GENERATIONS OF PHILOSOPHERS HAVE believed, and national rulers have acted on, the principle that might renders questions of right irrelevant when it comes to warfare. In doing so they have conformed to the position ascribed by Thucydides to the Athenian generals in their dialogue with the Council of the Melians: ‘The strong do what they have the power to do and the weak accept what they have to accept’. What the Melians had to accept in that particular situation was immediate surrender or siege and the slaughter or enslavement of almost the entire population. Elsewhere in The Peloponnesian War, Thucydides describes a debate over the treatment of the defeated population of Mytilene that makes no reference to the morality of the alternatives but which is argued entirely on the basis of prudential considerations.

The Athenian approach was replicated through the ages with perceptions of political and military necessity dictating the conduct of war. For many rulers and commanders there was no practical difference between enemy combatants and enemy civilians: both were responsible for their state's behaviour and contributed to its capacity to wage war; and both could revolt against occupation if left free when defeated. Nobody could be described as innocent. Where civilians were treated humanely or damage to their environment was limited, it was for prudential rather than ethical reasons.