The article explores the evolution of defensive fortifications in small towns of Volyn, using the examples of Dubno and Kremenets. It analyzes the transition from wooden fortifications to masonry bastion systems, influenced by changes in military strategy, construction technologies, and the political situation in the region. Significant attention is given to urban planning features, the role of fortifications in shaping city structures, and their adaptation to the natural landscape. The study examines the key stages of the development of Dubno and Kremenets castles and fortifications, including their initial wooden construction, reinforcement with stone walls during the heyday of medieval defensive architecture, and subsequent transformation into bastion-type systems. The structural features of these fortifications and their role in military conflicts from the 15th to the 18th centuries are characterized. Special attention is paid to the current state of preservation of the Dubno and Kremenets castles, their significance for the historical and cultural heritage of Volyn, and prospects for their conservation. Based on historical sources, archaeological research, and an analysis of architectural changes, conclusions are drawn about the main trends in the development of defensive fortifications in the region. The article incorporates the results of previous scientific studies, particularly the works of Pryshchepa (2010), Rychkov (2012), Pshenychnyi (2017), which examine the history of fortifications in Volyn, their architectural evolution, and military significance. These studies provide valuable insights into the structural changes of castles, their strategic functions, and the influence of European fortification trends on local defensive systems.