Until the nineteenth century, religion was usually the only acceptable justification of terror. It is not hard to understand why: religion gives its true believers an account of the good life and a way of recognizing evil; if you believe that evil in the form of wrong beliefs and mistaken customs weakens or corrupts a life ordained by God, you are under a profound obligation to combat that evil. If you enjoy the companionship of like-minded believers, combating that evil can require that you commit violent, even suicidal, acts.
The Thuggees of India during their several centuries of existence may have killed by slow strangulation 1 million people as sacrifices to the Hindu goddess Kali. The Thugs had no political objective and, when caught, looked forward to their execution as a quick route to paradise.
In the Muslim world, one kind of terrorism, assassination, has existed since shortly after the death of the prophet Muhammad. Of his early successors, three were killed with daggers. The very word "assassin" comes from a group founded by Hasan Ibn al-Sabbah, whose devotees, starting in the eleventh century, spread terror throughout the Muslim world until they were virtually exterminated two centuries later. They killed rival Sunni Muslims, probably in large numbers. Perhaps one-third of all Muslim caliphs have been killed.
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