Full Idea
It would be naïve to doubt that the widespread acceptance of the moral equality of combatants has facilitated the ability of governments to fight unjust wars.
Clarification
The moral equality is between the just and the unjust, in combat
Gist of Idea
If all combatants are seen as morally equal, that facilitates starting unjust wars
Source
Jeff McMahan (Killing in War [2009], 1.1)
Book Reference
McMahan,Jeff: 'Killing in War' [OUP 2009], p.6
A Reaction
The point is that their armies are both compliant and seeing their actions as guiltless, which makes them perfect tools for evil. McMahan's ideal is an army which asks sharp questions about the justification of the war, before they fight it.