To the question on the system of border fortifications of the Principality of Theodoro in the 15<sup>th</sup> century
At the beginning of the 15th century in southwestern Taurica the Post-Byzantine state entity, the Principality of Theodoro, was finally formed. It bordered on the Crimean Ulus of the Golden Horde, and subsequently by the Crimean Khanate, and the Genoese Gazaria arisen as a result of the collapse of the Crimean Ulus. The rulers of Theodoro created a system of border fortifications to defense frontiers of the Principality. It included fortifications functioning for many centuries, as well as those constructed in the 15th century by the population of Theodorits’ Gothia following the traditions of Provincial-Byzantine school of fortification. Features of such construction architectural techniques are most fully represented in all fortifications of the Principality of Theodoro. The system of border fortifications had its local peculiarities (South-Western Crimea, South shore), but its common feature was absence of a clear borderline. The borderline was «blurred», and there was existed a kind of «contact zone», the area size of which depended on different factors. This system existed until 1475, when the Ottoman Empire conquered the Genoese possessions in the Crimea and the Principality of Theodoro.