You basically have different situations that would generally be considered more or less acceptable:
- Intentional harm of the innocent (murder)
- Coincidental harm of the innocent (knew it was likely, manslaughter)
- Mutual oppositional violence (war)
- Defensive violence (repel invaders)
- Accidental harm of the innocent (no idea it would happen)
- Mutual permitted violence (boxing)
The interesting thing that occurs to me after writing a list in diminishing order of severity leads me to think about what the West is doing in the Middle East. We're being sold the "war in Iraq" as a war (severity 3), but really that's not quite right. The people in the country are repelling invaders (severity 4), but the US is fighting an unjustified war of aggression, which is pretty much murder (severity 1).
Now, to say the US should pull out right now, or even on a timetable, is a much more difficult issue. They should not be there, and I've maintained that since long before they even were there. They've made a right nasty mess of the Iraq and potentially ruined the US economy with massive debt, but there isn't any good way out now. That is why any nation worth any respect whatsoever doesn't involve itself in wars of aggression.