The Shia-Sunni Split and Its Impact on U.S. National Security
This paper examines the historical and theological origins of the Shia-Sunni divide within Islam, tracing the split from the death of the Prophet Muhammad in 632 CE through the Battle of Karbala and into the modern era. It describes the geographic distribution of each denomination, outlines core doctrinal differences, and analyzes how centuries of sectarian tension escalated into geopolitical conflict across the Middle East. The paper then focuses on how this ongoing divide — through events such as the Iranian Revolution, the Iran-Iraq War, the Gulf War, the U.S. invasions of Afghanistan and Iraq, and the rise of ISIS — has directly shaped U.S. foreign policy decisions and posed persistent challenges to American national security.
- Introduction: Islam's Two Primary Denominations: Demographics and doctrinal overview of Sunni and Shia Islam
- The Historic Denominational Split: Origins of the split after Muhammad's death in 632
- Sectarian Violence and Geopolitical Power Struggles: Definition and roots of Sunni-Shia sectarian conflict
- The Iranian Revolution and Its Aftermath: Shiite quietism, Pahlavi's coup, and Khomeini's rise
- U.S. Military Involvement and Escalating Sectarian Conflict: Gulf War, 9/11, Iraq invasion, and insurgency
- The Syrian Civil War and ISIS: ISIS advance, Sunni displacement, and Shiite militia retaliation
- Conclusion: Ongoing Implications for U.S. National Security: Persistent sectarian tensions and dilemmas for U.S. strategy
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What makes this paper effective
- Provides solid historical grounding before moving to contemporary geopolitical analysis, giving readers the context needed to understand modern conflicts.
- Draws a clear causal thread from the 7th-century theological split to 21st-century U.S. military decisions, making abstract religious history tangible and relevant.
- Uses specific named events, dates, and actors (Battle of Karbala, Ayatollah Khomeini, Saddam Hussein, ISIS) to anchor general claims in concrete historical fact.
Key academic technique demonstrated
The paper demonstrates effective chronological scaffolding — it builds an argument across time by sequencing causes and effects, showing how each political and military development emerged from prior sectarian tensions. This technique helps readers track the compounding nature of the conflict rather than treating individual events in isolation.
Structure breakdown
The paper opens with a demographic and doctrinal overview of Sunni and Shia Islam, then reconstructs the 7th-century origins of the split. A long central section traces political and military escalation from World War I through the post-2003 Iraqi insurgency. The final sections examine the Syrian Civil War, ISIS, and the dilemma facing U.S. and Iraqi forces trying to stabilize a region where Sunni communities fear both ISIS and Shiite militias. The conclusion implicitly frames the sectarian divide as an ongoing U.S. national security concern.
Introduction: Islam's Two Primary Denominations
Many religions have different denominations, and Islam is no exception. The two primary denominations of Islam are Sunni Islam and Shia Islam. The majority of Muslims across the globe are Sunni, estimated at roughly 85% to 90% of the global Muslim population. The remaining smaller share — approximately 15% — are Shia. Further distinctions indicate that most Shias belong to the tradition known as Twelver, with the rest of the Shia identifying with other traditions.
"Twelver" refers to the number of descendants of Muhammad that this sect of the Shia recognize as legitimate successors. Another group is referred to as the Seveners, since they recognize only seven descendants who were official caliphs of Islam. This is further complicated by the concept of Occultation, which refers to a messianic figure — the Mahdi — who is born but goes into hiding in order to remain safe. Critics have described the concept of Occultation as a pious fraud that promotes the idea of waiting faithfully for a messiah who will renovate the world by eradicating evil and restoring justice. Moreover, a period of Occultation permits an elaborate system of communication between believers and agents of the Mahdi, as only certain privileged individuals are believed to be capable of conducting the sacred duty of contacting the hidden Mahdi on behalf of the faithful. In this scenario, the Mahdi is said to be physically present but in hiding. In other scenarios, no one presides over the Shia faithful, who all await the Mahdi's return. An objective scholar can readily see the possibilities for controlling communities of believers without authentic authority to do so.
