[newby]

> I think it's wishful thinking to imagine soldiers will make the 'right' decision when the call comes.

I understood the point you are responding to differently than you - it is not about doing the (morally) "right" thing, it is about doing the self-preserving thing. I imagine there is always a lot of people willing to do horrible things when they can reasonably expect they will face no personal consequences (your Tiananmen Square massacre example, which would mean personal consequences for not doing it). The expectations are very different for officers hitting the launch button - they have to know that if they do it, it is very likely that they themselves and everybody they love will die or face horrible future in the post-apocalyptic world. I am not saying this means nobody will hit the button, I am just saying it makes doing it a lot harder and (hopefully) less likely.