In recent years, several studies have focused on the unique existence of "pro-government (regime) militias" in the context of recent conflicts. Inspired by these previous studies, this paper aims to clarify how the Kurdish nationalist militia organization, the People's Defense Units (YPG), has transformed its role throughout the Syrian Civil War (2012-), where a similar phenomenon can be observed. The position of the YPG and its political arm, the Democratic Union Party (PYD), in the civil war is too complex to be short-circuited by expressions such as "a third force". Therefore, this paper chooses to rely on existing research, specifically on the multiple types of militias proposed by Shinichi Takeuchi, an expert on regional conflicts in Africa. This paper then analyzes the functions of the YPG by using indicators based on the types of militias proposed by the researcher, such as "a vigilante band" and "a well-regulated militia," as well as indicators based on the general sense of labels such as "pro-government" or "anti-government". This approach ultimately revealed that the role (character and property) embodied by the YPG/PYD throughout the Syrian Civil War, especially when the civil war is divided into several time segments, merely follows the types or characteristics already proposed in existing studies, far from being given a new typology of militias which seemed necessary to be newly created.