Sunday School Review: Basic Church History: Nicaea through the Middle Ages, Part 11

Devastating wars marked the century between 632 and 732 AD, the rise of Islam, and the loss of vast Christian lands to Islamic conquest. The stakes for the church could hardly have been higher. The Eastern Roman Empire (Byzantium), under siege from barbarian and Persian invaders, faced a new and unprecedented challenge in the form of Islam—a monotheistic faith that emerged with staggering speed from the Arabian Peninsula.

Amid these crises, however, the church endured. By God's providence, critical moments of resilience, such as the Battle of Tours, ensured that Christianity would survive and flourish, even in the face of immense losses. This period is both a sobering reminder of the fragility of human institutions and a testament to the unshakable promise of Christ that His church would prevail (Matthew 16:18).

If you’re new here and missed last week's review, you can find it here.

Justinian's Struggles Against the Barbarians

Before the rise of Islam, the Byzantine Empire under Emperor Justinian (r. 527–565 AD) faced the enormous task of reclaiming territories lost to barbarian invasions after the fall of the Western Roman Empire. Justinian sought to restore the glory of Rome, launching campaigns to recover lands that had fallen under the control of the Ostrogoths in Italy and the Vandals in North Africa.

The campaign against the Vandals was swift and decisive. In 533 AD, Justinian's general, Belisarius, led a daring expedition that crushed the Vandal Kingdom and restored North Africa to imperial control. This victory re-established Christian dominance in the region, which the Arian faith of the Vandals had compromised.

The war against the Ostrogoths in Italy proved far more grueling. The Gothic War (535–554 AD) devastated the Italian peninsula, leaving much of its infrastructure in ruins. Though Justinian ultimately succeeded in reasserting Byzantine authority, the cost was immense in terms of lives, resources, and political stability.

These victories, though significant, left the Byzantine Empire overstretched and vulnerable. The financial strain and the thin distribution of military forces made it difficult to respond effectively to new threats on the empire's borders.

Heraclius and the War Against Persia

In the early seventh century, the Byzantine Empire faced one of its greatest existential threats in the form of the Sassanian Persian Empire, a formidable power that had dominated the Near East since the third century. This empire traced its heritage to the Empire of Cyrus the Great, the Persian ruler celebrated in the Old Testament as a deliverer of God’s people. Cyrus, prophesied by the prophet Isaiah long before his birth (Isaiah 44:28–45:1), conquered Babylon in 539 BC and issued the decree allowing the Jews to return from exile and rebuild the temple in Jerusalem (Ezra 1:1–4). His empire also intersected with the life of the prophet Daniel, who served as a high-ranking official during the reigns of Cyrus and Darius, both central figures in biblical history (Daniel 6).

The Sassanian Empire, a later successor to this legacy, carried forward Persian traditions of centralized administration, cultural achievements, and a powerful military rooted in elite cavalry units. Unlike the Islamic empires that would follow, the Sassanian state was deeply tied to Zoroastrianism, a religion emphasizing a cosmic struggle between good and evil. This dualistic faith stood in contrast to the Byzantine Empire’s Christian worldview, and the two empires clashed repeatedly in protracted wars over territory and influence.

In 614 AD, the Sassanians launched a devastating campaign into Byzantine territory, capturing Jerusalem and carrying off the True Cross, a relic revered by Christians as the cross on which Christ was crucified. This act marked the height of their campaign and symbolized their dominance over a region central to both the Jewish and Christian faiths. The capture of the True Cross dealt a severe blow to Byzantine morale and underscored the intense rivalry between these two great powers.

Emperor Heraclius (r. 610–641 AD) rose to the occasion, rallying the beleaguered empire and personally leading a counter-offensive. After years of campaigns, the decisive Battle of Nineveh in 627 AD saw Heraclius achieve a stunning victory over the Persian forces. This victory marked the beginning of the end for the Sassanian Empire, allowing Heraclius to recover Jerusalem and restore the True Cross to the Church of the Holy Sepulchre.

Heraclius' triumph brought a momentary reprieve, but the empire was left weakened by decades of war. The physical and economic toll on Byzantium left it ill-prepared to face a new and more enduring challenge: the rapid expansion of Islam.

The Rise of Mohammed

Mohammed, the founder of Islam, was born in Mecca around 570 AD into the Quraysh tribe, a prominent merchant clan. Orphaned at a young age, Mohammed worked as a caravan trader. His life changed dramatically around 610 AD when he began experiencing what he believed to be divine revelations. These revelations, which he claimed were delivered by the angel Gabriel, were compiled into the Quran (Qur'an), regarded by Muslims as the literal word of God (Allah).

