During the Ottoman period a number of Pontian Greeks converted to Islam and adopted the Turkish language. This could be willingly, for example so to avoid paying the higher rate of taxation imposed on Orthodox Christians or in order to make themselves more eligible for higher level government and regular military employment opportunities within the empire (at least in the later period following the abolition of the infamous Greek and Balkan Christian child levy or 'devshirme', on which the elite Janissary corps had in the early Ottoman period depended for its recruits). But conversion could also occur in response to pressures from central government and local Muslim militia (e.g.) following any one of the Russo-Turkish wars in which ethnic Greeks from the Ottoman Empire's northern border regions were known to have collaborated, fought alongside, and sometimes even led invading Russian forces, such as was the case in the Greek governed, semi-autonomous Romanian Principalities, Trebizond, and the area that was briefly to become part of the Russian Caucasus in the far northeast.