Janissary

The Janissaries (Ottoman Turkish: Yeniçeri meaning new soldier) were specially trained soldiers of the Ottoman Empire and the private guard to the Sultan. During Ezio's time in Constantinople, the Janissaries actively sought to prevent Ezio Auditore da Firenze from locating the Seals of Altaïr that were scattered throughout the city. Eventually, Ezio killed off one of their high commanding officers, forcing them to resort to patroling the whole of the Golden Horn, as well as blocking the port in an effort to prevent him from escaping the city. However, this ulitmately failed.

History
Janissaries created by Sultan Murad I were Christian boys from conquered countries levied into the Devsirme system (Collection of Children ) mostly the stronger children would be chosen and probably become Janissaries the intelligent ones would become scientist, architects etc. the Janissaries became the Ottoman empires first standing army and they all learned Islam and became muslim, they were infantry units that formed the Sultans household troops and bodyguard and eventaully they were abolished by Sultan Mahmud II in 1826 with the Auspicious Incident.