War is a very special human activity. It is both absolutely terrible and relatively commonplace. We devote enormous resources to its preparation, prosecution and commemoration, while we pray that it will never happen again. In modern times, it has helped to define national stories in rarefied terms of sacrifice and courage, while the reality of battlefield slaughter is brought into our living rooms by the nightly television news. Because humans recognize its special nature, they have since at least the time of Augustine in the fourth century CE constructed the conditions for just warfare, especially so as to distinguish the killing in war from murder. One of the key components of these conditions is civilian immunity. The classic theoretical exposition of the general rules of warfare was developed by Hugo Grotius in the seventeenth century; the classic treaties regulating conduct towards non-combatants in warfare are embodied in the Geneva Convention of 1949. The procedures and limitations in these and subsequent treaties are not always observed – otherwise a volume such as this would be happily redundant. In a fight to the death, where crucial matters such as national survival or religious identity are often at stake, the notion of playing by ‘Marquess of Queensberry rules’ often gets short shrift.