On the 100th anniversary of the Declaration of St. Petersburg, the International Review of the Red Cross devoted to this important first document of the law of war an article examining the relation between the notion of the “legitimate object” of war as defined in the Declaration and the means of warfare used, whose lawfulness was declared to be limited by their conformance to that legitimate object and by their necessity. Since 1868 the law of international armed conflicts has been supplemented by Protocol I additional to the Geneva Conventions of 1949, which enlarged on the central point of the Preamble to the Declaration of 1868 — i.e. the concept of “maux superflus” (“superfluous injury or unnecessary suffering”); although it was not formulated as such until 1899 in Article 23 e) of the Regulations respecting the Laws and Customs of War on Land, it may, as we shall demonstrate, be traced back to the Declaration's Preamble. Protocol I broadened the concept's scope of application to include methods of warfare, but it also and above all introduced a new rule of considerable import by narrowing the definition of military objectives that may lawfully be attacked.