to this throne, Khosrow offered the transfer territories to the Romans.

The two agreed, and Maurice gave his support to Khosrow. The united power of Maurice and Khosrow loyalist nobles was enough to overwhelm the forces of the rebellious noblemen Bahram Chobin.

The grateful Khosrow honoured his agreement with emperor Maurice, and peace was restored after 590. The peace between the two empires allowed Maurice to transfer troops to the Balkans and reconquer lost territory from the Avars. If Khosrow had any thoughts of betraying Maurice, his fight against his uncle Vistham tied down his troops in any case, and he had no men to spare for an attack against Maurice.

The peace on the Byzantine-Sassanid frontier was maintained until 602, when the violent deposition of Maurice and his family gave Khosrow the perfect casus belli to attack the Byzantines.

The campaigns of emperor Maurice against the Avars were largely successful, however, the army of the Balkans was unruly and after coming close to mutiny a couple of occasions before, the commanders of the emperors lost control over the in late 602. The troops rebelled against Maurice and deposed the emperor. Maurice and all his sons were executed. The rebellious army named its commander Phocas as the new emperor, but the eastern provinces of the empire rebelled instead of accepting Phocas.

Rise of the Sassanids

The war begins and Persian ascendency

According to one version of the story, though not accepted by all historians, the eldest son of Maurice, Theodosius, fled to Khosrow, who began his war to restore Theodosius.

At first, they were assisted by the eastern provinces who were opposing the reign of Phocas. Shah Khosrow rejected all offers of peace from Phocas. The two empires were at war with one another throughout the reign of Phocas, and according to sources, the Persians had the better of the fighting. They were slowly, but surely conquering the border fortifications of the Byzantines.

In 608, the governor of Byzantine North Africa rebelled against Phocas. The governor named Heraclius, his son Heraclius the younger, and the cousin of Heraclius, Nicetas, became the key figures of this rebellion.

Nicetas was tasked with the capture of Egypt. It was a vital strategic objective for the rebels, as Egypt was the breadbasket of Constantinople. Whoever controlled Egypt controlled the grain shipments that kept the imperial city alive. It took Nicetas two years, but he ultimately defeated the subordinates of Phocas and secured Egypt for the Heraclian cause.

In the next phase of the rebellion, Heraclius the younger sailed to Constantinople, where he succeeded in overthrowing Phocas in a relatively bloodless manner. The betrayal of key nobles from Constantinople, including the commander of the imperial guard, the brother in law of Phocas, played a vital role here.

Once he secured the throne, Heraclius the younger tried to negotiate an end to the conflict between himself and Khosrow, however, the Persian Shah was having none of that, in his eyes, Heraclius was every bit as much a usurper as Phocas. Khosrow supported the claim of Theodosius, the real one if it was him or an impostor.

As peace with Khosrow was impossible, Heraclius prepared to continue the war. At first, he rid himself of the remaining Phocas loyalist in the army, who sabotaged his efforts to attack the Persians in the first few years of his reign. Once he was in control, he assembled a huge army and marched east to meet the Persians.

The two armies clashed at the Battle of Antioch in 613. Heraclius suffered a devastating defeat that cut his empire in half. For the next decade, the Persian onslaught was unstoppable, and the armies of Khosrow overrun Syria, Palestina and even Egypt.

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For each question, choose the best answer. The answer key is below.

  1. The Eastern and Western Roman Empires were finally divided in 395?
    • 395
    • 610
    • 410

Answer Key

  1. 395

Byzantine counterattack

If the Persians conquering much of the Byzantine East was not bad enough on its own, the Avars and Slavs also overran most of the Balkans and devastated the Byzantine provinces down to Greece. The empire was on the brink of collapse, but emperor Heraclius was not a man to give up easily.

Using whatever funds he was able to gather, including property given to him by the Church, he assembled and armed a new army. Heraclius also turned into a student of military history and supposedly studied every military bookhe found, be it history, strategy, or tactics to improve his knowledge and skill.

How Heraclius managed to turn things around is not entirely sure, but by 622, he and his army was ready. Heraclius knew that he lacked the manpower to attempt a reconquest of all his lost provinces, so he decided to force peace out of Khosrow by devastating the Persian heartland.

In the next 5 years, Heraclius campaigned in Armenia, modern-day Azerbaijan, Turkey and Iraq. He defeated Khosrow himself and the subordinates of Khosrow at nearly every battle they fought and devastated the Persian provinces in the process. Khosrow ordered a direct attack on Constantinople to take the wind out of the sails of Heraclius, but his offensive failed. Thanks to the Byzantine naval superiority, the Persians were unable to cross into Europe to assist their Avar and Slavic allies, who subsequently failed to overwhelm the defenders of Constantinople.

Worse than that, an angered Khosrow ordered the execution of the army's general, his brother in law, Sharbaraz. The Byzantines intercepted the message, and showed it to Sharbaraz, who decided to abandon Khosrow. Sharbaraz forged a letter to make his entire army abandon the Shah, according to the forged letter, Khosrow ordered the execution of most of the senior officers of the army.

Heraclius enlisted the alliance of the Western Turks for the next year and the combined Byzantine and Turkic army once again devestated Persia in the next year. In a surprise move Heraclius continued the campaign in late Autumn/Early Winter. He marched into Mesopotamia and defeated a Persian army in December at the Battle of Nineveh. His victory allowed him to threatan the Sassanid Captial Ctesiphon. The threat lead to a palace coup which overthrew Khosrow in late February.


The successor of Khosrow, Quabad finally agreed to make peace with Heraclius. According to the peace treaty the Persians evacuated all their conquered territories and the pre-war 602 status quo was reestablished.

Not long after the war a plague broke out in 628 which killed half the population of Mesopotamia. Shah Qubad was mong the dead and his death plunged the Sassanid Empire into a deadly civil war which laster for 4 years, when more than a dozen man and women claimed the throne for themselves.


For each question, choose the best answer. The answer key is below.

  1. The Sassanid Empire collapsed in the middle of the 7th century?
    • No
    • Yes

Answer Key

  1. Yes


Heraclius Emperor of Byzantium by Walter E. Kaegi

Byzantine military unrest by Walter Kaegi

Pourshariati, Parvaneh. (2017). Decline and Fall of the Sasanian Empire: The Sasanian-Parthian Confederacy and the Arab Conquest of Iran

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Andrew Szekler

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