Not The Best Comparison

Question: Is there a better way to represent the self-defense principle as it relates to war?

I was recently reading from my contemporary moral issues book and saw a simplified representation of war. It was simplified in order to show how killing in war is justified (using the principle of self-defense). While I do not deny that it is justifiable to kill another person is self defense, I feel that the book inadequate represent a war like scenario; it failed to take into account the other side. Basically, it was simplified as such, S (Smith) and J (John) have just encountered each other, S is enlisted by W (Wife), who says that J has done her some wrong, to kill J. Believing W, S sets out to kill J. J, in response, is justified in killing S because S was of immediate threat to him. He is also justified in killing W, under the assumption that Killing W will cause S to relent or in someway become easier to subdue. It is important to recognize that S has done nothing to deserve killing other than attempt to kill J based off of W's assertion of J's misdoings.

I also think that P1(People 1) tend to think of their side as being the J of war, killing in self defense, but P1 refuse to recognize that P2 consider themselves as J as well. I will draft a more adequate, in my opinion, model for class and then post that here.