Uhh, what does Kapikulu mean? 
It's the name of the army branch in Ottoman Empire, which was directly under the command of the sultan. It included sub branches like Janisseries and Sipahis that you might also know. The direct translation is "slaves of the door" but the meaning is generally accepted as "guards of the hall" or "guards of the palace". This branch was created in the early eras of the empire to strengthen the central authority, the palace, which was a bit weak against the wills of the border commanders (Beys, Begs ) of the empire. Kapikulu branch played an important role to help the Ottomans switch from a country that grows with border commanders' conquests, into an empire ruled by the central palace.
