This paper aims to examine the constructional background and process of the Japanese military installations of Jisim-do, especially based on the military secret documents. Furthermore, it aims to analyze the characteristics of the remains. First, the study looked into the procedure of forcible occupation by Japan, involving the background of the designation and forcible accommodation of military reservations, and forced eviction by the purchase of land. Second, the study identified the background of construction, purpose, and construction period of each battery built throughout the ‘Fort maintenance period’ according to changes in international situations. Third, it is the 'Chukseongbu' that supervised the construction of fortresses. Fourth, the study considered a series of arrangement processes in which Jisim-do became a fortresses through『Yukgunsungdae-ilgi』, a military operations report for the Japanese army. Through this, it discovered a clear construction process, construction details, and the supply for Jisim-do. The study was also able to reveal the meticulousness in constructing firm facilities more promptly from the ‘design tactics’.