In 2014, eight years prior to the Russian invasion of Ukraine in 2022, Russian-backed separatists seized parts of the Ukrainian regions Luhansk and Donetsk. Shortly thereafter, thousands of Ukrainians voluntarily enrolled to various paramilitary battalions. Unlike the Right Sector's Volunteer Ukrainian Corps (RS VUC), almost all battalions were incorporated into Ukrainian official defence structures. Applying uncertainty-identity theory and based on interviews, observations, and documents, this study investigates the attractiveness of RS VUC prior to the 2022 war, motivating the fighters to join this organisation and to remain in it. The study found that fighters of RS VUC distrusted society, the wider population, and state authorities. RS VUC, with its high fighting morale, discipline, family-like relationships between fighters, as well as its clear ideology and boundaries between ‘us’ and ‘them’, were attractive to the fighters since its unambiguous group prototypes and high entitativity, reduced the fighters’ self-uncertainty regarding their social identity in an uncertain environment. The findings also revealed that the fighters’ choice to join RS VUC can be understood as a rational decision, since RS VUC's group entitativity provided the fighters with moral and emotional benefits, as well as maximised their chances of survival.