The theological split is real and old, but the idea of 1,400 years of nonstop sectarian war doesn’t survive a look at the evidence.
Key Takeaways
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The Sunni and Shia traditions trace their split to a dispute over who should lead the Muslim community after the Prophet Muhammad died in 632 CE.
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For most of the following thirteen centuries, Sunni-Shia identity was rarely the main reason people in the region went to war.
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The 16th-century rivalry between the Ottoman and Safavid empires is the strongest historical case of empire and sect fusing into political conflict.
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Many historians trace today’s sectarian tensions mainly to modern events, especially the 1979 Iranian Revolution, the Saudi-Iran rivalry, and the 2003 invasion of Iraq.
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Calling the conflict “ancient” can make it seem permanent, while scholars who stress its political roots see it as something that can change.
Introduction
When the Middle East makes the news, commentators often offer the Sunni vs. Shia divide as the explanation. Commentators describe a feud stretching back to the seventh century, as if Sunni and Shia Muslims have been fighting without pause since the Prophet Muhammad’s death. In this telling, the region’s wars are simply the latest round of a religious struggle that can never end.
The split itself is real, and it does go back nearly fourteen centuries. Sunni and Shia Muslims differ on early leadership, religious authority, and some practices, and those differences matter deeply to believers. What the “ancient hatred” story leaves out is everything in between: centuries of coexistence, shared cities, intermarriage, and conflicts driven by land, trade, and dynastic ambition.
This article examines Sunni and Shia history from several perspectives. It explains how each tradition understands the original split, examines the long periods that don’t fit the conflict narrative, and weighs the strongest evidence on both sides of the debate about why sectarian tension rose so sharply in recent decades.
Where the Sunni-Shia Split Began
The Sunni-Shia split began with a question of leadership after the Prophet Muhammad’s death in 632 CE. Those who became known as Sunnis accepted the community’s choice of Abu Bakr as the first caliph, or successor. Those who became known as Shia hold that leadership belonged to Ali, the Prophet’s cousin and son-in-law, and his descendants.
Each tradition tells this story in its own way. In the Sunni view, the community chose the first four caliphs, including Ali, as rightly guided leaders. In the Shia view, the Prophet designated Ali as his successor, and authority should have passed through a line of imams from his family. The term “Shia” derives from “shi’at Ali,” which means “the party of Ali.”
A defining moment came in 680 CE at Karbala, in present-day Iraq, where Ali’s son Husayn and a small group of companions were killed by forces of the Umayyad caliph. Shia Muslims commemorate Husayn’s death each year on Ashura as a central act of mourning and devotion. Many Sunnis also honor Husayn, though Ashura carries different meanings in the two traditions.
Over the following centuries, the two traditions developed distinct schools of law, theology, and religious authority. Today Sunnis make up a large majority of the world’s Muslims, while Shia Muslims form majorities in Iran, Iraq, Bahrain, and Azerbaijan and significant communities in Lebanon, Pakistan, Yemen, and the Gulf.
Thirteen Centuries That Don’t Fit the “Ancient Hatred” Story
The “ancient hatred” framing skips over most of Islamic history. Between Karbala and the late 20th century, Sunni and Shia Muslims fought plenty of wars, but usually over power, territory, and trade rather than sect. Shia dynasties ruled Sunni-majority lands, and Sunni rulers governed Shia populations, often without sect being the defining issue.
Consider a few examples. The Fatimid dynasty, which followed the Ismaili branch of Shia Islam, ruled Egypt from 909 to 1171 over a largely Sunni population and founded Cairo’s al-Azhar. In the 10th and 11th centuries, the Shia Buyid family controlled Baghdad while the Sunni Abbasid caliph remained on his throne. And until about 1500, Iran itself was majority Sunni.
The historian John McHugo, author of A Concise History of Sunnis and Shi’is, has argued that the image of a centuries-old sectarian war is neither accurate nor helpful. In an interview with The New Arab, he traced the West’s focus on the sectarian lens largely to the Iranian Revolution of 1979.
