The evangelizing brothers Cyril and Methodius create the Cyrillic alphabet used in modern Slavic languages.

At issue in the Photian Schism, a four-year break between the episcopal sees of Rome and Constantinople, is not accusations of heresy but rather the papal claim to jurisdiction in the East.

The schism arises largely as a struggle for ecclesiastical control of the southern Balkans and because of a personality clash between the heads of the two sees, both of whom are elected in the same year (858) and both of whose reigns end in 867, by death in the case of the Pope, by the first of two depositions for the Patriarch.

The Photian Schism thus differs from what will occur in the eleventh century, when the pope's authority as a first among equals is challenged on the grounds of having lost that authority through heresy.

Eastern Southeast Europe (856–867 CE): Ecclesiastical Schism and Military Challenges

Settlement and Migration Patterns

Stability Amid Ecclesiastical and Military Tensions

From 856 to 867 CE, Eastern Southeast Europe experienced demographic stability, even as the region was influenced by significant religious and military events. Settlements continued consolidating, maintaining cohesion despite broader geopolitical tensions.

Political and Military Developments

Rus'-Byzantine Conflict (860 CE)

The period witnessed the significant Rus'-Byzantine War of 860, the only major recorded military expedition of the Rus' Khaganate in Byzantine and Western European sources. The Rus', taking advantage of Byzantine preoccupation with Arab conflicts, launched a surprise attack on Constantinople. Although the exact outcome remains unclear, Byzantine sources indicate a retreat by the Rus', attributed in later tradition to miraculous intervention by the Theotokos, thus enhancing religious sentiment and historical narrative.

Economic and Technological Developments

Economic Resilience Amid External Threats

Despite the military disruptions, the regional economy remained resilient, supported by stable trade networks and fortified infrastructure. Strategic fortifications continued to play a crucial role in protecting economic interests from external threats.

Ongoing Fortification Efforts

Continued enhancements in military fortifications, particularly around Constantinople and frontier areas, ensured regional stability and protection against sudden military incursions, such as the Rus' attack.

Cultural and Artistic Developments

Continued Cultural Flourishing

Cultural and artistic endeavors continued to thrive, supported by regional stability and institutional resilience. Despite external pressures, Byzantine cultural revival continued to advance scholarly and literary production, fostering cultural continuity.

Scholarly Persistence

Educational institutions and scholarly communities maintained active roles in preserving and promoting classical and theological traditions, further enriching regional cultural identity and intellectual resilience.

Social and Religious Developments

The Photian Schism

The prominent ecclesiastical event during this era was the Photian Schism, a four-year rupture between the episcopal sees of Rome and Constantinople. The schism arose primarily from disputes over ecclesiastical jurisdiction in the southern Balkans and was intensified by personal conflicts between Pope Nicholas I and Patriarch Photios, both elected in 858. Unlike later disputes, the Photian Schism centered around jurisdictional authority rather than accusations of heresy, significantly shaping ecclesiastical politics and relations between East and West.

Strengthening of Religious Institutions

Despite the schism, Eastern Orthodox institutions continued playing a central role in societal cohesion, influencing social and religious practices throughout the period. This ecclesiastical resilience reinforced regional stability and community identity.

Long-Term Consequences and Historical Significance

The era from 856 to 867 CE was defined by significant religious and military events, notably the Photian Schism and the Rus' military expedition against Constantinople. These developments critically shaped ecclesiastical politics, regional military strategy, and the religious-cultural identity of Eastern Southeast Europe, leaving enduring historical impacts.

The Rus'-Byzantine War of 860 is the only major military expedition of the Rus' Khaganate recorded in Byzantine and Western European sources.

Accounts vary regarding the events that took place, with discrepancies between contemporary and later sources, and the exact outcome is unknown.

It is known from Byzantine sources that the Rus' caught Constantinople unprepared, when the empire was occupied by the ongoing Byzantine-Arab Wars and unable to deal with the Rus' threat.

After pillaging the suburbs of the imperial capital, the Rus' retreat, although the nature of this withdrawal, and indeed which side had been victorious, is subject to debate.

This event gives rise to a later Orthodox Christian tradition, which ascribes the deliverance of Constantinople to a miraculous intervention by the Theotokos.

The Middle East: 856–867 CE

Catastrophe and Political Anarchy under the Abbasids

This era is marked by two dramatic events, both deeply impactful for the Abbasid Caliphate and the broader region.

