The Byzantine Emperor who Declared Greek the Official Language

Heraclius (Ancient Greek: Ἡράκλειος) was emperor of the Byzantine Empire from 610 until his death in 641, during which Greek became the official language of the Byzantine state.

Life and rise to power

Heraclius’ father, Heraclius the Elder, was an Armenian exarch of Carthage and a seasoned general under Emperor Maurice, with a notable record of triumphs on the Persian front during the war of 572–591. His son, the future emperor Heraclius was skilled in the Greek language, despite his Armenian descent.

During the brutal reign of the usurper Emperor Phocas, who had overthrown Maurice in 602, and amidst a new Persian invasion of the Near East triggered by Phocas’ coup, the Persians for the first time extended their campaigns beyond border conflicts in Armenia and Mesopotamia, launching a massive invasion into the eastern Roman provinces.

In response to these crises, Heraclius the Elder initially cut off communication with the capital and halted the African grain supply to Constantinople. He eventually assembled a formidable Roman military force to confront Phocas. Under the command of his son Heraclius, a fleet sailed from Carthage in 609, while simultaneously, the army, led by his nephew Niketas, marched overland—both advancing toward Constantinople.

As Heraclius prepared for this campaign, the Patriarch of Carthage reportedly gave him a cryptic blessing. The patriarch declared, “God be with him,” implying divine favor for Heraclius’ mission. They interpreted this blessing as a prophecy of Heraclius’ eventual success, bolstering his resolve and rallying the support of his followers.

Carthage, as the seat of the Exarchate of Africa, played a vital role in Heraclius’ rebellion. It was one of the empire’s wealthiest provinces and a key stronghold against both internal unrest and external threats. After Heraclius ascended the throne, the Exarchate of Carthage continued to serve as a critical region for Byzantine defense, particularly against the advancing Arab Caliphate.

The overthrow of Phocas and early challenges

Heraclius eventually overthrew Phocas, the son of the Exarch of Africa. Despite having limited experience, Heraclius began the arduous task of restoring the state from Phocas’ destructive rule. However, despite his campaigns in Mesopotamia, Heraclius was unable to prevent the Persians from besieging Constantinople. The Persians launched their attack from Chalcedon on the Asian side of the Bosphorus.

From May 14 to 15, 626, riots broke out in Constantinople against John Seismos, who had proposed canceling the bread rations of the imperial guard school and raising the cost of bread to three-to-eight follis. Although they removed John from office, unrest persisted within the city.

Chosroes, seeking a decisive victory against the Byzantines, left Sahin with 50,000 men in Mesopotamia and Armenia to occupy the Byzantine army. With a smaller force, Chosroes encamped at the walls of Chalcedon. He had allied with the Avar Khagan to launch a coordinated attack on Constantinople from both the European and Asian sides. The Persian army encamped at Chalcedon, while the Avars and Slavs encamped on the European side, where they destroyed the Aqueduct of Valens.

Patriarch Sergius and the role of Greek in the defense of Constantinople

Despite the threats, Byzantine naval control of the Bosphorus prevented the Persians from sending troops to the European side to assist their allies. This limitation reduced the effectiveness of the siege, as the Persians were skilled in siege warfare. Communication between the Persians and the Avars was also hampered by the heavily guarded Bosphorus, although some coordination undoubtedly occurred.

The defense of Constantinople was led by Patriarch Sergius and the patricians. Patriarch Sergius I of Constantinople, like the emperor, was skilled in the Greek language. Greek was the liturgical language of the Eastern Orthodox Church. Sergius, as a prominent ecclesiastical leader, would have used it extensively in theological discourse, sermons, and official communications, like the emperor would also use Greek language for political reasons.

The siege of Constantinople: Defense and strategy

Heraclius divided his forces into three parts. Although he considered the city relatively secure, he requested reinforcements in Constantinople to bolster morale. One part of the army, under the command of his brother Theodore, was sent to confront Sahin. The third, smaller contingent remained under Heraclius’ direct command, tasked with launching raids into Persian territory.

On June 29, 626, a coordinated assault on the city walls began. Inside Constantinople, 12,000 well-trained Byzantine cavalry and infantry, aided by the city’s inhabitants, defended against approximately 80,000 Avars and Slavs. The Persians had reached Chalcedon before Phocas’ overthrow, but the Byzantine navy’s dominance hindered their siege effort.

Despite continuous assaults with siege engines over the course of a month, morale within the city remained high, thanks to Patriarch Sergius. Through fervent religious processions and the display of the icon of the Virgin Mary, Sergius inspired confidence in divine protection.

The attackers suffered devastating losses at sea. That’s because the sea destroyed the Avaroslavian fleet and the Persian fleet in two separate naval battles. This led the besiegers to abandon their efforts, apparently believing that divine intervention had secured the Byzantine victory.

