Saladin had by now agreed truces with his Zengid rivals and the Kingdom of Jerusalem (the latter occurred in the summer of 1175), but faced a threat from the Isma'ili sect known as the Assassins, led by Rashid ad-Din Sinan. Based in the an-Nusayriyah Mountains, they commanded nine fortresses, all built on high elevations. As soon as he dispatched the bulk of his troops to Egypt, Saladin led his army into the an-Nusayriyah range in August 1176. He retreated the same month, after laying waste to the countryside, but failing to conquer any of the forts. Most Muslim historians claim that Saladin's uncle, the governor of Hama, mediated a peace agreement between him and Sinan.

Saladin had his guards supplied with link lights and had chalk and cinders strewed around his tent outside Masyaf—which he was besieging—to detect any footsteps by the Assassins. According to this version, one night Saladin's guards noticed a spark glowing down the hill of Masyaf and then vanishing among the Ayyubid tents. Presently, Saladin awoke to find a figure leaving the tent. He saw that the lamps were displaced and beside his bed laid hot scones of the shape peculiar to the Assassins with a note at the top pinned by a poisoned dagger. The note threatened that he would be killed if he did not withdraw from his assault. Saladin gave a loud cry, exclaiming that Sinan himself was the figure that had left the tent.

Viewing the expulsion of the Crusaders as a mutual benefit and priority, Saladin and Sinan maintained cooperative relations afterward, the latter dispatching contingents of his forces to bolster Saladin's army in a number of decisive subsequent battlefronts.