The 856 Damghan Earthquake

On December 22, 856, one of the most devastating earthquakes in recorded history—the Damghan Earthquake (also known as the Qumis Earthquake)—strikes northeastern Persia. With an estimated magnitude of 7.9 and a maximum intensity of X (Extreme) on the Mercalli scale, this disaster devastates an area stretching some 350 kilometers (approximately 220 miles) along the southern edge of the eastern Alborz Mountains, affecting regions such as Tabaristan and Gorgan. Its epicenter is near Damghan, then the provincial capital of Qumis.

The earthquake causes catastrophic destruction, resulting in approximately 200,000 deaths, making it one of the deadliest earthquakes in world history. The physical and economic infrastructure of the region is severely damaged, significantly impacting local populations for generations.

The Anarchy at Samarra (861–870)

Meanwhile, the Abbasid Caliphate itself plunges deeper into political turmoil during a period historians later call the Anarchy at Samarra (861–870). Following the assassination of Caliph al-Mutawakkil in 861, a rapid and violent succession of caliphs reflects severe internal instability and the dangerous dominance of rival military factions, particularly powerful Turkish guards.

Caliph al-Muntasir briefly rules for six months before dying under suspicious circumstances, possibly poisoned by the Turkish commanders who had earlier supported him. His successor, al-Musta'in, attempts to assert independence but is quickly caught between factions of Turkish military elites. In 865, as divisions within the Turkish ranks become evident, al-Musta'in flees to Baghdad with some Turkish and Tahirid support. However, another faction of the Turkish army in Samarra selects al-Mu'tazz as a rival caliph, and the ensuing siege of Baghdad forces al-Musta'in's surrender and subsequent execution in 866.

This turmoil vividly illustrates the declining central power of the Abbasid caliphs, who increasingly become puppets controlled by military commanders. It signifies a critical shift in Abbasid political fortunes, demonstrating the vulnerability and fragmentation within the empire's heartland, and sets the stage for further decentralization and the rise of autonomous regional powers.

The 856 Damghan Earthquake, or the 856 Qumis earthquake, occurs on December 22, 856.

The earthquake has an estimated magnitude of 7.9, and a maximum intensity of X (intense) on the Mercalli intensity scale.

The meizoseismal area (area of maximum damage) extends for about three hundred and fifty kilometers (two hundred and twenty miles) along the southern edge of the eastern Alborz Mountains of present-day Iran, including parts of Tabaristan and Gorgan.

The earthquake's epicenter is estimated to be close to the city of Damghan, which is at this time the capital of the Persian province of Qumis.

It causes approximately two hundred thousand deaths and is listed by the USGS as the sixth deadliest earthquake in recorded history.

The term "Anarchy at Samarra" refers to the period in the history of the Abbasid Caliphate from 861 to 870, which is marked by extreme internal instability and the violent succession of four caliphs, who become puppets in the hands of powerful rival military groups.

The term derives from the capital and seat of the caliphal court, Samarra.

The "anarchy" begins in 861 with the murder of Caliph al-Mutawakkil by his Turkish guards.

His successor, al-Muntasir, rules for six months before his death, possibly poisoned by the Turkish military chiefs.

He is succeeded by al-Musta'in.

Divisions within the Turkish military leadership in 865 enable Musta'in to flee to Baghdad with the support of some Turkish chiefs and the Tahirids, but the rest of the Turkish army chooses a new caliph in the person of al-Mu'tazz and in 866 besieges Baghdad, forcing the city's capitulation.

Musta'in is exiled and executed.

Mediterranean Southwest Europe (856–867 CE): Muladi and Mozarab Revolts, and Umayyad Instability

The era 856–867 CE in Mediterranean Southwest Europe is characterized by significant internal unrest in Al-Andalus under Emir Muhammad I, involving revolts by Muladi and Mozarab populations, and continuing complex relationships among Iberian political entities.

Muladi and Mozarab Revolts under Muhammad I

The reign of Córdoba-born Umayyad Emir Muhammad I (r. 852–886 CE) is marked by widespread revolts among the Muladi (Muslims of ethnic Iberian origin) and Mozarabs (Christians living in Muslim-majority areas). Dissatisfied with the central authority, these groups express their discontent through numerous uprisings, reflecting the ongoing ethnic and religious tensions within Al-Andalus.

