The canonical reading of Jaurès’s L’Armée nouvelle presents this work as an outdated reflection on the establishment of a socialist society supervised by intermediary bodies whose military training would be a major asset. Our reading goes beyond this historically situated approach to Jaurès’s book. We show that The New Army is not just a response to the General Staff, even less a “theorisation” of the transition to socialism, but that its aim is to rehabilitate the founding principles of democracy (ancient as well as modern), which rests on the constitution of an army of citizens: The “proletarian-soldier” of Jaurès is none other than the “farmer-soldier” of the ancient city and of Year 2 of the French Revolutionary calendar, transposed to the Industrial Age. Relying on a game-theoretical model, we highlight that this defence of democratic principles is backed by a discourse of the economics of war prevention in terms of self-protection.