In 1176, Ṣalāḥ ad-Dīn's army laid siege to the fortress of Masyaf, home to the Levantine Brotherhood of Assassins. The Order's leader Al Mualim, entrusted Umar Ibn-La'Ahad with the task of infiltrating Ṣalāḥ ad-Dīn's tent within the Ayyubid camp to deliver a letter to the Sultan. However, Umar was discovered and was forced to kill an Ayyubid noble. The next morning, Ṣalāḥ ad-Dīn sent his uncle Šihāb ad-Dīn to make peace with the Assassins, in exchange for taking Umar's life, whose identity they had uncovered by torturing the Assassin Ahmad Sofian. Umar volunteered to have his life taken, and the Ayyubid government and the Assassins maintained several years of relative peace.
In 1189, European Crusaders invaded the Holy Land under the control of the Ayyubid dynasty in an attempt to reconquer the land. In 1191, after Robert de Sablé, Grand Master of the Templar Order, recruited several key figures in both the Crusader and Saracen armies, Altaïr Ibn-La'Ahad was sent by Al Mualim to kill them, disrupting the peace between the Assassins and the Ayyubid dynasty. The Crusaders and Saracens were eventually rallied against the Assassins by de Sable, though Altaïr managed to convince the Crusader leader Richard the Lionheart of Robert's conspiracy to take the Holy Land for the Templars.
In 1250, the Mamluks rebelled against the Ayyubid dynasty. Using the Scepter of Aset given to them by an Egyptian Assassin, they killed the reigning Sultan and took over the government in Egypt, starting the Bahri dynasty.