Theodosius I: The Anti-Pagan Roman Emperor who made Christianity the Official State Religion

Theodosius the Great

Theodosius I, also known as Theodosius the Great, was a Roman emperor who reigned from 379 to 395. He is best known for making Christianity the state religion of the Roman Empire and his numerous building projects in the empire’s capital, Constantinople.

About half a century after Constantine the Great (reign: 306-337) began repressing pagans in the military colony of Aelia Capitolina (i.e. Jerusalem), Emperor Theodosius I (reign: 379-395) turned up the heat on the ban on pagan religious practices and made Nicene Christianity the official state religion. Did this decision have anything to do with Theodosius’ upbringing? And how severe were Theodosius’ anti-pagan policies?

Below, World History Edu takes a quick dive into the life, reign and major accomplishments of this ruler of the late Roman Empire.

Quick Biography

Theodosius was born in Spain on 11 January, 347 to a high-ranking military officer (i.e. magister equitum) called Theodosius the Elder and Thermantia. According to epitome de Caesaribus, this future Roman emperor was born at Cauca in Hispania. There are some accounts that state that he was born in Italica. Some have said that this assertion was made in order to connect him to Emperor Trajan (reign: 98-117) who was born in Italica.

A young Theodosius received a very sound education, military and civil. He was said to be big admirer of history.

In his youth, he served under his father in many military campaigns, including the ones against the Scots, Saxons, and Franks. Those campaigns were aimed at consolidating the power of Roman emperors Valentinian I and Valens in Roman Britain.

Theodosius and his father also embarked on military campaigns against the Alamanni in the late 360s and early 370s. It was around that period, he was elevated to the position of dux (duke) of the province of Moesia Prima. He also replaced his father as commander in Illyricum

Also in the early 370s, he was able to restore order to the province of Valeria by defeating the Quadi and their allies the Sarmatians. On the back of those impressive military results, he was appointed magister equitum in the late 370s.

He was chosen by then-Western Emperor Gratian (reign: 367-383) to rule (i.e. augustus) the eastern part of the Roman Empire after the death of the previous emperor, Valens at the Battle of Adrianople in 378.

One of the most significant actions of Theodosius’ reign was his efforts to establish Nicene Christianity as the official religion of the Roman Empire. He declared Nicene Christianity the state religion in 380 CE, and his reign saw the suppression of many pagan practices and beliefs.

Theodosius was also known for his military campaigns against the Goths, who had invaded the eastern provinces of the Roman Empire. He managed to defeat them and force them to accept Roman rule, and he also successfully campaigned against the usurper Magnus Maximus, who had seized control of Britain, Spain, and parts of Gaul.

After his death on January 17, 395 CE, his two sons – Arcadius (reign: 383-408) and Honorius (reign: 393-423) – took over the Eastern and Western empires, respectively. His successors, especially his sons, failed to properly fill the large boots left behind. The two imperial courts ended fighting each other, which paved way for the empire to be susceptible to foreign attacks. That in turn, weakened the empire until the fall of the Western Empire in the late 5th century. However, the Eastern part of the empire, i.e. the Byzantine Empire, lasted for another 1000 years.

Theodosius is remembered as one of the last great emperors of the united Roman Empire and as an important figure in the history of Christianity. It is no wonder he is also known as Theodosius the Great.

He is often seen as the last Roman Emperor to rule before the Empire was permanently split between the West and East.

His first marriage was to Aelia Flaccilla. The marriage produced children – Arcadius, born in 377, and Honorius, born around 384.

The Great Conspiracy (367-368)

Described by the Roman soldier and historian Ammianus Marcellinus, the Great Conspiracy (known in Latin as barbarica conspiratio) was a turmoil that arose in Roman Britain (Rome’s province in Britain) after some Roman deserters connived with Picts from Caledonia. Those forces managed to enter Britannia to link up with invading forces of Attacotti, Scotti, Saxons, and Franks.

The rebels combined with the invaders successfully ran amok in Rome’s northern province, overwhelming many of the empire’s outposts and settlements. They looted and took many Romano-British as slaves.