Mohammed's message challenged the polytheism and idolatry of Mecca, proclaiming instead the worship of one true God and calling for moral and social reform. The early years of his ministry were marked by opposition and persecution, but in 622 AD, Mohammed and his followers fled to Medina in the Hijra (Migration). This event marked the beginning of the Islamic calendar.

In Medina, Mohammed established a religious and political community, combining spiritual leadership and governance. By his death in 632 AD, he had united much of the Arabian Peninsula under Islam through military conquest, alliances, and religious fervor.

The Origin and Beliefs of Islam

Islam is a monotheistic religion with core beliefs and practices defined by the Quran and the Hadiths (sayings and actions of Mohammed). Its theological foundation centers on the absolute oneness of God (Tawhid), rejecting any division in God's nature, including the Christian doctrine of the Trinity.

Key Islamic terms and concepts include:

• Shahada: The declaration of faith—"There is no god but Allah, and Mohammed is His prophet."
• Salah: The five daily prayers performed facing Mecca.
• Zakat: Almsgiving or charitable giving, typically set at a fixed percentage of one's wealth.
• Sawm: Fasting during the month of Ramadan as an act of worship and self-purification.
• Hajj: The pilgrimage to Mecca, which every Muslim is required to perform at least once if physically and financially able.

Islam also teaches reverence for earlier prophets, including Abraham, Moses, and Jesus, though it denies Jesus' divinity and the Christian understanding of His atoning work on the cross.

The Rapid Spread of Islam

Following Mohammed's death in 632 AD, his successors, the caliphs, embarked on a series of military campaigns that rapidly expanded the Islamic world. Within a century, Islamic forces had conquered vast territories, including Syria, Palestine, Egypt, Persia, and North Africa. The Byzantine Empire lost some of its most important provinces, including Alexandria and Carthage, while the Persian Empire collapsed entirely.

This expansion continued into Europe, where Islamic armies crossed into Spain in 711 AD, establishing the Umayyad Caliphate. By the early eighth century, Islamic forces had advanced into the Pyrenees, threatening the Christian kingdoms of Western Europe.

The Battle of Tours

The advance of Islam into Europe reached a critical moment in 732 AD at the Battle of Tours. An Islamic army, led by Abd al-Rahman, crossed the Pyrenees into Frankish territory. Their goal was to expand Islamic rule further into Europe, potentially opening the continent to a new wave of conquests.

Charles Martel, a Frankish leader and grandfather of Charlemagne, gathered an army to meet the Islamic forces near the city of Tours. The stakes were immense: if the Islamic army prevailed, it could mark the end of Christian dominance in Western Europe.

For seven days, the two armies faced off in a tense stalemate. Charles' forces, though outnumbered, held a strong defensive position, forming a disciplined phalanx that withstood repeated cavalry charges. The turning point came when Abd al-Rahman was killed in battle. Leaderless and demoralized, the Islamic forces retreated, ending their advance into Europe.

The Battle of Tours was a defining moment in European history. Charles Martel's victory preserved the independence of Christian Europe and earned him the title "The Hammer." This battle ensured that the nascent Christian kingdoms of Europe would have the opportunity to grow and develop, laying the foundation for what would later become Christendom.

The Scale of Losses to Islam

Despite the victory at Tours, the losses to Islam were monumental. By the eighth century, vast swaths of the Christian world—including North Africa, the Levant, and parts of Spain—had fallen under Islamic rule. Cities like Jerusalem, Antioch, and Alexandria, once centers of Christian faith and learning, were now part of the Islamic Caliphate.

These losses were not only territorial but spiritual and cultural. Ancient Christian communities were subsumed, and the church faced the challenge of ministering to believers under Islamic rule.

Causes of Islamic Success

The rapid and extensive success of Islamic expansion can be attributed to a combination of strategic, political, and religious factors that created a perfect storm for conquest. Both the Byzantine and Persian Empires, long-standing rivals in the Near East, were severely weakened by decades of exhausting warfare against one another. This prolonged conflict left their armies depleted, their economies strained, and their territories vulnerable to outside attack.

Adding to this vulnerability was the fervent religious zeal that drove Islamic forces. Motivated by a deep belief in spreading their faith, these armies often saw their campaigns as a divine mission, energizing their soldiers with a sense of purpose that transcended mere territorial ambition. This conviction was bolstered by the political unity of the Islamic world under the caliphs, who provided centralized and cohesive leadership. This organization enabled coordinated and focused military campaigns, which contrasted sharply with the fragmented responses of their adversaries.

