[영문]How and why do movements transition from everyday resistance to overt collective action? This article examines this question taking repressive environments and threat as an important case in point. Drawing on primary and secondary data sources, I offer comparative insights on resistance group dynamics and perceptions of threat in three Nazi death camps?Sobibor, Treblinka, and Auschwitz?between 1941 and 1945. Prisoners formed resistance groups at each camp, but collective revolt occurred in only certain cases: when the collective perception of threat at a given camp was viewed as both immediate and lethal. The interpretation of changing, threatening conditions, and an understanding of structural and interactional opportunities for group identity and tactical strategizing, are vital for understanding collective action in repressive environments. I conclude by discussing these lessons pertaining to threat and their implications for repressive contexts and broader social movement theorizing.