Heraclius successfully defended Constantinople during the critical siege of 626 AD. The city faced simultaneous attacks from the Avars and Slavs in the west and the Persians in the east. The famous “Akathist Hymn” was composed in gratitude for the city’s miraculous survival which was widely attributed to divine intervention.

Reorganizing the army and maximizing its strength

Heraclius transformed the Byzantine military into a more effective and mobile fighting force. He reduced reliance on static defensive strategies, emphasizing mobile and offensive tactics instead. He reorganized the Byzantine forces into smaller, highly disciplined units and introduced the theme system, laying the groundwork for future military success. The Byzantine army reached peak efficiency under his leadership, with Heraclius himself often leading his troops into battle.

The theme system replaced the traditional Roman administrative divisions, which had remained largely unchanged since the time of Diocletian. Under this new system of provincial administration, he divided the empire into provinces called Themes. The state placed each theme under the authority of a general-governor. He would hold local power over military, economic, and judicial matters. The armies within each Theme were composed largely of military landowners. This system allowed the empire to maintain a capable army for provincial defense. At the same time it ensured a decent standard of living for its subjects for centuries.

Over time, the term Theme acquired a dual meaning. It referred both to a province and to the military body responsible for organizing and defending its territory.

Heraclius also attempted to resolve religious divisions within the empire by promoting Monothelitism. It was a theological compromise aimed at reconciling Chalcedonian Christians and Monophysites. However, this policy ultimately failed to unify the empire.

Notably, the emperor Heraclius established Greek as the official language of the Roman state, replacing Latin. He substituted the title “Imperator Caesar, Augustus” with “Basileus” in official documents, inscriptions, and coins. This shift reflected the empire’s contraction to regions predominantly inhabited by Greek-speaking populations rather than Latin-speaking ones. This explains the emperor’s decision for replacing Latin language with Greek.

Campaigns against the Persians and the recovery of the Holy Cross

In 614, Palestine fell into the hands of the Persian general Sar-Baraz, serving under King Chosroes II. He massacred 90,000 Christians and seized the religious relic of the Holy Cross from the Church of the Holy Sepulchre in Jerusalem. He transported it to the Persian capital, Ctesiphon. In 618, with Constantinople under simultaneous siege by the Persians and the Avars, Heraclius devised a plan to transfer the Roman capital to Carthage and the more stable exarchate of Africa. However, he eventually abandoned the plan after the Ecumenical Patriarch Sergius I persuaded him.

Heraclius began his campaign in 622, after 12 years of meticulous preparation. He faced the Persian general Sar-Baraz at Issus, where he achieved a brilliant military success. In 623, he headed north to Trebizond and later scored another victory over the Persian forces at Nineveh. From Trebizond, he marched to the Persian capital of Ctesiphon. In 624, he achieved a new victory against the Persians, and in March 625, without returning to Constantinople, he embarked on a long march north to Amyntas. There, he confronted Sar-Baraz again on the battlefield and, with his personal courage, turned an impending defeat into a decisive victory.

In Trebizond, Heraclius thwarted the plans of the Avar Khagan to attack Constantinople. He divided the Roman army into three corps: one he sent to Constantinople, another to Mesopotamia, and the last—under his personal leadership—remained in Trebizond. During his absence, Constantinople fell under the informal political leadership of Patriarch Sergius, who took measures for a successful defense, mobilizing the populace on a massive scale. Meanwhile, in Mesopotamia, Heraclius’ brother Theodosius destroyed the Persian army, while the Emperor conducted mopping-up operations.

Heraclius: A victorious hero

According to the historian Theophanes the Confessor, Heraclius personally engaged in combat during this campaign, reportedly killing Rhazates in single combat. This act was symbolic and morale-boosting, demonstrating his courage and inspiring his troops to victory.

In 626, Heraclius confronted the Persians again at Nineveh. The victory came after a personal duel between the Emperor and the Persian general Razatis. The continuous defeats led to the fall of Chosroes II’s regime. It marked the definitive end of the Persian threat to Constantinople. The Sassanid Empire began its decline, eventually collapsing in 651, years after the Byzantine victory.

Heraclius returned triumphantly to Constantinople on September 14, 628, entering through the Golden Gate. Before him was the relic of the Holy Cross, recovered from the Persians. They praised the emperor, then 54-years-old, as a hero, though he was physically and mentally exhausted.

At around the same time, Islam and the Arabs emerged, replacing the Persian threat. Palestine fell to the Muslims in 633, and within less than a century, North Africa, the Iberian Peninsula, Syria, and Antioch were among their conquests. Heraclius watched in despair as the provinces he had dedicated his life to liberating fell. His mental health deteriorated, particularly after the devastating defeat of a Byzantine force of 80,000 men at the Battle of the Yarmouk River in Galilee in 636. This was followed by further losses to the Arabs and their leader, Khalid ibn Walid, who conquered all of Palestine, Jordan, and Syria, reaching as far as Antioch and Germanica.

Heraclius never regained either his mental or physical health. He died in February 641 and was buried in the Church of the Holy Apostles.