The tactical adaptability of Islamic forces further amplified their success. Skilled in desert warfare, these armies were capable of quickly adjusting to new environments and overcoming challenges, whether in the arid expanses of the Middle East or the rugged terrain of North Africa and beyond. This adaptability gave them a decisive advantage over less mobile or flexible foes.

Internal divisions within Christendom also played a significant role in the Islamic conquests. Theological disputes, such as the Monophysite controversy, had fractured Christian communities in the eastern provinces of the Byzantine Empire. These divisions weakened local resistance, as some groups were even willing to accept Islamic rule over continued Byzantine domination. Together, these factors enabled the Islamic empire to expand at an astonishing pace, reshaping the political and religious landscape of the region.

Islamic Effect on the "Pentarchy"

The rapid Islamic conquests of the 7th and 8th centuries profoundly altered the Christian church's leadership structure and balance. Before these conquests, the Christian world was anchored by five major patriarchates: Jerusalem, Alexandria, Antioch, Rome, and Constantinople. These cities, collectively known as the Pentarchy, were seen as the spiritual and administrative hubs of Christendom, each holding significant influence in shaping doctrine, governance, and missionary outreach.

Islamic expansion, however, reshaped this dynamic, severing three of these cities—Jerusalem, Alexandria, and Antioch—from direct interaction with much of the Christian world and leaving Christendom divided into two spheres of influence: the Western church centered in Rome and the Eastern church centered in Constantinople. This division would have far-reaching theological, cultural, and political consequences.

Jerusalem

Jerusalem, as the city of Christ's crucifixion and resurrection, held immense spiritual significance for Christians. However, in 638 AD, following a siege, the city fell to the armies of the Rashidun Caliphate under Caliph Umar. Though Christians were permitted to continue their worship under Islamic rule, their influence was significantly curtailed. The Patriarch of Jerusalem became a subordinate figure, his decisions subject to the oversight of Muslim authorities.

The loss of Jerusalem also marked a psychological blow to the Christian world. The Holy City, the spiritual heart of the faith, was now under the control of a religion that denied the divinity of Christ. Pilgrimage to the city, a vital expression of Christian devotion, became fraught with difficulty and danger, further isolating it from the rest of Christendom.

Alexandria

Alexandria, once a center of Christian scholarship and the home of towering figures like Athanasius and Cyril, fell to Islamic forces in 642 AD. The city had been a hub of theological debate and missionary activity, renowned for its catechetical school, which had shaped much of early Christian theology.

Under Islamic rule, Alexandria's influence waned. The Patriarch of Alexandria, while allowed to remain in office, saw his authority eroded as the majority of Christians in the region—many of whom were Copts—were relegated to dhimmi (protected but second-class) status. Over time, the city's prominence in the Christian world diminished as its intellectual and ecclesiastical contributions were stifled under Muslim governance.

Antioch

Antioch, one of the earliest and most vibrant centers of Christianity, where believers were first called Christians (Acts 11:26), was another significant loss. Conquered by Islamic forces in 637 AD, Antioch became a frontier city in the Islamic caliphates. The patriarchate was reduced in stature and influence, as political and military barriers severed its connections to the rest of Christendom.

Antioch's decline mirrored that of Alexandria and Jerusalem. Once a vital theological and cultural bridge between the Eastern and Western churches, it became an isolated outpost, its patriarch largely cut off from broader ecclesiastical decision-making.

Rome and Constantinople

With Jerusalem, Alexandria, and Antioch under Islamic control, the leadership of the Christian world became increasingly concentrated in the two remaining patriarchates: Rome in the West and Constantinople in the East. This shift created a bipolar structure within Christendom that would define much of its subsequent history.

The Bishop of Rome, already claiming primacy as the successor of Peter, found his position further elevated by the isolation of the eastern patriarchates. Rome became the undisputed center of Western Christianity, exercising authority over the developing Latin-speaking churches of Europe. The loss of eastern territories also allowed the pope to focus more fully on consolidating power within the Western sphere, aligning closely with the emerging Frankish monarchy and other Western rulers.

The papacy's influence would continue to grow, culminating in the crowning of Charlemagne as Holy Roman Emperor in 800 AD, symbolizing the fusion of spiritual and temporal authority in the West. Rome's primacy in the West, however,also laid the groundwork for tensions with Constantinople, as the eastern church increasingly viewed the papal claims with suspicion.

Constantinople, the capital of the Byzantine Empire, remained the spiritual and political hub of Eastern Christianity. The Patriarch of Constantinople, closely aligned with the emperor, assumed a central role in the governance of the Eastern church. With Jerusalem, Alexandria, and Antioch effectively cut off, Constantinople became the primary voice of Eastern Orthodoxy.

