FEAH teh stoner POWA!

Around the time of the first crusade (1090) Cairo, Egypt was still being ruled by the Fatimide dynasty. The Leader of a small Shia sect of Muslims lead by a guy named Hasan-i Sabbah vied for the throne.
They were persecuted by the predominant Sunni population and slaughtered right and left by the Mongols.
Hasan was eager to get back at his enemies but lacked the numbers of an amassed army to do so.
Instead he got young men to hit the hash pipe and have happy dreams about what heaven was like.
Since any hash smoker knows the drug induced dreams are the most realistic pleasant closeness you'll ever get to your fantasies coming true, Hasan convinced his followers that what they dreamed of was their harems in the afterlife with their houris awaiting those who follow Allah's will. (Based off Marco Polo's accounts from his visit to Alamut in 1273)

Eager to secure their place at the end of the one way ticket, the "Hashish eaters" trained to become the "True left hand of Allah".
They used daggers and stealth to kill people others considered untouchable. So great was their stealth that even the crusaders in their fortified towers feared them (no one before thought to masquerade as a servant, open an new doorway in the dark side of your tent, and give you a few new orifices).
They never allowed themselves to be seen and rejected any weapon that might allow a witness to discuss them before dying (a.k.a. poison or crossbows). They also learned to fight only using their hands and feet in an old-school style of Kung-Fu. They tended to opt for public killings to up the fear factor and there is very few records of them killing innocent bystanders (They had the Sicilian idea of: you only need 1 bullet to kill 1 man)

The "Hashishin's" or "Hashashin's" fought with no honor, paying heed to Marcinko's 6th rule of combat: Thou are not judged by the means as thou art by the results.
The crusaders had a killer time remembering and pronouncing the cult's name (especially the rolled "h") and pretty quickly Christendom came to feah "assassins".

Next time you hear someone being called a true assassin check to see if his turban matches his shoes.