When the militant forces of ISIS (the Islamic State of Iraq and Syria) recently occupied a large portion of the Middle East and declared the establishment of a new country under an Islamic caliph (leader), it became apparent to the outside world that much of the conflict involved Muslims fighting one another.

Specifically, the continuing conflict involves two major sects of Islam: Sunni (the sect of ISIS) and Shi’ite. This may prompt us to ask, “What’s the difference? Muslims are Muslims, aren’t they?”

Well, yes and no. Understanding the difference between Sunnis and Shi’ites may help us grasp the centuries-old animosity between these two major Islamic groups. But make no mistake: Sunnis and Shi’ites gladly set aside their differences when they can join together to destroy their common enemies – primarily Jews and Christians.

Muhammad’s successors

Muhammad founded Islam in the Seventh Century A.D. but named no successor. After his death in 632 A.D., Muslims became deeply divided on the issue of who should take up the mantle of leadership of this new religion.

By consensus, Muhammad’s followers selected his cousin Abu Bakr as the first caliph. After his death about a year later came the second caliph, Umar, who spread Islam into Syria and North Africa, and who drove Christians and Jews out of Arabia.

His assassination led to the rise of the third caliph, Uthman, a son-in-law of Muhammad, and then a fourth leader, Ali ibn Abi Talib, the husband of Muhammad’s daughter Fatima by his first wife Khadija. When his own soldiers murdered Ali, a fifth caliph, Mu’awiya, succeeded him.

But the caliphate began to unravel amidst disagreements that led to the Sunni / Shi’ite split.

Muslims who continued to believe that the leadership of Islam should be based on a consensus of the faithful came to be known as Sunnis, or traditionalists. Others, devoted to Ali, the murdered fourth caliph, insisted that all divinely inspired leaders of Islam, known as Imams, must be direct descendants through the line of Fatima. So, they declared Ali the first Imam and became known as the “Shia” or party of Ali.

In all, Shi’ites believe there have been twelve Imams, with the twelfth, Muhammad ibn al-Hasan, going into hiding in 874 A.D. So-called “Twelver” Shi’ites believe he is still alive and will return in the last days as the Mahdi or “The Guided One” who will lead the armies of Islam to final victory over the forces of Satan (especially Christians and Jews).

In some respects, Shi’ites regard the Mahdi in the same way Christians anticipate the return of Christ – with vastly different results, of course.

In short, Sunnis insist that the leadership of Islam should represent the consensus of Muslims around the world, while Shi’ites recognize as inspired leaders only the Imams whose bloodlines may be traced back to Muhammad through the line of Fatima.

Sunnis today account for more than 80 percent of Muslims worldwide.

Other differences

Besides leadership issues, Sunnis and Shi’ites differ in other ways.

Authority. Sunnis emphasize the authority of the written traditions, which include the Qur’an and the Sunna (“custom”), from which they derive their name. They also receive guidance from a consensus of elders (ulama), who base their decisions on Islam’s writings. Shi’ites look more toward human authority and, as mentioned above, “Twelvers” eagerly await the imminent return of the Mahdi.

Civil and religious power. Sunnis believe there should be a separation between civil and religious authorities, while Shi’ites believe the religious authorities should exercise both political and religious power. Ayatollah Khomeini, who led the Islamic revolution against the shah of Iran in 1979, was a Shi’ite leader.

There is another significant sect of Islam known as Sufism, which is mystical in nature. Minor sects include the Wahhabis (primarily in Saudi Arabia), the Druze (mostly in Lebanon, Syria and northern Israel), the Alawites (mainly in Syria), and the Ahmadiyas (primarily in Pakistan).

Beyond this, Islam has been influential in the founding of two other religions: Sikhism and Baha’i.

In the end, Sunnis and Shi’ites may be loosely compared to Roman Catholics and Protestants in Christianity. They agree on many theological issues but become divided in matters of religious leadership, authority, and practice – in some cases going to war over these issues.

All Muslims are unified, however, in their belief that Jews and Christians are kafirs, or infidels, who must be conquered, converted by persuasion or compulsion, subjugated, or eliminated. On this the Sunnis of ISIS and the Shi’ites of Iran are in full agreement.

This column first appeared August 26, 2014, in The Pathway, the news journal of the Missouri Baptist Convention.