This chapter discusses a mechanism linking revolutionary terrorism and interwar development paths. The mechanism relates to the constraints imposed by the community of support on the terrorist groups. According to the argument, in those places in which the radical Left was stronger (as revealed by a powerful anarchist and/or communist movement), the likelihood of a segment of the Left supporting armed struggle was higher. This was typically the case in countries with a non-liberal past. To show this, evidence about negative cases is examined in depth. Negative cases refer to armed groups that had the capacity to kill but refrained from doing so. Almost all of the negative cases (such as the Weather Underground Organization) are concentrated in countries that had a liberal past throughout the twentieth century. In countries with a non-liberal past, repression of the protests of the late 1960s and early 1970s was interpreted by the radical Left as evidence of the persistence of an authoritarian state operating under a democratic facade; this deficit of state legitimacy was crucial for radical activists to support revolutionary terrorism.