Kleisoura (Byzantine district)

In the Byzantine Empire, a kleisoura (, "enclosure, defile") was a term traditionally applied to a fortified mountain pass and the military district protecting it. By the late 7th century, it came to be applied to more extensive frontier districts, distinct from the larger "themata", chiefly along the Empire's eastern border with the Caliphate along the line of the Taurus-Anti-Taurus mountains (in the West, only Strymon was in its early days termed a "kleisoura"). A "kleisoura" or "kleisourarchia" was an autonomous command, under a kleisourarches (Greek: κλεισουράρχης). Eventually, most "kleisourai" were raised to full "themata", and the term fell out of use after the 10th century (in late Byzantine times, "droungos" had a similar meaning). Its Islamic counterpart in Cilicia and Mesopotamia was the "al-thughūr".