Since most people don't know what Fedayeen is, I figured I'd post this here, (just a copy and paste from something else, not my work)
Unable to mount a conventional military army, the Nizāriyya developed a form of asymmetric warfare transforming the act of political assassination into a system of survival and defense against their foes. They trained highly capable sleeper commandos (trained in languages, science, trade, and so on) known as Fedayeen, who would covertly infiltrate enemy positions and remain undercover. If Nizari civilians were facing pogroms or their forts faced imminent attack, the Fedayeen were activated to prevent an attack.
Map of the crusader states, showing the area controlled by the Assassins around Masyaf, slightly above the center, in white.
Fedayeen used their well-known skills for political goals without necessarily killing; for example, a victim, usually high-placed, might one morning find a Hashshashin dagger lying on his pillow upon awakening. This was a plain hint to the targeted individual that he was not safe anywhere, that maybe even his inner group of servants had been infiltrated by the assassins, and that whatever course of action had brought him into conflict with the Hashshashins would have to be stopped if he wanted to live.[5][6]
Within Persia they employed their tactics directly against the Seljuk Turks, who had been persecuting Nizari people. They were meticulous in killing the targeted individual, seeking to do so without any additional casualties and loss of innocent life, although they were careful to cultivate their terrifying reputation by slaying their victims in public. Typically, they approached using a disguise, or were already sleeper agents in an entourage. Preferring a small hidden blade or dagger, they rejected poison, bows and other weapons that may have allowed the attacker to escape and live.
Within the Levant it is believed that Saladin, incensed by several almost-successful Hashshashin attempts on his life, besieged their chief Syrian stronghold of Masyaf during his reconquest of Outremer in 1176. He later lifted the siege after parley, and thereafter attempted to maintain good relations with the sect. The sect's own claims tell of an unsourced account in which assassin Rashid ad-Din Sinan sneaked into Saladin's tent in the heart of his camp, and left a poisoned cake and a note on Saladin's chest as he slept saying "You are in our grip" and then sneaked back out of the camp unharmed. Another account tells of a letter sent to Saladin's maternal uncle, vowing death to the entire royal line; perhaps no idle threat. Whatever the truth of these accounts, Saladin's uncle clearly heeded their warning, and desisted.
The Hashshashin often took contracts from outsiders. Richard the Lionheart was among those suspected of commissioning them to assassinate Conrad de Montferrat.[7] In most cases the Hashshashin were aimed at retaining the balance of their enemies.[citation needed]
Notable victims include the notable Abbasid vizier Nizam al-Mulk (1092), the Fatimid vizier al-Afdal Shahanshah (1122) (responsible for imprisoning Nizar), Ibn al-Khashshab of Aleppo (1125), al-Bursuqi of Mosul (1126), Raymond II of Tripoli (1152), Conrad de Montferrat (1192), and Prince Edward (later Edward I of England) was wounded by a poisoned Hashshashin dagger in 1271.