Solidus of Valentinian I showing Valentinian and Gratian on the reverse. Solidus is highly pure gold coin issued in the Late Roman Empire and Byzantine Empire.

Emperor Valentinian I sent one of his most trusted commanders Flavius Theodosius. The Roman marched his army, which included his son Theodosius, and crossed the Channel. He arrived in the spring of 368 and began bringing order to places that had been overran by the invaders and rebels.

Operating from his base in Londinium (present day City of London), then-capital of Roman Britain, Theodosius and his son used a blend of military and political maneuvers to bring the whole situation under control. After establishing a new province Valentia, which he named in honor of Emperor Valentinian, Theodosius and his son left Roman Britain. The two men were treated as heroes, with the later promoted to magister equitum.

Ides of March: Origin Story & Major Facts

Elevation to augustus in the East

After a well-orchestrated conspiracy that claimed the life of his father in 376, Theodosius lost many of his military portfolios. At the time, he was busy in a military campaign against the Sarmatians. He was relieved and only managed to come out of the situation alive.

His luck turned when Emperor Gratian, the eldest son of deceased emperor Valentinian I, appointed him magister equitum in the late 370s. He was able to return to his military command of the campaign against the Sarmatians.

In Roman Emperor Valens, ruler of the eastern half of the empire, was killed by the Goths at the Battle of Adrianople in 378. With an impressive military experience, Theodosius was deemed the obvious candidate to keep the barbarians from making further incursions into the empire through the Balkans.

On 19 January, 379 at a ceremony in Sirmium, Theodosius was elevated to augustus of the Eastern Empire by then-Western Emperor Gratian (reign: 367-383).

Theodosius I’s campaigns against the Goths

Upon becoming ruler of the East, he immediately set out to get rid of the Goths that were making themselves a huge menace in the Balkans. Although not given much in terms of resources from Gratian, he received the full backing of his western counterpart.

As he realized that the forces of the eastern part of the empire had been depleted following the disaster at Adrianople, he began recruiting new soldiers. He even conscripted carpenters, miners and pottery makers. He imposed steep punishment on any soldier who deserted.

Those strategies helped him bring control to those regions, and he even received the submission of some Gothic leaders, including Athanaric.

However, having realized that Goths could not be defeated outright, he began extending some form of olive branch to them. The Romans and Goths were able to come to an amicable agreement in late 382. Theodosius then allowed the Goths and other barbarians to establish an autonomous region in thos border areas, including those south of Danube. The idea was to use those settled Goths in the empire to fight for Rome.

During Theodosius I’s celebration ceremony of quinquennelia in 383, he elevated his eldest son Arcadius to co-emperor. Image: Roman Emperor Arcadius – son of Emperor Theodosius I

Treaty with the Sasanian Empire

In 383, his colleague Emperor Gratian was murdered by Andragathius, the magister equitum of a usurper called Magnus Maximus (reign: 383-388). The usurper placed himself as ruler of the imperial province of Britannia and Gaul. With his ally gone in large parts of the West, Theodosius struck a treaty with the Persian emperor Shapur III (reign: 383-388) of the Sasanian Empire.

He was also able to broker a peace treaty between Magnus Maximus and Valentinian II in 384.

Image: Solidus of Theodosius, showing both him and his co-emperor Valentinian II (reign; 375–392) enthroned. On the reverse side each emperor crowned by Victory and together holding an orb victoria augg (“the Victory of the Augusti”).

He defeated Magnus Maximus in 388

The peace that he brokered between his colleague emperor Valentinian II and Magnus Maximus lasted until 387. Magnus invaded the territory of Valentinian and forced the young emperor to flee to the East. Upon arriving at Thessalonica, he besieged Theodosius to intervene. And as Valentinian had become Theodosius’s brother-in-law [through his marriage to Galla, the sister of Valentinian], Theodosius decided to offer his support.

