In circumstances of power inequality, and when there is doubt about the justice of going to war, opposing combatants are traditionally held to be moral equals. Each is as blameless as the other for the overall conflict (jus ad bellum), and all are equally required to fight justly (jus in bello). This moral equality is a point of commonality among combatants across countries and cultures, and even between armed enemies in war it is sometimes a source of mutual respect. The moral equality of combatants is, moreover, the basis for a warrior ethos; a sense of professional identity and purpose built around virtues and rules. The precise content and contours of this ethos vary across time and space, but it always has sociological significance too as a means of differentiating warriors and non-warriors (civilians) within a given society. Some authors prefer to draw a sharp distinction between the terms ‘warrior’ and ‘military professional’ because the former, they argue, evokes the caricature of someone who is old-fashioned, ethically non-constrained and even barbaric. Roger Wertheimer, for example, refers to ‘pre-professional warriors [who] have often been enthusiastically ruthless, glorying in plunder, pillaging, raping, enslaving, massacring, torturing, untroubled by any doubt that the victor may despoil the vanquished at his pleasure’.1 For present purposes, any such distinction is rejected in favour of the notion that ethical ‘constraints and worries have traditionally been seen as part and parcel of the ideal military character’.2 This then enables the warrior ethos to be seen as integral to military professionalism.