Answer: The Salafi movement is a subset of Islam that applies Sharia Law according to a strict, originalist, and highly aggressive interpretation. Within the religion of Islam, there are several major denominations. By far, the largest of these is Sunni Islam, making up more than 75 percent of Muslims worldwide. Causing divisions within Sunni Islam are varied interpretations, or fiqh, on how to properly apply Islamic law. The four major “schools” of law, based on fiqh, are Hanafi, Maliki, Shafi’i, and Hanbali. One of several subsets within the Hanbali school is Wahhabi, and Salafi is a relatively recent interpretation of Wahhabism.

The Salafi movement is typically explained as a reaction to European dominance over Arabic lands. Over the first few centuries of its existence, the Islamic Empire conquered a vast territory. This extended as far as southern Europe before further conquest was stymied by the first Crusade. By comparison, Islamic power in the nineteenth century was slim, all but overrun by European colonialism. Angst over a lack of influence and the watering-down of Islamic practice gave rise to Wahhabism, which sought to return Islam to its earliest beliefs and most stringent applications of Shariah. This perspective was influential in the establishment of the nation now known as Saudi Arabia.

By the dawn of the twentieth century, the Wahhabist approach had developed into Salafism, or the Salafi movement. The distinctive belief of this group is that Islam has strayed from the beliefs and practices of Muhammad and his earliest followers. In particular, Salafis believe that Islam has been contaminated with non-Muslim ideas and practices. The Salafist intent is to return Islam to the same form that Muhammad left it in, without modern variations in doctrine or practice and with an uncompromising application of Sharia Law. Most Muslims within Salafism either reject politics entirely or believe in working through normal civic processes to change society. However, some Salafis believe that aggressive, violent jihad is a requirement of Islamic faith.

Interestingly, the same political and religious environment also spawned a group that espouses an almost pacifist mentality and was the first to act as Muslim “missionaries”: the Ahamadiyya sect.

Despite being an extremely narrow band of Islamic interpretation, jihadist Salafism is identified with almost every infamous Islamic terrorist organization. Such groups include ISIS, Boko Haram, and Al Qaeda. When Western news outlets speak of “Islamic fundamentalism” or “Islamic militants,” they very often mean Salafi Islam or one of its subsets. To clarify, parsing the beliefs of Muslims to arrive at this unique interpretation of Islam goes a full five layers deep: Islam ⊃ Sunni Islam ⊃ Hanbali School ⊃ Wahhabism ⊃ Salafism ⊃ Jihadist Salafism.

Salafism’s relatively large presence in Saudi Arabia—home to Islam’s holiest cities and considerable wealth—has contributed to its outsized influence in the modern world. This influence appears to be growing; unrest in the Middle East is partly responsible for the Salafi school being the fastest-growing interpretation of Islam worldwide.