In the final battle which took place near Siscia (in modern day Croatia) in 388, Theodosius defeated Magnus Maximus. In August of that year, the usurper ruler of the West was taken into custody and killed at Aquileia (in today’s Friuli-Venezia Giulia, Italy).

Image: Solidus of Magnus Maximus, the Roman Emperor in the West

The Massacre of Thessalonica

In some accounts, Theodosius I was blamed for the Massacre of Thessalonica in Macedonia around 390. The carnage occurred after the death of a Roman official during an urban riot. The Roman official had arrested a famous local charioteer on the charge of rape. When the official refused giving into the people’s demand for the chariot racer’s release, a riot ensued.

During the riot, the Roman garrison commander of Illyricum was taken out of his home and lynched by the rioters. Roman soldiers then went on the rampage and slaughtered many innocent civilians. More than 6500 people were killed in the massacre in just a few hours at the hippodrome of Thessaloniki.

Massacre in the Hippodrome of Thessaloniki in 390

Massacre in the Hippodrome of Thessaloniki in 390, 16th-century wood engraving

In some accounts of the story, it is stated that the emperor was not even in Thessalonica at the time of the massacre. This is because his court at the time was situated in Mediolanum (Milan)

Regardless, Theodosius openly took responsibility for the massacre and tried to save face by showing some sort of repentance in public. One of his closest advisors, Ambrose (339-397), the bishop of Milan, admonished him and forbade the emperor from receiving the Eucharist for a period of time until his sins were absolved. In the end, and through cooperation, Theodosius was readmitted by Ambrose after eight months.

Defeated the usurper Eugenius (reign: 392-394)


Eugenius was a usurper in the Western Roman Empire (392–394). After defeating Eugenius, Theodosius I became ruler of the whole empire.

During his reign, he marched to the West twice – the first was to defeat Magnus Maximus, and the second was to defeat another usurper Flavius Eugenius (reign: 392-394). This military intervention came after the death of the Western emperor Valentinian II in May 392.

It is said that Valentinian was possibly killed in a plot orchestrated by Arbogast, a former general of Theodosius that served as Valentinian’s magister militum. Arbogast maintained his innocence, stating that his master had instead committed suicide.

As Arbogast could not crown himself emperor because he was not a Roman, he proceeded to crown Eugenius, Valentinian’s master of correspondence, emperor in the West.

When news of this reached Theodosius, he was livid and made his son Honorius emperor of the West. This meant that Eugenius was seen as a usurper. Making matters worse the fact that Eugenius, although a Christian, steadily began supporting paganism in the West. He even caved in to the petitions of pagan senators to have the Altar of Victory restored within the Curia.

In 394, Theodosius marched his army and faced off against Eugenius’ forces. Despite the usurper receiving support from Flavianus, a general that was appointed praetorian prefect of Italy by Theodosius, Theodosius’ forces secured victory over Eugenius at the Battle of the Frigidus in early September 394. The usurper was captured and later executed.

How did Theodosius the Great die?

After battling with a disease that caused fluid to build up in his body’s tissue, Roman emperor Theodosius I passed away in Milan on January 17, 395. His panegyric (i.e. a public speech in praise of someone) was delivered by Abrose. The emperor’s body was buried in the Church of the Holy Apostles in Constantinople.

Upon his death, he was deified as Divus Theodosius, which means ‘the Divine Theodosius’.

His successors

Theodosius the Great was succeeded by his two sons – Arcadius (reign: 383-408) and Honorius (reign: 393-423). They took over the Eastern and Western empires, respectively. Their reigns paled in comparison to Theodosius’ reign.

For example, it was during the ineffectual reign of Emperor Honorius that Alaric the Gothic king sacked the city of Rome and destroyed many important buildings, including the old Senate House. The sack of Rome in 410 was the first time in over 800 years that Rome found itself in that dire situation. What was even worse was the fact that Honorius’ sister Galla Placidia was kidnapped during the sack.

