Cities have always drawn their growth and development from the thoughts and ideas of their initial designers and urban planners who have undoubtedly tailored the city's construction pattern to suit the environmental geography. Kermanshah is no exception to this environmental geography and has its own model of environmental defense. As the largest city in western Iran, Kermanshah is considered the uncontested city of the region due to its unique location and extensive sphere of influence. Kermanshah has been an important center of trade and an urban hub for many centuries, and today it ranks ninth in terms of urban population in the country. Kermanshah's role as a strong defensive fortress in the west of the country has made it the focus of governments in different eras. This underscores the importance of the physical-spatial development of Kermanshah as a result of defense factors in various historical periods. In this article, the Shannon entropy model is used to examine the development process. The results show circular development of the city until 1951, and linear growth from Sarab Taq Bostan in the north to Sarab Qanbar in the south until 1971. From this date onwards, the city has seen physical growth in the western and eastern areas, with the construction of industrial zones and residential areas in these regions, aimed at development plans and urban development. Moreover, practical challenges in some areas have affected urban development, with the political-military factors playing an exceptional role in the physical-spatial development of Kermanshah's metropolis.