There were real moments of sectarian violence and persecution in these centuries, and historians do not pretend otherwise. The point is proportion: those episodes sit among long stretches in which sect was one identity among many, alongside city, tribe, language, profession, and dynasty.
EVIDENCE CHECK: The popular claim is that Sunnis and Shia have been at war since the seventh century. The record shows long periods of shared rule and coexistence, including Shia dynasties governing Sunni-majority Egypt and Baghdad. As late as 1959, al-Azhar’s leading scholar, Mahmud Shaltut, issued a ruling recognizing the main Shia school of law as valid for Muslims to follow.
The Safavid-Ottoman Rivalry: When Empire and Sect Fused
The strongest historical case for a Sunni vs. Shia conflict comes from the 16th century. When Shah Ismail founded the Safavid dynasty in 1501, he made Twelver Shia Islam the official religion of Iran. The neighboring Ottoman Empire, which presented itself as the leading Sunni power, saw the new state as both a military and religious threat.
The two empires went to war repeatedly. At the Battle of Chaldiran in 1514, the Ottoman Sultan Selim I defeated Ismail’s army and briefly took the Safavid capital, Tabriz. The Ottomans also harshly suppressed Shia-leaning Turkmen communities in Anatolia who sympathized with the Safavids, while the Safavids pressured Iran’s Sunni population to convert.
This is the period that supports the continuity argument. Some writers see the Ottoman-Safavid rivalry as a direct ancestor of today’s tensions between Iran and its Sunni-majority neighbors.
Other historians stress how much of the rivalry was about territory and trade routes and how often it ended in negotiated borders. The Peace of Amasya in 1555 and the Treaty of Zuhab in 1639 set frontiers that still roughly mark the line between Iran and its western neighbors. In this reading, sect was a powerful tool of legitimacy for two empires competing over the same lands, rather than the root cause of their wars.
1979 and the Making of Modern Sectarianism
Many scholars identify 1979 as the turning point for modern Sunni-Shia tension. That year brought the Iranian Revolution, which created a state openly committed to exporting its revolutionary Shia model, along with the armed seizure of Mecca’s Grand Mosque and the Soviet invasion of Afghanistan. Together, these events reshaped religious politics across the region.
The journalist Kim Ghattas makes this case in her book Black Wave. As a CIA Studies in Intelligence review summarizes it, she argues that before 1979 Sunnis and Shia largely lived side by side, and that the rivalry between Saudi Arabia and Iran that followed revived old grievances and invented new ones.
Academic researchers have reached similar conclusions. In a Tufts University profile, Satgin Hamrah, editor of Contextualizing Sectarianism in the Middle East and South Asia, argued that sectarian conflict grows mainly out of the region’s recent political history rather than ancient hatred. One of her contributors, Pouya Alimagham, points out that before 1979, Saudi Arabia and Iran cooperated on a military mission in Oman and kept cordial relations.
Before 1979, Sunni Saudi Arabia and Shia Iran were partners in a military mission in Oman.
Critics of this view caution against overcorrecting. Religious identity was not invented in 1979, and theological disagreements have long shaped how communities see each other. The more careful version of the argument is that modern states and movements took a real religious difference and turned it into a tool of political mobilization.
Iraq, Syria, and the Politics of Identity After 2003
The 2003 invasion of Iraq marked the second major turning point. The fall of Saddam Hussein’s government ended a long period in which Iraq’s Sunni Arab minority dominated the state, and the new political order distributed power largely along sectarian and ethnic lines. Within a few years, Sunni and Shia militias were targeting civilians, as the Council on Foreign Relations timeline of the period documents.
The Syrian civil war that began in 2011 deepened these divides. The rise of the Islamic State group, which presented itself as a defender of Sunnis and treated Shia Muslims as enemies, was met by Iranian-backed Shia militias. An analysis from the Arab Center in Washington, DC, argues that this cycle reflects the failure of state-building and foreign intervention more than theology and warns that in such conditions people can begin to identify more as Sunni or Shia than as Iraqis or Syrians.
