Throughout history, religion has been a major source of conflict between groups of people. Wars with religious motivations or justifications have led to immense suffering and loss of life. Determining which religious war was the longest depends on how one defines and categorizes religious wars. By most accounts, the longest ongoing religious war has been between various Muslim sects, spanning over 1300 years from the 7th century up to modern times. However, Christendom also saw centuries of religious wars between Catholics and Protestants starting in the 16th century. The complex history and shifting alliances involved in these conflicts makes determining a precise length difficult. Nonetheless, the available evidence points to the Muslim sectarian conflicts as having the longest continuous duration of organized religious warfare.
Defining Religious Wars
To identify the longest religious war, we must first define what constitutes a religious war. Religious wars involve armed conflict between different religious groups, often but not always along sectarian lines within a religion. Throughout history and across religions, political, economic, and ethnic factors have often became intertwined with religious differences in fomenting conflict. Thus religious wars may have both religious and secular motivations. Additionally, the parties involved need not be officially organized religious institutions but can be identity groups defined by religious affiliation. Given these complexities, there is no uniformly accepted definition of religious wars. However, most scholars agree wars motivated to a substantial degree by theological disputes or sectarian hatred qualify as religious wars. With this expansive definition, both formal campaigns endorsed by religious authorities and prolonged internecine violence between religious groups can be considered religious wars.
Muslim Sectarian Conflicts
The longest series of related religious wars have been fought between various Muslim sects and factions over the course of Islamic history. Soon after the death of the Prophet Muhammad in 632 AD, disputes over rightful leadership led to the Split between Sunni and Shia Muslims. This initial schism evolved into a sectarian conflict that has persisted in various forms up to the present day. While exact tolls over 1300 years of disorganized violence are impossible to calculate, cumulative deaths from Muslim sectarian conflicts likely number in the millions. Let us survey some of the major episodes contributing to this tragic continuity of religious warfare within Islam.
First Fitna: 656-661 AD
The First Fitna was the initial civil war over leadership of the young Islamic empire. Following the assassination of the third caliph Uthman, Ali became caliph. This was contested by Muawiyah, the governor of Syria and kinsman of Uthman. Their forces met at the Battle of Siffin in 657. Muawiyah’s troops raised pages of the Quran on their lances as a plea for arbitration. Though Ali won the battle, he agreed to arbitration that ultimately undermined him. A Kharijite extremist group later assassinated Ali, and Muawiyah seized the Caliphate, establishing the Umayyad Dynasty. This conflict established the main schism between Sunni and Shia as well as the Kharijite sect.
Second Fitna: 680-692 AD
After Ali’s martyrdom at Siffin, his son Hussein became leader of the Shia. However, when Hussein attempted to regain the Caliphate in 680, he was defeat and killed along with much of the Prophet Muhammad’s family at the Battle of Karbala by the ruling Sunni Umayyad Caliph Yazid I. Hussein’s martyrdom helped solidify the nascent Shia identity and cause. Additionally, his death helped provoke the Second Fitna civil war which further weakened Umayyad control and credibility. This sectarian conflict created lasting schisms between Shia and Sunni branches.
Abbasid Revolution: 747-750 AD
The Abbasid Revolution overthrew the Umayyad Dynasty, ending Sunni Arab exclusivity and ushering in the ethnically inclusive Abbasid Caliphate. The Abbasids deliberately appealed to non-Arab Muslims, gaining support from Persians, Berbers and others by proposing a more egalitarian Islam. Though motivated more by politics than theology, this conflict had a sectarian dimension as the Umayyads represented narrow Sunnism while the Abbasids reflected more inclusive Islam. The Abbasid victory did not end sectarianism but did shift the contours of inter-Muslim conflicts.
Fatimid-Abbasid Wars: 893-1040 AD
The Fatimids were an Ismaili Shia dynasty claiming descent from Muhammad’s daughter Fatimah. They challenged the Baghdad-based Abbasids for control of the Caliphate. At the height of their power in the 10th century, the Fatimids controlled North Africa, the Levant, Hejaz and Yemen. The long series of wars between the two Caliphates combined sectarian, political and economic factors. Though Shia theology was important for Fatimid legitimacy, many of their subjects were Sunnis, indicating theology alone did not determine loyalties. Nonetheless, their powerful counter-Caliphate represented a direct religious challenge to Sunni Abbasid authority.
Crusades: 1095-1492 AD
The Crusades were a series of wars by European Christians to conquer and colonize the Middle East, justified by religious motives. Though primarily a Christian vs. Muslim conflict, the Crusades had a sectarian dimension within Islam. The Sunni Seljuk Turks had displaced the Shia Fatimids in controlling Jerusalem when the First Crusade arrived in 1099. Many local Muslims allied with the Crusaders against the Turks on the basis of shared enemies. Nur ad-Din and Saladin later united the region’s Sunnis against the Crusader states. The threat of Christian conquest encouraged cooperation among bickering Muslim factions. After expelling the Crusaders, Sunni Mamluk Egypt became the dominant Muslim power rather than Shia states like the Fatimids.
Safavid-Ottoman Wars: 1514-1746 AD
The Safavid Empire represented the emergence of Shia Islam as a state religion. The Safavids originated as a Sufi order but converged on militant Shia ideology by the 16th century, using it to unify Persia in opposition to the Sunni Ottoman Empire. Starting in 1514, the Ottoman-Safavid Wars were fought for control of eastern Turkey, Iraq, the Caucasus and Transoxiana. These territories contained intermixed Sunni and Shia populations, leading to nationalist and sectarian solidarities. The Safavids forcibly converted Persia to Twelver Shia Islam while the Ottomans championed Hanafi Sunni orthodoxy, making this a clear sectarian struggle for religious dominance. The 1555 Peace of Amasya recognized a rough sectarian division of territories between the two empires.
