With the partitioning in 1373 of the domain of Nikola Altomanovic, a Serbian feudal lord, the old political core of the Serbian heartland was shattered and the feudal Bosnian state considerably extended to the east. The region was crossed by the Tara river, mostly along the southeast-northwest "Dinaric course". Although the line along which Altomanovic?s domain was partitioned has been discussed on several occasions and over a comparatively long period, analyses show that the identification of its section south of the Tara is still burdened by a number of unanswered questions, which are the topic of this paper. An accurate identification of this historical boundary is of interest not only to historiography, but also to archaeology ethnology, philology (the history of language and dialectology in particular) and other related disciplines. The charters of Alphonse V and Friedrich III concerning the domain of herceg Stefan Vukcic Kosaca, and other historical sources relating to the estates of the Kosaca cannot reliably con?rm that the zupa of Moraca belonged to the Kosaca domain. The castrum Moratsky and the civitate Morachij from the two charters stand for the fortress near the village of Gornje Morakovo in the zupa of Niksic known as Mrakovac in the nineteenth century, and as Jerinin Grad/Jerina?s Castle in recent times. The zupa of Moraca, as well as the neighbouring Zupa of Brskovo in the Tara river valley, belonged to the domain of the Brankovic from the moment the territory of zupan Nikola Altomanovic was partitioned until 1455, when the Turks ?nally conquered the region thereby ending the 60-year period of dual, Serbian-Turkish, rule. Out of the domain of the Brankovic the Turks created two temporary territorial units: Krajiste of Issa-bey Ishakovic and the Vlk district (the latter subsequently became the san?ak of Vucitrn). The zupa of Moraca became part of Issa-bey Ishakovic?s domain, and was registered as such, although the fact is more di?cult to see from the surviving Turkish cadastral record. The zupa of Moraca did not belong to the vilayet of Hersek, originally established by the Turks within their temporary vilayet system after most of the Kosaca domain had been seized. It was only with the establishing of the San?ak of Herzegovina that three nahiyes which formerly constituted the Zupa of Moraca (Donja/Lower Moraca, Gornja/Upper Moraca and Rovci) were detached from Issa-bey?s territory and included into the San?ak of Hercegovina. It was then that they were registered as part of that San?ak and began to be regarded as being part of Herzegovina.