This thesis examines the meaning and construction of the debated concept of hybrid war/warfare in the existing scholarly literature. The identified research problem stems from the lack of reflection on the conceptual reasoning and thought that underpins the nature of war, which relates to the fact that a historical linguistic perspective is neglected in most studies on war. Through this study, conceptual history theory has demonstrated its utility in War Studies by illustrating the benefit of applying a historically focused lens on debated and contested concepts. Thus, demonstrating how both a synchronic and diachronic perspective is necessary to examine how the meaning and construction of a concept change over time.  The analysis aims to answer the question of how the meaning of the hybrid war concept has developed in the existing body of literature between 2008-2021. Based on the analysis, it was observed that the greatest shift in terms of the meaning and use of the concept occurred after the Russian annexation of Crimea in 2014. The previously optimistic anticipation of hybrid war in future was replaced with a more critical understanding of the concept itself, and the prospect of its future. All in all, the result of this thesis, beside the observed shift in the meaning and construction of the hybrid war concept, is that conceptual history theory can contribute to the understanding of contested and debated concepts related to the nature of war.