Notable Achievements of Theodosius I

The following are some major feats accomplished by Theodosius the Great:

The Obelisk of Theodosius in the Hippodrome of Constantinople

He was the first emperor of the Theodosian dynasty which ruled from 379 to 457. Image: Hippodrome of Constantinople with the surviving Obelisk of Theodosius in Istanbul, Turkey

Due to his love for art, Theodosius I’s reign is said to have ushered in the Theodosian renaissance. Also, during his reign, a massive obelisk was brought from Alexandria in Egypt to Constantinople in 390.

The obelisk was one of two obelisks that were originally in Karnak, Egypt, before they were shipped to Alexandria in 13/12 BC during the reign of Augustus, Rome’s first emperor. The first (i.e. the Lateran obelisk) was shipped from Alexandria to Rome by Constantius II in 357.

The reason for Theodosius shipping the second obelisk from Alexandria to Constantinople was to celebrate his victory over the usurper emperor Maximus Magnus. The obelisk, which came to be called the Obelisk of Theodosius, was placed in the famous Hippodrome of Constantinople.

The two obelisks were constructed by 18th dynasty Egyptian pharaoh Thutmose III (c. 1479-1425 BC) and placed in the Great temple of Karnak. They were used to celebrate the Egyptian pharaoh’s victory over the Mitanni (people that inhabited northern Syria and southeast Anatolia) on the banks of the Euphrates around 1450 BC.

He built the Forum of Theodosius – the biggest public square in antiquity

Taking cues from Trajan’s Forum in Rome, Theodosius I was able to rebuild the Forum Tauri (known as the Forum of the Bull) in Constantinople. The public square was originally built by Constantine I; however, it was Theodosius who rebuild it in 393, making it the largest in antiquity. The square had the famous Column of Theodosius, a triumphal column, situated at the center, as well as a triumphal arch.

How Theodosius I resolved the debate between Arianism and Orthodoxy

The emperor Theodosius I and a crowd of bishops seated on a semicircular bench at the First Council of Constantinople in 381

First developed by a Christian presbyter priest called Arius (250-336), the doctrine of Arianism emphasizes the subordination of the Son (i.e. Jesus Christ), and even sometimes the Holy Spirit, to the Father (i.e. God). It states that as Jesus Christ is the Son of God, however, it goes on to say that the Son of God did not always exist but was instead begotten before time by God the Father. This means that Jesus was not coeternal with God the Father. In some extreme forms of Arianism (i.e. from Aetius and Eunomius), it is claimed that the Son is similar to the Father, but the Son is not the same in essence to the Father, making the Son subordinate to the Father.

The interpretations of Jesus’s divinity by the Arian theology did not agree with the theological orthodoxy (i.e. the Trinitarian orthodoxy of the Homoousian Christians) of the time. The Homoousion theology believes that Jesus (i.e. God the Son) is the same in essence and being with God the Father. Also to the Homoousion Christians, the Holy Spirit is the same in essence with the Son and the Father. Those Christians would form Nicene Christianity.

Christian Orthodoxy and the Nicaean Creed in the late Roman Empire

In addition to condemning Arians as heretics, members at the First Council of Constantinople condemned Apollonarian and Macedonian doctrines as heresies.

In the first ecumenical council, i.e. the First Council of Nicaea held in the Bithynaian city of Nicaea (present day İznik, Turkey) by Constantine in 325, it was declared that the Son was true God and coeternal with the Father.

With the debate still raging between Arianism and Nicene Creed, Theodosius convened the second ecumenical council in 381. Known as the First Council of Constantinople, the council of religious leaders that met in the Church of Hagia Irene confirmed the Nicene Creed, an orthodox position. The emperor, who strongly leaned to the Nicene Creed, wanted the Eastern Church to move away from Arianism and return to the Nicene Creed.

The Edict of Thessalonica

By issuing the Edict of Thessalonica on 27 February 380, Theodosius condemned non-Nicene Christians, including Arians, as heretics. Also Catholicism was reserved only for Nicene Christians. He thus cemented Christian orthodoxy as the state church of the Roman Empire.

The Edict ended being a huge cornerstone in the Christianization of the Roman Empire. Any church leader that refused to accept the creed of Nicea was removed from office.

