Today the word "assassin" refers to anyone who kills for a political purpose; originally, however, the name referred to a group of fanatical killers whose primary targets were the Seljuk Turks.
A terrorist organization associated with the Ismaili sect of Islam, the Assassins were established in 1090 by Hasan-e Sab-bah, an Iranian religious leader. Hasan was known as the “Old Man of the Mountain," a title that passed to each successive Assassin leader. Operating from a castle in a valley stronghold, the Assassins conducted acts of terrorism and political killing throughout the Muslim world, but particularly in Iran and Iraq. Because the Seljuks happened to be in power at that time, they were the principal target, and all attempts to uproot the Assassins proved fruitless.
During the Crusades, Assassins in Syria terrorized both Turks and Christians, but combined attacks by the Mongols and Mam-luks in the mid-1200s brought about the end of the terrorist group.
Crusaders brought the word "assassin" home with them, and eventually it entered the languages of Europe. It is thought that the name derives from the Assassins' use of the drug hashish. According to Venetian traveler Marco Polo, Assassin leaders would ensure their men's loyalty by drugging them and taking them to a garden where they could enjoy all manner of earthly delights—pleasures that, they were told, would await them in the afterlife if they died on the field of battle. Contemporary Ismaili sources, however, contain no mention of this "Garden of Paradise."
Local religious leaders, who in turn gave their allegiance to political leaders. This made it possible for conquerors to easily replace one another, because the religious leaders served as a buffer between the people and their rulers, who were often foreigners. Another important feature of Seljuk rule was the use of slave soldiers, a group of whom would soon rise to prominence in Egypt.