Who spread Christianity in the Roman Empire

Emperor Constantine (ca A.D. 280– 337) reigned over a major transition in the Roman Empire—and much more. His acceptance of Christianity and his establishment of an eastern capital city, which would later bear his name, mark his rule as a significant pivot point between ancient history and the Middle Ages.

The Roman Empire that Constantine was born into was one of chaos and anarchy. Civil wars, invasions, and disease were rending the empire so badly that the era is regarded as the Crisis of the Third Century. Emperor Diocletian tried to bring order by distributing power to a four-ruler tetrarchy that would govern the four quarters of the empire. Constantine’s father, Constantius I, was one of the rulers.

Ancient Rome 101

Spanning over a thousand years, ancient Rome was a civilization of constant evolution. This great empire flourished through innovation and incorporation of the diverse cultures they conquered, such as the adoption of Latin and gladiatorial combat. Learn about the rise and fall of this ancient civilization and how its influence still endures today.

Diocletian’s plan fell apart. After the death of his father in A.D. 306, Constantine was declared emperor by his father’s soldiers. He spent the next 18 years battling the three other Roman rulers—his rivals—to become the sole emperor.

The Battle of Milvian Bridge outside Rome in A.D. 312 was a watershed moment for Constantine. He defeated one rival, his brother-in-law Maxentius, and gained the mantle of western Roman emperor. But of far greater import was a revelation he experienced before the battle.

According to Constantine’s biographer Eusebius, Constantine and his forces saw a cross of light in the sky, along with the Greek words for “In this sign conquer.” That night, Constantine had a dream in which Christ reinforced the message. The emperor marked the Christian symbol of the cross on his soldiers’ shields. When he triumphed at Milvian Bridge, he attributed the victory to the god of the Christians. Modern scholars still debate the tale and whether Constantine’s conversion was sincere or a political maneuver. Regardless, in A.D. 313 Constantine met with Licinius, the eastern emperor, and together they issued the Edict of Milan. The edict granted “to the Christians and others full authority to observe that religion which each preferred.”

In this Byzantine mosaic, dating from the 9th century, the Virgin Mary and child are seated between the Emperors Justinian (left) and Constantine (right).

Christianity emerged in the far reaches of the Roman Empire sometime around A.D. 26 or 27, when Jesus of Nazareth began his public ministry. Attracting large crowds throughout his native Galilee (in modern-day Israel), he preached a message of forgiveness, love, and renewal. He talked about fulfilling the Scriptures but stopped short of openly declaring himself the “Messiah,” the savior of the Jewish nation prophesied in the Hebrew Bible. Jesus was arrested on charges of blasphemy and crucified around A.D. 30. The Bible tells that Jesus rose from the dead three days after his Crucifixion. His followers called him “the Christ,” or the “anointed one,” and referred to themselves as Christians. They began to spread the Gospel, the “good tale,” of his life and ministry.

A change of scene

Constantine assumed sole control over the empire in A.D. 324. Rome, however, was losing its luster for him. Tensions remained high between the city’s pagans and the Christian emperor. Moreover, from a military standpoint, Constantine realized it would be easier to fend off threats from the east and to protect valuable territory—and granaries—in Egypt if he moved his capital to a more defensible eastern location. He left Rome for good to build an imperial city that would glorify both his power and his faith.

Constantinople (modern-day Istanbul), his capital, was dedicated in A.D. 330. Previously known as Byzantium, it had been under Roman control for well over a century, but Constantine rebuilt and expanded it on a monumental scale. He tripled the size of the existing city and offered full citizenship and free bread to encourage men of rank to move there with their families. A large palace and imposing legislative halls established the city’s gravitas as the new capital. Churches began to punctuate the skyline; Christians were welcomed, and other faiths were generally tolerated.

The ascendant Constantinople soon eclipsed Rome. The western empire gradually crumbled until Rome’s fall in A.D. 476. Yet Constantine’s capital—and the Christian foundation he laid there for the empire—continued to thrive for nearly a thousand years.

By the time Constantine established his new capital in A.D. 330, the city that would be called Constantinople had changed hands multiple times among regional superpowers. Darius I of Persia, the Delian League, the Spartans, and Alexander the Great all had ruled the strategic port known as Byzantium on the Bosporus, a strait between the Black Sea and Sea of Marmara. Roman emperor Septimius Severus destroyed the city in A.D. 196 and rebuilt a grander version, which Constantine expanded upon for his New Rome. The city became a prosperous and important center of faith, power, trade, and architecture. The landmark Hagia Sophia (above) was built by Emperor Justinian during the sixth century, the peak of Constantinople’s glory.

This text is an excerpt from the National Geographic special issue The Most Influential Figures of Ancient History.

The Roman Empire - Part Two

The Spread of Christianity throughout the Roman Empire

Jesus only taught for about three years of his life, however, his message has had a lasting impact on our modern world. Jesus had twelve followers, called disciples, who spread his message. One reason for the success of his message was that he spoke in simple words that everyone could understand. At first, only Jews were taught the message of Jesus. In the First Century AD, Paul (Saul) of Tarsus taught the message of Christianity to people other than Jews. Paul travelled throughout the Eastern part of the Roman Empire. Paul spoke to the Galatians, Celts living in Asia Minor. Jesus' message of equality appealed  to the poor and women. These two groups made up most of the new converts to Christianity. Roman roads and the Pax Romana helped to spread Christianity. Many Romans feared the spread of Christianity, because Christian ideas did not agree with the old Roman ways. The Roman Emperor Nero began one of the first persecutions of early Christians in AD 64. It was also in the year AD 64 that the Great Fire of Rome burned much of the city. Despite persecutions, Christianity continued to spread throughout the Roman Empire.

