This paper analyzes the history of the technopolitics of the Peace Dam, which was built in response to the inundation threat of the North Korea’s Imnam Dam in the 1980s and extended in the early 2000s. Over two decades, changes in the definition of the Imnam Dam threat and the socio-political context surrounding it led to the modification of the Peace Dam’s structure and political meanings. This paper highlights how even seemingly immutable infrastructure technologies can have their functions and political meanings redefined and transformed based on the changes in the material conditions and the socio-political contexts in which they operate. The analysis focuses on the extension of the Peace Dam during the Kim Dae-jung administration, which was influenced by the heightened interest in efficient water resource management and the geopolitics of the North-South border region. It was characterized by the ‘hostile cooperation’ relationship between North and South Korea, in which the military vigilance and the goal of peaceful coexistence coexisted. This paper’s attempt to reinterpret the political meanings of the Peace Dam by examining its history of ‘modification’ provides a method for understanding the history of technopolitics in a more nuanced way.