Thought provoking yes. I agree with the principles but the analogy of the o/p not sure. Are you saying that's what should happen in war? Plus 'invade' another country gives the question why?
I think the short answer is one like, "if one had to because there was no other option." Like all hypotheticals it depends on certain presumptions that we could probably "what-if" forever. My first reaction was similar to yours, but after a little while I made the connection that spies are information gatherers, much like the nerves in the body.