In this classic book on the phenomenon of the guerrillas, Jon Lee Anderson addresses with his usual meticulousness and clarity one of the crucial phenomena to understand the history of the second half of the twentieth century. To do so, he traveled to see firsthand the realities of the Mujahideen of Afghanistan, the FMLN of El Salvador, the Karen National Liberation Army of Burma, the Polisario Front of Western Sahara and Palestinian cells fighting against Israel in the Gaza Strip. Independently of the luck experienced by the different guerrilla movements, the breath that runs through his research is "to understand what it is that motivates ordinary people to go to war, to make the conscious decision to kill and die for an ideal that exists, at least at the beginning, just in their heads. It seemed to me that the first step was the crucial one, since it involved the crossing of an invisible line, towards a territory where death, and not life, was the main certainty ".