Fortification Peculiarities of Frontier Fortresses in the Urals and Western Siberia in the 18<sup>th </sup>Century
The article deals with the features of fortifications located in the Uy and Irtysh border lines which were a separate part of the Orenburg and Siberian lines of the 18th century. The aim of the article is to identify characteristics of fortified fortresses on these lines. The authors have used traditional methods of historical research, namely historical and retrospective, historical and comparative ones. To the authors' mind, the Irtysh line built in the early 18th century laid the foundation for the tradition of protection of borders which was later used in the organization of defensive structures in the Urals and other parts of the borders of the south of Western Siberia. An analysis of the structures on the Irtysh and Uy lines has shown some differences in the methods of strengthening the walls. The internal construction of fortresses was almost the same. Fortifications erected on these lines were a significant link of a chain of Russian border defensive lines consisting of fortification units built at different times, being different in hierarchy and forms as well. The results can be used in further studying the history of fortification of the Trans-Urals, Siberia, and Russia in general.