The last years of the 18th century defined a period of dynamic military and political period for the Ottoman Empire. Rapid changes occured in the military as a result of political upheaval during the Selim III period. These changes focused on the defense of the capital of the empire - Istanbul, and on strengthening its position as a defensive center of the empire. The importance of urban space to these military aims suggests that Istanbul was predominantly a military city during the reign of Selim III. The military reforms instituted for the defense of the Ottoman Empire resulted in the construction of barracks, powder magazines, shipyards, arsenals, forts, bastions and redoubts. Some areas that included civilian structures that were used for military equipment trials. were also converted to military operation and defense sites. In this article, the military identity of Istanbul during the last years of 18th century is examined from this perspective in the light of archive documents.