Musa ibn Musa and the Banu Qasi Revolt

Prominent among the rebels are the Banu Qasi, a powerful Muladi family led by Musa ibn Musa, governor of Zaragoza. Musa notably allies with the Arista family, rulers of the neighboring Christian Kingdom of Navarre, openly defying Córdoba’s authority. He audaciously proclaims himself the "third king of Spain," challenging both Emir Muhammad I of Córdoba and King Ordoño I of Asturias, illustrating the complex interplay of alliances and rivalries across religious and political boundaries.

Lucena and Jewish Cultural Influence

Meanwhile, Lucena continues to thrive as the cultural center of Andalusian Jewry, recognized for its unique all-Jewish character during the Muslim period. Jewish communities, particularly in Lucena, maintain significant roles in scholarship, commerce, and intercultural exchange, contributing greatly to the rich cultural tapestry of Al-Andalus.

Continued Carolingian Fragmentation and Italian Stability

In Italy, the Carolingian political landscape remains fragmented following the Treaty of Verdun (843 CE), though relative stability endures in territories ruled by Lothair I and his successors. The papacy sustains its central role as a stabilizing influence, fostering cultural continuity and maintaining diplomatic connections across fragmented Carolingian territories.

Economic and Technological Continuity

Technological developments, notably the widespread use of the Catalan forge, continue to underpin regional economic stability. Enhanced iron production supports improvements in agriculture, military capacity, and urban development, further sustaining prosperity and growth across Mediterranean Southwest Europe.

Legacy of the Era

The era 856–867 CE highlights critical ethnic, religious, and political tensions within Al-Andalus, marked by Muladi and Mozarab revolts against Umayyad rule. Simultaneously, the region's ongoing cultural vibrancy and economic stability continue to shape its dynamic medieval trajectory.

Several revolts and separatists movements of the Muladi (Muslims of ethnic Iberian origin) and Mozarabs (Christians living in the Muslim-majority areas) mark the reign of Cordoba-born Umayyad Emir Muhammad I.

The Banu Qasi Muladi family, led by Musa ibn Musa, the governor of Zaragoza, had allied with the Arista family of the Kingdom of Navarre, rebels, proclaiming himself "third king of Spain" (after Muhammad and Ordoño I of Asturias).

North Africa (856–867 CE)

Aghlabid Peak, Idrisid Challenges, and Sustained Autonomy

Between 856 and 867 CE, North Africa remains characterized by regional dynamism, economic vitality, and evolving political landscapes under powerful regional dynasties and independent entities.

In Ifriqiya, the Aghlabid Dynasty reaches a new height of influence. Under Ahmad ibn Muhammad (856–863 CE), governance from the capital Kairouan (Al Qayrawan) continues to emphasize infrastructural investments, fostering enhanced agricultural productivity and expansive trade networks. Ahmad ibn Muhammad's reign notably sees further expansion of Aghlabid influence in Sicily, cementing the dynasty’s status as a formidable Mediterranean maritime power.

Meanwhile, in Morocco, the Idrisid Dynasty faces emerging internal challenges and external pressures, which begin to gradually erode its previously robust authority. Despite this, Fez remains a significant cultural, commercial, and intellectual hub, preserving its reputation as one of the Maghreb's preeminent urban centers. The Idrisid rulers sustain an atmosphere of learning and commerce, even as their political control begins to experience fragmentation.

The Ibadi Rustamid Dynasty, headquartered in Tahert (modern Tiaret), continues its prominent role as a center for religious scholarship, intellectual freedom, and regional trade. The Rustamids' emphasis on tolerance and stability attracts merchants, artisans, and scholars, sustaining the economic and cultural importance of the dynasty.

Autonomous states also flourish during this period. The Emirate of Nekor maintains its prosperous position in northern Morocco, benefiting from Mediterranean trade routes linking the region to Umayyad al-Andalus. Simultaneously, the Barghawata confederation along Morocco's Atlantic coast continues to reinforce its unique religious and cultural identity, thriving independently of centralized control.

Additionally, Sijilmasa, centrally located in the Saharan region and managed by powerful Tuareg tribes, further solidifies its role as a crucial trans-Saharan trading center, connecting sub-Saharan Africa with Mediterranean commerce through the exchange of gold, salt, slaves, and goods.

By the conclusion of 867 CE, North Africa’s complex landscape remains vibrant and diverse, marked by continued Aghlabid strength, challenges within the Idrisid state, and enduring independent Berber polities, setting the stage for subsequent political and cultural shifts.