Ottoman Civil War

The Ottoman Civil War was a conflict between Bayezid II and his son Selim for the Sultanate of the Ottoman Empire. Ahmet, the oldest son of Bayezid, was chosen as the heir to the sultanate, which didn't go down well with Selim. Selim, who was third in line to the throne behind his brothers Selim and Korkut, decided to secretly gain the support of the Janissaries, who held him in high regard. Selim then engaged in conflict with Bayezid with the hope of taking the throne for himself. Meanwhile, in Constantinople, Ahmet was thinking of new ways to further his influence.

Ahmet's Plans
Ahmet, as the Grand Master of the Templar Order's Byzantine Rite, searched new ways of expanding his influence on the Ottoman Empire. One of these ways was to locate the "Grand Temple" of the First Civilization, which Ahmet believed they could find if they obtained access to Altaïr Ibn-La'Ahad's library in Masyaf. Ahmet entrusted his second-in-command Manuel Palaiologos with the Masyaf expedition and the search of the keys needed to open the library. In the meantime, Ahmet would focus his attention on matters of Constantinople.

Ahmet also plotted against his nephew Suleiman. The plan was for the Templars to infiltrate and abduct Suleiman. Were this successful, Ahmet would have later rescued him and be heralded as a hero. However, it didn't go as planned as Ottoman Assassins disguised as Italian minstrels, on orders of their leader Yusuf Tazim, killed all the infiltrated Templars.

End of the War
In March 1512, Ahmet traveled to Cappadocia, where Manuel Palaiologos and Shahkulu were forming an army. Ahmet arrived shortly after Italian assassin Ezio Auditore da Firenze killed Manuel and obtained the last of the keys of Masyaf. Revealing himself as the Grand Master of the Byzantine Rite, demanded all the keys for Altaïr's Library in exchange of Ezio's lover, Sofia Sartor, life. Ahmet then ordered the capture of Sofia, which resulted in the death of the Ottoman Assassins leader Yusuf Tazim. This infuriated the Ottoman Assassins and led them to an all-out assault on Constantinople's arsenal, where Ahmet was hiding.

Ahmet, confronted by Ezio, reminded him that he still had Sofia and arranged a meeting with him at the Galata Tower to exchange Sofia's life for the Masyaf keys. After some hostility between Ezio and Ahmet, Ezio finally handed over the keys just to be tricked by Ahmet by not giving him Sofia, giving him another woman instead. Ahmet had ordered Sofia to be killed in a square not too far from them and as Ezio run to save her, Ahmet hurried off to Masyaf. Ezio saved Sofia and they both proceeded to follow Ahmet's path. After managing to catch up with Ahmet's horse-drawn wagon and starting a chase, Ahmet obliterated Sofia's wagon, which led him into thinking that he got rid of both Ezio and Sofia. Unexpectedly, Ezio hanged to Ahmet's wagon and knocked from his seat, causing both men to fell off a cliff. After reaching solid ground, they engaged in a melee fight.

Selim, who was returning with his army to Constantinople, found his brother facing off Ezio. Revealing to Ahmet that his father had abdicated and had chosen him as his successor, he started strangling him knowing of his betrayal to the Ottoman Empire and his alliance with the Byzantine Templars. During the struggle, Selim pushed his brother off a nearby cliff, killing him in the process. Selim then turned to Ezio and told him that his son Suleiman spoke quite highly of him and that was because of this that he would spare Ezio's life with the condition that he never set foot on Constantinople ever again.

Aftermath
Selim became the first Sultan who was chosen by the Janissaries instead of the previous Sultan. This wouldn't last long however as he died eight years later of an illness. His son Suleiman, who was 26 at the time succeeded him and went on to become a great ruler, dubbing him Suleiman the Magnificent, as his reign engineered the Golden Age of Constantinople.

Ezio obtained the keys of Altaïr's library back and traveled to Masyaf where, after opening the door of the library, found both Altaïr's corpse and a memory seal which led him to locate Altaïr's Apple of Eden. Ezio refused to take the Apple but instead used it to speak to speak to his descendent Desmond Miles, removing his bracers and declaring the end of his life as an Assassin. Ezio relinquished as the Italian Assassin's Mentor and chose Lodovico Ariosto as his successor. Ezio retired to live with his family and died peacefully eleven years later.

The Byzantine Templars, after the death of Ahmet, were ultimately dissolved. His Assassin's counterpart, however, continued running now under the leadership of Dogan, one of Yusuf's lieutenants.

Reference

 * Assassin's Creed: Revelations