For example, he removed Acacian bishop Demophilus and replaced him with Gregory of Nazianzus. Many advocates of the Nicaean doctrine were given top positions in the clergy. Arian sympathizers were persecuted and stripped off their property and positions.

Baptism and Sainthood

In 380, Theodosius was baptized by a local Nicene bishop called Ascholius. His baptism came after his near-death experience with a bad illness. Theodosius was not new to the Christian faith. His father, for example, got baptized before his death.

For his efforts in suppressing paganism and promoting Nicene Christianity, Theodosius the Great is revered as a saint by a number of churches, including the Oriental Orthodox and Eastern Orthodox.

Demise of paganism in the Late Roman Empire

Persecution of pagans in the late Roman Empire began during the reign of Constantine the Great, the first Roman emperor to convert to Christianity. Constantine is believed to have ordered the destruction of a pagan temple (believed to be the temple of Aphrodite built by Emperor Hadrian) in Jerusalem (i.e. formerly the military colony of Aelia Capitolina) in order to build a Christian church.

Icon depicting Constantine I, accompanied by the bishops of the First Council of Nicaea (325), holding the Niceno-Constantinopolitan Creed of 381

By issuing the Edict of Milan in 313, Constantine gave legal rights to Christian. He thus halted the centuries-old persecutions and torture practice against Christians. Constantine’s policies allowed Christians to reclaim properties, including those on holy sites, which had been confiscated by previous pagan Roman rulers.

Constantine’s successors, with the exception of Emperor Julian (reign: 361-363), not only intensified their anti-pagan policies they also increased the penalties for carrying out pagan rituals and sacrifices.

There were even cases that some pagans were threatened with death penalties. In Roman Italy for example, some pagan rituals were treated as capital crimes during the co-reigns of Constantine’s sons – Constantius II, Constantine II, and Constans I. For example, Constantius II (reign: 337-361) had a personal maxim: “Cesset superstitio; sacrificiorum aboleatur insania”, which means “Let superstition cease; let the folly of sacrifices be abolished”.

As part of Constantius II’s efforts to repress the practices of pagans he even removed the Altar of Victory from the Roman Senate. It is said that the altar was placed there by Augustus, Rome’s first emperor, in 29 BC so that senators could make sacrifices upon it before entering the Senate.

Although without any substantial evidence, Constantius II likely imposed the death penalty on anyone who consulted soothsayers. His anti-pagan policies were, however, opposed by governors and elites across the empire – an empire that was still predominantly made up of pagans. This made his anti-pagan policies relatively ineffective.

Similarly, Emperor Gratian (reign: 367-383) was known for his strong anti-pagan policies – so much so that some pagan senators openly protested against them.

Theodosius I’s persecution of pagans

During Theodosius I’s reign, he reinforced many of those anti-pagan policies, especially those on animal sacrifice and apostasy. He did, however, allow those animal sacrifices to be done publicly, albeit heavy disgust from Christians. He also allowed some pagan temples to remain standing.

Ambrose, the Bishop of Milan, managed to convince him to reduce the level of financial support for paganism from the state. Instead, he channeled those funds into the support of Nicene Christians, granting them gifts of money and land as well high-ranking positions in the clergy.

In some cases, the pagan temples were deconsecrated. They did this by removing the cult statue and altar from the temple and then using them as churches. In other cases, the hands and feet of the statues were mutilated – including heads and genitals.

Sometimes, the Christians carried out purges by setting fire to pagan statues and altars just to show how impotent those gods were. They also took to chiseling crosses on the statues as a way to rid them of what they considered bad spirit.

It is said that Emperor Theodosius and some Christian emperors of the late Roman Empire allowed pagan temples to remain because he saw them as remarkable artworks worth preserving.