Iraqis who lived through this period often describe how quickly things changed. Mixed neighborhoods and Sunni-Shia marriages had been common in Baghdad, and many families included members of both communities. The violence that followed 2003 was real and devastating, but it was not the natural state of Iraqi society.
EVIDENCE CHECK: The common assumption is that sectarian war in Iraq after 2003 simply released hatreds that had always been there. Historians and Iraqis themselves point to a different record: decades of mixed neighborhoods and intermarriage before the war, followed by a political system, an insurgency, and outside powers that made sect the main currency of power.
Sunni vs. Shia Today: Faith, Politics, and Daily Life
For most Sunni and Shia Muslims today, the difference shows up in practice and religious authority far more than in conflict. Shia communities follow senior religious scholars, known as marjas, and observe Ashura and pilgrimages to shrines such as Karbala and Najaf. Sunni communities follow one of four main schools of law and lack a comparable clerical hierarchy.
At the same time, there have been repeated efforts at bridge-building. In 2004 and 2005, the Amman Message, an initiative launched in Jordan and endorsed by hundreds of scholars from both traditions, affirmed the legitimacy of the major Sunni and Shia schools of law. Dialogue between Sunni and Shia religious institutions continues, even as political rivalries rise and fall.
The political map is also shifting. Saudi Arabia and Iran restored diplomatic relations in 2023 after a seven-year break, a reminder that state rivalries, unlike theology, can change quickly. Whether tensions rise or ease often depends less on doctrine than on wars, alliances, and the strategies of governments.
Why It Still Matters
How we describe the Sunni-Shia divide shapes how we think about the region’s future. If the conflict is “ancient” and religious, it sounds permanent, and outsiders can dismiss it as unsolvable. If it is largely political and modern, it becomes something that leaders, institutions, and ordinary people can change.
The evidence does not support either extreme. Theology matters, and the split has shaped Muslim history for fourteen centuries. But most of that history was not war, and the sharpest sectarian conflicts of our era grew out of revolutions, invasions, and state rivalries that are only decades old. Reading the news with that background makes it easier to ask the right question: not “Why do they hate each other?” but Who benefits from turning a religious difference into a political battle line?.
Frequently Asked Questions
What is the main difference between Sunni and Shia Muslims?
The split began over who should lead the Muslim community after the Prophet Muhammad died in 632 CE. Sunnis accepted the community’s choice of Abu Bakr as caliph, while Shia Muslims believe leadership belonged to Ali and his descendants. Over time the traditions developed different schools of law, practices, and structures of religious authority.
Have Sunnis and Shia always been at war?
No. There were episodes of sectarian violence, but for most of Islamic history Sunni and Shia communities coexisted, and wars were usually fought over power and territory. Shia dynasties ruled Sunni-majority regions such as Fatimid Egypt, and Iran was mostly Sunni until about 1500.
What happened at the Battle of Karbala?
In 680 CE, Husayn, the grandson of the Prophet Muhammad, was killed at Karbala in present-day Iraq along with a small group of followers by the forces of the Umayyad caliph. Shia Muslims mark his death each year on Ashura, and the event is central to Shia religious identity.
Why did Sunni-Shia tensions increase after 1979?
Many historians point to the 1979 Iranian Revolution, which created a state seeking to spread its revolutionary model, and the rivalry with Saudi Arabia that followed. Later events, especially the 2003 invasion of Iraq and the Syrian civil war, deepened sectarian divisions.
Which countries have Shia majorities?
Shia Muslims form majorities in Iran, Iraq, Bahrain, and Azerbaijan. Large Shia communities also live in Lebanon, Pakistan, Yemen, Saudi Arabia, Kuwait, and other countries.
Further Listening & Reading
To hear scholars discuss Islamic history, the Safavids, the Ottomans, and modern Iran in their own words, explore the Unraveling Middle East interview series, featuring more than 236 historians. For more of the history behind today’s headlines, visit the History Behind News program, and subscribe to the UME email list on the homepage to catch new interviews.
