Keywords: Rousseau, state of war, law of war, state.
Two long fragments on war written by Rousseau have been recently merged in a single text. It is the first part of an unfinished work that he intended to produce about the «principles of the law of war». Rousseau moves from a definition of the state of war in order to show - by contesting Hobbes' assumptions - that the war can exist among the individual neither in a state of nature, or in a civil state. Rather, the state of war is natural among the States. If the aim of war is that of destroying the enemy State, the objective of war is the destruction of the «public person» whose unity is derived by the social contract and by the general will. These are the premises whence the true «principles of the law of war» have to be deduced.