caliph
The supreme religious and political authority of Muslims, considered successor of Muhammad (Arabic: khalifa = deputy). He was the head of the Caliphate, the religious state of the Arabs.

domestikos ton scholon
Commander of the regiment of scholae. The first officer with this title appears in 767/8. In the 10th C the domesticos became very powerful among the army of the themata; in mid-10th C the office was divided in two, domestikoi ton scholon of the East and those of the West, commanders in chief of the eastern and the western provinces´ army respectively.

emir
(from Arabic amir) Emir meaning "commander" or "general", later also "prince". Also a high title of nobility or office in some Turkic historical states.

strategos ("general")
During the Roman period his duties were mainly political. Οffice of the Byzantine state´s provincial administration. At first the title was given to the military and political administrator of the themes, namely of the big geographic and administrative unities of the Byzantine empire. Gradually the title lost its power and, already in the 11th century, strategoi were turned to simple commanders of military units, responsible for the defence of a region.

tagmata (pl.)
Military units stationed in Constantinople and its outskirts during the Middle Byzantine period. The most important tagmata were that of the Scholae, the Excubitors (these originated from respective units of the Early Byzantine period and were organized into an imperial guard and a central strike force by Constantine V), the Vigilia (established by Irene the Athenian) and the Hikanatoi (established by Nicephorus I).