In one real sense all war is a crime and all war is an atrocity. But in another sense there are distinctions between some thing that happen in war which can be seen tragic necessities, or terrible accidents - and some which are war crimes. If we don't accept that distinction it means that there's no difference between a soldier doing his duty and some SS extermination squad. Or the equivalent in other wars.

When Calley and his comrades rounded up the people of My Lai and shot them down, that was murder, every bit as much as when Timothy McVeigh exploded his bomb in Oklahoma. And if that was what Bob Kerrey did on that night in 1969, that was murder too. And if it was murder, anyone involved in a cover-up was an accesory to murder.

That being said, there are things that happen to people in war that can damage and change them in ways that diminish their personal guilt. Maybe if Calley and McVeigh hadn't gone off to war they wouldn't have turned into murderers. And maybe Bob Kerrey's account of what happened on that night is the truth, and he didn't shoot civilian prisoners in cold blood.

What matters isn't getting vengeance and judging individual people - it's finding the truth, and getting rid of the lies and the whitewash. That applies whether it's Bloody Sunday in Derry or Vietnam or Chile or Bosnia. Truth and Reconciliation, not vengeance - but the Truth comes first.