I thought about this a lot when I was gathering "Another Day in Paradise; International Humanitarian Workers Tell Their Stories," and I continue to think about it. (This is a wonderful series, thank you.)
I agree with Nancy Soderbergh: War, in general, won't end in my lifetime. That said, much can be done to alleviate the "need" for war, or perceived "need."
Every conflict, every massacre has immediate and historical origins. Once ignited, once soldiers become killing machines, as they have been trained, other challenges surface. Think about the American soldiers recently who went berserk and killed innocents. War, by definition, is dehumanizing. I have an (unproven) theory that PTSD is partially the result of soldiers/fighters in psychic conflict with themselves as they kill and maim.