Thanks for the comments everyone! Here are some of my initials thoughts that prompted my question.

I was thinking that I could come to an estimate of the prior probability in this way:

For every given war there is a side that is justified in violence and a side that is not justified in violence.

OR

Both side are unjustified in violence

It can't be the case that both sides are justified. Violent conflicts can't happen between two justified parties.

Given the above realization, I should expect to randomly find myself in the justified country no more than half the time a violent conflict arises. Actually, the prior probability that I live in justified country is most likely less than .5 since many wars have probably involved both parties sharing guilt in the conflict.

That's as far as I got and then I posed the question here.

Thoughts?

Emile, yeah, what ""justification" is is certainly a question, but what if we just assume a definition of just war and work from there? Could you not then look at the evidence of the other countries wrongs and so forth and come up with a probability?

You misunderstand the difference between barefoot and shod walking. There really isn't one. The difference is with barefoot running. In this case the forefoot lands first.