This concentration of power in Constantinople also fueled theological and cultural divergence between the East and West. The Eastern church, steeped in Greek thought and traditions, developed practices and theological emphases distinct from those of the Latin-speaking West. Over time, these differences, exacerbated by political rivalries, would culminate in the Great Schism of 1054.

Consequences of the Bipolar Christendom

The loss of three patriarchates to Islam—Jerusalem, Alexandria, and Antioch—and the resulting division of Christendom into Western and Eastern spheres had profound and lasting effects on the church. In the East, with the majority of its historic patriarchates now under Islamic rule, the church became increasingly isolated. Cut off from much of the Christian world, the Eastern church focused on preserving its traditions within the confines of the Byzantine Empire. This inward turn emphasized safeguarding its liturgical practices, theological heritage, and ecclesiastical structure amidst external threats and internal challenges.

Meanwhile, in the West, the church centered in Rome began to expand its influence northward and westward. With its historic ties to the East severed, the Roman church directed its energies toward the conversion of northern and western Europe, forming strong alliances with emerging powers such as the Franks. This expansion laid the groundwork for the establishment of medieval Christendom, with the papacy assuming a more prominent role in both spiritual and political matters.

The separation between East and West also fostered distinct theological and ecclesiastical developments. In the West, the growing authority of the pope as the successor of Peter became a defining feature, with increasing emphasis on centralized governance. In contrast, the East continued to prioritize conciliar governance, where decisions were made collectively by bishops and councils, reflecting its theological and cultural traditions. Over time, these differences contributed to the growing divergence between the two branches of Christendom.

The loss of Jerusalem, Alexandria, and Antioch also planted the seeds of the Crusades. These cities, deeply significant to Christian faith and history, became a focal point of longing and inspiration for Western Christendom. The desire to reclaim these sacred sites from Islamic control grew steadily, eventually giving rise to the military campaigns of the Crusades. This division of Christendom into Eastern and Western spheres profoundly shaped the church's trajectory, influencing its theology, mission, and relationship with the broader world for centuries to come.

Conclusion

The Islamic conquest of the eastern patriarchates and the resulting bipolarity of Christendom is a sobering chapter in church history. It highlights the fragility of human institutions, even those tied to the faith, and the resilience of the church under Christ's promise that "the gates of hell shall not prevail against it" (Matthew 16:18).

While these events reshaped the leadership of the church and deepened divisions between East and West, they also remind us of the church's global nature and its dependence on Christ as its true head. From a Protestant evangelical perspective, this history underscores the importance of unity grounded in the gospel rather than political or cultural power.

As we reflect on this period, let us commit to the task of proclaiming the unchanging truth of Christ in a divided and changing world, trusting that His purposes will prevail in every generation.

Questions for Reflection

1. The rapid expansion of Islam resulted in the loss of three key Christian patriarchates: Jerusalem, Alexandria, and Antioch. How can this history remind us of the importance of holding to the gospel’s unchanging truth, even in the face of cultural and political shifts (Matthew 16:18)?
2. The division of Christendom into Eastern and Western spheres after the Islamic conquests led to theological and cultural divergences that would culminate in the Great Schism. How can Christians today work toward unity that honors both cultural diversity and the centrality of the gospel (John 17:20–23)?
3. Islamic expansion highlighted the vulnerabilities of divided Christian communities, particularly in regions affected by theological disputes such as the Monophysite controversy. What lessons can we draw from this about the need for clarity and unity in doctrine to face external challenges (1 Corinthians 1:10)?
4. The actions of missionaries and leaders like Charles Martel at the Battle of Tours preserved Christian Europe during this turbulent era. How can we draw courage and inspiration from their perseverance to stand firm in our faith amid contemporary challenges (Ephesians 6:10–13)?
5. The separation of the Eastern and Western churches shaped distinct theological and governance traditions, such as Rome’s emphasis on centralized papal authority and Constantinople’s conciliar approach. How can we critically engage with these historical developments while remaining focused on Christ as the true head of the church (Colossians 1:18)?

Resources

Bruce L. Shelley, Church History in Plain Language (Nashville: Thomas Nelson, 1995).

Justo L. González, The Story of Christianity, Vol. 1: The Early Church to the Dawn of the Reformation (New York: HarperCollins, 1984).

B.K. Kuiper, The Church in History (Grand Rapids:L Wm. B. Eerdmans Publishing Company, 2001).

Unless otherwise indicated, all Scripture quotations are from The ESV® Bible (The Holy Bible, English Standard Version®), © 2001 by Crossway, a publishing ministry of Good News Publishers. Used by permission. All rights reserved.