Between colonial wars and current « (counter-) insurgencies », we will examine the global phenomenon of partisan warfare in the 20th century, focusing on the European empires (including the Nazi Germany). Neither a simple continuation of « archaic » forms of war in « barbaric » or « pre-modern » societies, nor the great novelty that many contemporaries saw in the « people’s wars », it appears as one of the major sites of the restructuration of imperial spaces and of a global renegotiation of political orders in a context of imperial collapse, rapid social change and diffusion of European political discourses and military technique.