This article analyses the ascent of ‘Russian hybrid warfare’ (RHW) as a notion that transformed the understanding of national security in the Czech Republic in the short period of 2014–2016. It argues that the emergence of RHW as a specifically understood prime security threat was the result of contingent and often unruly social interactions across different settings, rather than a linear and centralised response to Russia’s actions. To capture this process, the concept of ‘assemblage’ is introduced and then defined as a temporary constellation of a variety of different actors, both public and private. Building on research interviews and documents produced in the RHW field, the authors then proceed in three steps. First, they chronologically trace the gradual emergence of the Czech RHW assemblage from a variety of different actors—bureaucrats, NGOs, academics, journalists—after Russia’s attack on Ukraine in 2014. Second, they unpack the inner workings of the assemblage by identifying the key actors and asking who did the assembling and how. Third, they look at how different actors were able to reinforce and/or transform their identities by being part of the assemblage, with an emphasis on the effects this had for the distinction between the public and the private.