In any given Muslim community, Sunnis tend to be in the majority. This is true for Muslim communities across most of the Arab world and in Africa, China, South Asia, and Southeast Asia. Globally, the largest number of practicing adherents of the Sunni tradition reside in Indonesia. The Shia, on the other hand, constitute the majority of Muslim populations in Azerbaijan, Bahrain, Lebanon, Iran, and Iraq. The largest population of Shia Muslims is found in Iran. Pakistan occupies a unique position as the country with both the second-largest Sunni population and the second-largest Shia Muslim population in the world.
The Historic Denominational Split
The death of a religious leader is a vulnerable time for believers and for the religion as an institution. When Muhammad, the Prophet of Islam, died in 632 CE, the response of believers was chaotic, as a caliph to succeed him had not been designated. That Muhammad was a prophet who possessed special knowledge of the Quran and professed direct communion with God (Allah) made him fundamentally irreplaceable. Muslim believers stood at a precipice as it became clear that their prophet was dying. Muslim elders in Medina agreed to designate Abu Bakr as caliph, thereby addressing the urgent need for a successor. Abu Bakr was the father-in-law of the Prophet Muhammad. By selecting Abu Bakr, the elders established a precedent that future caliphs would be members of the Quraysh tribe. A minority of elders, however, favored a man named Ali, and called themselves Shiat Ali — the partisans of Ali. In 656 CE, following the assassination of his predecessor, Ali became the fourth caliph, and subsequent rebellion against him arose among some Muslims.
A growing dispute escalated into the Battle of Siffin, a conflict pivotal to the shift from argument and disagreement to full-scale violence. What soon followed was the even larger Battle of Karbala in 680 CE, in which Hussein ibn Ali, the son of Ali, marched against the caliph's army in Iraq. Hussein's army was massacred, and he and his entire household were killed at the hands of the Umayyad Caliph Yazid I. The divide between the Shiites and the Sunnis deepened irreparably.
What began as an ideological schism and a struggle for political power deteriorated into revenge-seeking and an irreparable breach between the Sunni and the Shia. As the two denominations continued to mature separately from one another, differences in beliefs, customs, traditions, and religious practices emerged. While all Muslim groups regard the Quran as divine, disputes about jurisprudence and the hadith have created strong separations among the denominations of Islam. Hadith refers to the process of attribution that accompanies secondary interpretations of a divine text — a process that necessarily follows as believers strive to align what they understand of the Quran with what they know Muhammad said, what they believe he said, and what they believe he tacitly approved or sanctioned.
Sectarian Violence and Geopolitical Power Struggles
Over many centuries, relations between the Sunni and the Shia have been alternately cooperative or hostile, depending largely on substantive political events within Muslim-majority countries. Sectarian violence is the term for conflict and strife inspired by differences in ideology or religion among different sects within a larger community or nation. It is a particularly apt term for the conflict that has persisted between Sunni and Shia throughout the Middle East. A series of epic power struggles and international conflicts has intensified sectarian violence among Islamic sects.
Conclusion: Ongoing Implications for U.S. National Security
American, Kurdish, and Iraqi forces have worked to drive out the Islamic State (ISIS/ISIL), with hopes of eliminating them from Iraq altogether. Yet the Shiite and Sunni communities impacted by these forces remember all too well the 2006–2008 civil war, the violence against the Sunnis from 2010 to 2014, and the apparent acceptance of the Islamic State by some Sunnis during that period. As Shiite military units move further into Sunni territory to force out ISIS, Sunni villagers and farmers fear for their lives. The danger this presents for both the United States and the Iraqi army is that Sunnis may choose to align with the Islamic State as the perceived lesser of two evils — a strategic calculation that would severely complicate efforts to achieve lasting stability in the region and protect American national security interests.
References
Caliphate. (2015). In Encyclopaedia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/89739/Caliphate
Hendawi, H., Abdul-Zahra, Q., and Yacoub, S.N. (2015, January 6). In Iraq's war against extremists, a quiet sectarian purge. AP. Retrieved from
Hazleton, L. (2010). After the prophet: The epic story of the Shia-Sunni split in Islam. Aylett, VA: Anchor.
Pollack, K.M. (2015, February 4). ISIS is losing in Iraq. But what happens next? The New York Times, p. A25.
Shuster, M. (2007, February 12). Chronology: A history of the Shiite-Sunni split. National Public Radio (NPR). Retrieved from http://www.npr.org/2007/02/12/7280905/chronology-a-history-of-the-shia-sunni-split
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