Wahhabi Movement: 1740s-Present
Wahhabism originated as a Sunni revivalist movement within the Arabian Peninsula, aimed at eradicating popular Islamic practices deemed heretical innovations. Led by preacher Ibn Abd al-Wahhab and Emir Muhammad bin Saud, Wahhabism gained political power by allying with the House of Saud in 1744. Wahhabi armies attacked Shia regions, destroying shrines and converting the population by force. Sectarian massacres occurred between Wahhabis and Shias in Karbala in 1801 and 1802. The Saudi-Wahhabi alliance continued leading armed uprisings against Ottoman rule. Though suppressed for a time, Wahhabism again grew powerful during the 20th century. Its resurgence has influenced jihadist groups like al-Qaeda and ISIS which declare Shias to be apostates.
Iran-Iraq War: 1980-1988 AD
This bloody war ostensibly fought over a territorial dispute also had a strong sectarian dimension. Iraq’s Saddam Hussein feared the 1979 Iranian Revolution could inspire Iraqi Shias who made up the majority of the population. Hussein thus repressed Shia organizations and tried to undermine Iran’s new Shia revolutionary regime led by Ayatollah Khomeini. Iran in turn encouraged Iraqi Shia dissent. Both sides exploited sectarian identities for nationalist goals in this war fueled by religious passions. Use of child soldiers by Iran also reflected religious radicalization. The war ended in stalemate after hundreds of thousands of deaths but no change in borders.
Catholic-Protestant Conflicts
While factional Muslim conflicts represent the longest continuous series of related religious wars, the Christian world also saw prolonged violent tensions between Catholics and emerging Protestant groups following the Reformation in 1517. ThesePost-Reformation wars over theology, power and resources left millions dead and lasted from the 1500s up until the early 1700s – over two centuries of intermittent religious warfare, though not continuous violence. Let us summarize some of the major Catholic-Protestant conflicts of this era.
The French Wars of Religion: 1562-1598
These civil wars in France pitted French Catholics against Protestants – mainly Calvinist Huguenots, the country’s Protestant minority. Religious mob violence precipitated more organized warfare. The 1572 Saint Bartholomew’s Day Massacre of Huguenots in Paris exemplified the scale of sectarian atrocities. Politically, the Huguenots allied with nobles seeking to weaken the French monarchy, while Catholics supported the crown. The fighting ended after Protestants were granted amnesty and religious freedoms by the Edict of Nantes in 1598, though turmoil resumed decades later.
The Thirty Years War: 1618-1648
This complex European war began as a religious conflict between Protestant and Catholic states within the Holy Roman Empire but expanded into a general continental power struggle. Triggers included Protestant-Catholic tensions in Bohemia and the struggle for political dominance within the Empire. Major powers like France and Sweden intervened for their own interests, turning the later stages of the war into a political rather than religious conflict. The Peace of Westphalia ended the war in 1648 on the basis of state sovereignty, establishing the principle of cuius regio, eius religio – states had the right to determine their own religions.
The English Civil Wars: 1638-1651
While politics and rights motivated the factions in the English Civil Wars, religious affiliations lined up with their stances. The Royalists and Anglicans largely backed King Charles I against the Parliamentarians, who were mostly Puritan. Disagreements over English Calvinism fueled the unrest, as did protests against Catholic-style practices reintroduced in the Anglican Church by Archbishop Laud. Parliamentarian leader Oliver Cromwell aggressively campaigned against Irish Catholics from 1649-1650, massacring garrisons and towns. In England, Anglican Royalism was briefly banned until the monarchy and Church were restored in 1660.
Later Catholic-Protestant Conflicts
Religious tensions lingered and sporadically reignited violence in France and Britain during the late 17th and early 18th century. In France, starting in the 1620s, Cardinal Richelieu sought to suppress Huguenot political influence and religious freedoms, reversing decades of tolerance. The infamous Siege of La Rochelle ended Huguenot military resistance. Louis XIV later revoked additional Protestant rights during the 1680s. In Britain, anti-Catholic paranoia drove the Popish Plot hysteria during the Exclusion Crisis in 1679-1681. Though these later conflicts did not escalate to full civil wars, they demonstrated lingering sectarian animosities.
Comparison
Based on this historical survey, while the Reformation sparked major religious wars in Europe during the 16th and 17th centuries, the level of ongoing violence appears less than that seen between Muslim sects over an even longer duration from the 7th century onwards. Catholic-Protestant conflicts were more confined in geography, duration and scale than the recurrent Muslim sectarian violence spanning multiple continents and historical periods. The shared Abrahamic origins yet theological divergences of Islam created durable schisms and animosities never fully settled within the Muslim world. Therefore, the accumulated evidence indicates the title of longest religious war belongs to the 1300 years of intermittent conflict between Muslim sectarian factions, even if peaceful periods intervened between major episodes of violence.
Conclusion
Identifying the longest religious war depends greatly on definitions and framing. By treating the accumulated conflicts between Muslim sects from the 7th century through today as part of a related historical continuity, the sectarian violence within Islam constitutes the longest running religious war. While Europe also experienced a few centuries of Catholic-Protestant conflict, these wars were more geographically bounded and discontinuous than the recurrent Muslim sectarian violence. The complex and shifting nature of religiously-tinged conflicts makes definitive labels difficult. However, the tragic story of intra-Muslim sectarian tensions fueling prolonged internecine conflict remains unparalleled in its duration and resilience throughout history. Hopefully understanding this painful legacy can help promote reform and reconciliation.