The Romans in Britain

In AD 43, Roman legions invaded Britain under the rule of Emperor Claudius. Some Britons (Celtic people from Britain) accepted the Romans, but many resisted the invasion of their island. In AD 61, Queen Boudicca, leader of the Iceni, a tribe of Britons, led a Celtic revolt against the Romans in Britannia. Her army burned Londinium, the Roman capital of Britannia, but she was eventually defeated. In modern Scotland, Celts called Picts fiercely resisted Roman rule. Emperor Hadrian reigned from AD 117 to 138. Deciding the Roman Empire was large enough, Hadrian ordered the building of Hadrian’s Wall in Britannia. This wall is still standing in Northern England, and was made to separate Roman Britannia from the Picts, who lived in Scotland. Later, in AD 406, the emperor ordered the Roman legions to evacuate (leave) Britannia.

(You can find out more about Hadrian's wall by watch this video clip)

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Problems with the Empire

The Roman Empire was under single-man rule, so the Empire was only as healthy as the man running it. The first emperor, Augustus, had been a wise ruler, so had many of the early emperors, and Rome enjoyed the time of the Pax Romana.  Through the history of the Roman Empire, there were bad emperors from time-to-time. From AD 211 through AD 284, there were a total of twenty-seven emperors, only four of these men died of natural causes. There was no way to remove an emperor, so most were murdered. Loyal soldiers picked emperors by murdering and placing their generals on the throne. This weakened Rome, and signaled the decline of its Empire.

The Empire is Divided 

Emperor Diocletian reigned from AD 284 to305. Diocletian, felt the empire was too large for one man to rule, he divided the empire in two parts (East and West), and established the Tetrarchy (rule of four). Both East and West had an emperor and a junior emperor. After twenty years the emperors were to step down and the junior emperors would take their place. In this way Diocletian hoped to stop the murders and instability of the past several years. After his twenty years as emperor of the East, Diocletian voluntarily stepped down, and retired to his home.  

The Tetrarchy did not end the civil wars of the Roman Empire. In AD 311, two men claimed to be the sole Augustus or emperor. Both men had the fierce loyalty of their armies. One of these men was named Constantine. On October 28, 312 AD, the Battle of Milvian Bridge took place near the city of Rome. Constantine defeated his rival. The night before the battle took place, Constantine claimed to have seen a vision in the sky. He claimed to see the Greek letters chi and rho, the first two letters in the Greek word Christos, and the Latin phrase In hoc signo vinces meaning "In this sign, you will conquer." He instructed his soldiers to paint the chi rho Christian logo on their shields. Though Constantine was not a Christian, his mother Helena was a Christian. Constantine won the battle and became the sole emperor of the entire Roman Empire. He gave credit for his victory to the Christian god.

The Reign of Constantine I

Constantine ruled from AD 313 to 337. He moved the capital of the empire east to the city of Byzantium. Rome itself, in the middle of the empire, had become a less-important city. Byzantium was located in the richer East of the empire on important trade routes. Later the city would be renamed Constantinople, in honor of Emperor Constantine.

One important change under Constantine was that Christians were no longer persecuted. They were allowed to practice their religion in public. Later, Emperor Theodosius (reign AD 379-395) made Christianity the official religion of the Roman Empire. Theodosius, not surprisingly, also put an end to the ancient Olympic Games, which had honored the god Zeus. Theodosius was the last emperor to rule the entire Roman Empire, as it, once again, split in two after his reign, with one emperor ruling the East and one the West.

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 The Western Half of the Empire Weakens

The Western Roman Empire was the weaker, poorer half. In AD 410, Alaric and the Goths, a barbarian group, sacked the city of Rome. This was the first time Rome had been attacked by a foreign army since the Gauls in the days of the early republic, a thousand years earlier. Unable to protect its borders, the Western Roman Empire became over-run by many barbarians.

In AD 451, Attila the Hun, perhaps the most famous of all the barbarians, was defeated by the Romans, and Visigoths at the Battle of Chalons in Gaul (modern-day France). The Huns were the most feared of the barbarian groups because, though most of the barbarians had converted to Christianity, the Huns were not Christian. The Roman leader at Chalons was Aetius, a boyhood friend of Attila. Aetius had spent some of his youth living as a hostage in the barbarian camp of the Huns.

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(Watch the video below about the Battle of Chalons, a turning point in history)

Disclaimer: By clicking on any links the user is leaving the Penfield School District website, the district is not responsible for any information associated with these links.

In AD 476 the last Roman Emperor of the West, Romulus Augustulus, only in his teens, was replaced by the barbarian king, Odoacer. The Western Roman Empire had finally fallen. The Eastern half of the Roman Empire would continue on for another thousand years, there, the Roman emperor in Constantinople was wealthy enough to pay tribute to barbarians, like the Huns, so they would not invade the East.

We will read more about the surviving Eastern Roman Empire, or Byzantine Empire, and what happened in Western Europe, when we read about the Middle Ages in the following online chapters.