I personally believe that Jesus calls us to "love our enemies" and that this means not killing them for any reason whatsoever. My personal objection to war goes far beyond the whole nuke thing to even self defense.
I fully agree with Jesus on this one, but sometimes I wonder what I would do in a situation where this belief was really challenged. I hope I don't have to find out.
My view is that how we act in these "crisis scenarios" isn't super important. It's how we act in the everyday situations that matters.
So I ask myself, "What am I doing right now to reduce war?" or "What am I doing right now to help the homeless living in my city?" This is how I measure whether or not I'm following Jesus.