The Serapeum remains in Alexandria

In the later part of his reign, Theodosius issued many decrees (i.e. Theodosian decrees) that clamped down on paganism, Hellenistic religion, and Arianism. For example, many Hellenistic temples of antiquity like the Temple of Apollo in Delphi and the Serapeum in Alexandria were destroyed while he looked the other way. Image: The Serapeum remains in Alexandria

However, in some cases, the emperor chose to look the other way when some Christian zealots destroyed pagan holy sites and temples. For example, refused to bring to book his praetorian prefect Maternus Cynegius who went on a rampage and damaged many pagan shrines in the eastern provinces.

Another thing that he did was to make pagan holidays workdays. He allowed pagans to continue celebrating their festivals because he did not want to make them feel repressed. Bear in mind, pagans still made a significant percentage of empire’s population at the time.

It’s also very important to mention the fact that many local officials and magistrates were pagans. As result, Theodosius’ anti-pagan laws would have most likely been imposed in a very lax manner. It is also not unlikely that Theodosius and his Nicaean Christian officials were more interested in putting down heresy than paganism.

Other anti-pagan decrees by Theodosius the Great

In the decades that followed after his reign, his anti-pagan decrees were further strengthened; and ultimately his successors eliminated public sacrifices for good. Here are a few more things about Theodosius anti-pagan policies:

  • With the last Ancient Olympic Games taking place in 393, it is believed that either Theodosius I, or his grandson Theodosius II in 435, suppressed them
  • Theodosius ordered for the eternal fire in the Temple of Vesta in the Roman Forum to be extinguished.
  • Some of his decrees clamped down on the activities of augury and witchcraft. The former refers to people who interpreted omens from observed behavior of birds.

Theodosius the Great’s family

He first wife was Aelia Flaccilla, by whom he fathered children – Arcadius, born in 377, and Honorius, born around 384. After the death of Aelia Flaccilla in 383, he remarried. His second wife, Galla, hailed from the powerful Valentinianic dynasty (reign: 364-455). Galla was the half-sister of Emperor Gratian and daughter of Valentinian the Great (reign: 364-375). Theodosius and Galla had children: Gratian and Galla Placidia. The former was born either in 388 or 389.

Theodosius I's spouses

Aelia Flaccilla – wife of Emperor Theodosius I

His father, Count Theodosius (also known as Flavius Theodosius) held a high rank in the military – the magister militum – which is equivalent to the modern day commander of a war theatre. Thus, Theodosius the Elder reported only to the Western Roman emperor Valentinian I (reign: 364-375), who served as the supreme commander. He was executed at Carthage in 376 as he was considered a potent threat to the new emperors Gratian and Valentinian II. Upon Theodosius elevation to augustus in 379, Theodosius the Elder was deified as Divus Theodosius Pater, which means ‘the Divine Father Theodosius’.

Theodosius I: Fast Facts

Born: 11 January, 347

Died: 17 January, 395

Buried: Church of the Holy Apostles, Constantinople

Parents: Theodosius the Elder and Thermantia

Spouse: Aelia Flaccilla (376-386) and Galla (387-394)

Children: Arcadius, Honorius, Pulcheria, Gratian, Galla Placidia.

Religion: Nicene Christianity

Reign: 379-395

Predecessor: Valens

Successors: Arcadius (Eastern Roman Empire) and Honorius (Western Roman Empire)

Best known for: Making Christianity the state religion of the Roman Empire



Brown, Peter. Through the Eye of a Needle: Wealth, the Fall of Rome, and the Making of Christianity in the West, 350–550 AD. Princeton University Press, 2012.

Cameron, Alan. The Last Pagans of Rome. Oxford University Press, 2010.

Errington, R. Malcolm. Roman Imperial Policy from Julian to Theodosius. Chapel Hill: University of North Carolina Press, 2006.

Glenn, Hinson, E. The church triumphant: a history of Christianity up to 1300. Mercer University Press, 1995.

King, N.Q. The Emperor Theodosius and the Establishment of Christianity. London, 1961.

MacMullen, Ramsay. Christianizing The Roman Empire AD 100–400, Yale University Press, 1984.

Williams, Stephen; Friell, Gerard. Theodosius: The Empire at Bay. Yale University Press, 1995.

Leave a Reply

Your email address will not be published. Required fields are marked *