The paper examines the cases of technology-mediated assertion of citizenship in Ukraine and Belarus in 2020-2022. Through the lens of the theory of socio-technical systems, the citizenship agency is described in terms of choice, voice, and engagement: choice of performing citizenship under pressure; use of technology to raise the voices of civil society, build up the cooperation networks and engage others in the proactive problem-solving. This chapter presents a case study of citizen practices in Ukraine and Belarus that illustrate how citizen acts of engagement, cooperation, and creation of technology-empowered services affect the social and political agenda in both countries. Such an analysis aims to shed light on the transformation of citizen agency in post-Soviet societies and the role of citizen engagement in changing the course of the Russian war for domination in the region.  The paper explores relational and performative perspectives of technology-mediated citizen participation in the realm crossing civil society, policymaking, and defence. The case of Ukraine explains how citizens’ technology-mediated participation contributes to resisting Russian aggression in terms of engagement in local communities involving national defence. Citizen activation, using digital technologies in cooperation with authorities matters critically for the collective reconstruction of the country after the war, on the one hand, and for developing an active civil society essential for strengthening of their democratic institutions, on the other. The case of Belarus reveals some signs on how the civil society creates and protects citizenship agency in adverse and repressive conditions, through strategies, tools and services parallel to- or replacing the authoritarian institutions. Our analysis of technology-enabled cooperation between Belarusian civil society in exile and those inside Belarus contributes to understanding of global citizenship mediated by technologies