Fundamental principles of humanitarian law

Like Grotius, jurists and philosophers took an interest in the regulation of conflicts well before the first Geneva Convention of 1864 was adopted and developed. 
In the 18^th century, Jean-Jacques Rousseau made a major contribution by formulating the following principle about the development of war between States: “War is in no way a relationship of man with man but a relationship between States, in which individuals are enemies only by accident; not as men, nor even as citizens, but as soldiers (...). Since the object of war is to destroy the enemy State, it is legitimate to kill the latter’s defenders as long as they are carrying arms; but as soon as they lay them down and surrender, they cease to be enemies or agents of the enemy, and again become mere men, and it is no longer legitimate to take their lives.”

In 1899, Fyodor Martens laid down the following principle for cases not covered by humanitarian law: “(...) civilians and combatants remain under the protection and authority of the principles of international law derived from established custom, from the principles of humanity and from the dictates of public conscience.”
The above, known as the Martens clause, was already considered a standard part of customary law when it was incorporated in Article 1, paragraph 2, of Additional Protocol I of 1977.


While Rousseau and Martens established principles of humanity, the authors of the St. Petersburg Declaration formulated, both explicitly and implicitly, the principles of distinction, military necessity and prevention of unnecessary suffering, as follows: “Considering: (...) That the only legitimate object which States should endeavour to accomplish during war is to weaken the military forces of the enemy; That for this purpose it is sufficient to disable the greatest possible number of men; That this object would be exceeded by the employment of arms which uselessly aggravate the sufferings of disabled men, or render their death inevitable.”

The Additional Protocols of 1977 reaffirmed and elaborated on these principles, in particular that of distinction: “(...) the Parties to the conflict shall at all times distinguish between the civilian population and combatants and between civilian objects and military objectives and accordingly shall direct their operations only against military objectives.” (Art. 48, Protocol I; see also Art. 13, Protocol II).

Finally, the underlying principle of proportionality seeks to strike a balance between two diverging interests, one dictated by considerations of military need and the other by requirements of humanity when the rights or prohibitions are not absolute.