Table of Contents
The End of the Tetrarchy and the Beginning of a Christian Empire
The collapse of Diocletian’s Tetrarchy triggered a new series of civil wars that reshaped the Roman Empire. Out of this turmoil emerged Constantine the Great, one of the most influential emperors in Roman history. His reign marked the transition from the classical pagan empire to a Christian imperial state and laid essential foundations for the Byzantine Empire.
The Constantinian Dynasty includes the reigns of:
- Constantine I “the Great” (306–337 CE)
- His sons and relatives:
- Constantine II (337–340 CE)
- Constantius II (337–361 CE)
- Constans (337–350 CE)
- Julian (“the Apostate,” 361–363 CE)
Together, they shaped a transformative era in Late Antiquity.
The Collapse of the Tetrarchy and the Rise of Constantine
Struggle for Power (306–312 CE)
After Diocletian’s retirement, the Tetrarchy quickly fell apart. When Constantius Chlorus (Augustus of the West) died in 306 CE, his troops proclaimed his son Constantine emperor—ignoring the planned succession.
At the same time:
- Maxentius, son of former Augustus Maximian, seized power in Rome
- Galerius attempted to preserve the Tetrarchy
- Different generals and Caesars made competing claims
By 312 CE, multiple emperors were fighting for control.
The Battle of the Milvian Bridge (312 CE)
A Decisive Victory and a Turning Point
The key moment in Constantine’s rise was his clash with Maxentius near Rome. Before the battle, Constantine reportedly had a vision of a Christian symbol (the Chi-Rho) with the words “In this sign, conquer.”
During the battle:
- Constantine’s forces defeated Maxentius
- Maxentius drowned in the Tiber River
- Constantine entered Rome as the sole ruler of the Western Empire
This event is often seen as the symbolic beginning of the Christianization of the Roman Empire.
Constantine as Sole Ruler (324–337 CE)
After defeating his eastern rival Licinius in 324 CE, Constantine became the sole emperor of a reunited Roman Empire—something no one had achieved since Diocletian.
Major Achievements
- Legalization of Christianity
- Issued the Edict of Milan (313 CE), granting religious tolerance
- Restored property to Christian communities
- Supported Christian clergy and churches
- Presided over the Council of Nicaea (325 CE), which produced the first universal Christian doctrine (the Nicene Creed)
Constantine did not outlaw paganism, but he shifted imperial favor toward Christianity.
Founding Constantinople
In 330 CE, Constantine established Constantinople on the site of ancient Byzantium.
It became:
- A new imperial capital
- A Christian metropolis
- Strategically located between Europe and Asia
Constantinople would remain central to the Eastern Roman (Byzantine) Empire for over 1,000 years.
- Administrative and Military Reform
- Continued Diocletian’s separation of civil and military power
- Reorganized the army into mobile field units and frontier troops
- Issued new gold coins (solidus) that stabilized the imperial economy
- Strengthened the court and bureaucracy
Constantine’s reforms further centralized imperial power.
The Constantinian Succession (337–361 CE)
After Constantine’s death in 337 CE, his empire was divided among his three surviving sons.
Constantine II, Constantius II, and Constans
- Constantine II ruled the West but was killed in conflict with his brother Constans
- Constans ruled Italy and Africa but was assassinated by the usurper Magnentius
- Constantius II eventually defeated all rivals and reunited the empire under his rule (351–361 CE)
Constantius II was deeply religious and continued promoting Christianity, often intervening in theological disputes.
Julian the Apostate (361–363 CE)
A Brief Attempt to Restore Pagan Traditions
Julian, nephew of Constantine and a talented general, became emperor after Constantius’ death.
His Goals
- Reverse the Christian favoritism of previous rulers
- Restore traditional Roman polytheistic worship
- Reduce the involvement of bishops in state affairs
- Promote Neoplatonic philosophy
Julian’s policies earned him the nickname “Apostate” among Christians.
His Death and Legacy
Julian died in 363 CE during a Persian campaign. His attempt to return Rome to paganism collapsed immediately, and Christianity remained firmly established as the dominant imperial religion.
Legacy of the Constantinian Dynasty
The Constantinian era fundamentally transformed the Roman Empire:
Political Legacy
- Permanent shift of power toward the East
- Establishment of Constantinople as a second Rome
- End of the Tetrarchy and return to dynastic succession
Religious Legacy
- Christianity became a favored—and eventually dominant—religion
- The Nicene Creed became a foundational Christian doctrine
- Church and state grew increasingly interconnected
Cultural and Economic Legacy
- New gold coinage (solidus) provided lasting economic stability
- Growth of Christian art, architecture, and scholarship
- Emergence of a Christian imperial identity
The Constantinian Dynasty bridged the gap between the classical Roman world and the early medieval Christian world.