You're discounting the idea that being a brave man still has any reproductive advantage. I doubt very much that a fearful man is as attractive to women as a brave man, even in modern times.
I know several people who have escaped a war-torn country and had a successful life elsewhere, instead of getting affected by military propaganda, and possibly losing everything just because of other people's territorial conflicts.
One especially big confound here is remembering the distinction between having sex and having children. From an evolutionary standpoint, the latter is the only thing which matters and unlike animals humans have contraception which completely changes the situation. From an evolutionary perspective the stereotypical bad boy who’s sleeping around constantly might not have even as many children as the cautious, financially stable guy who is monogamous because the former guy’s partners are looking for fun while the latter’s is intentionally trying to start a family.
Edward R. Murrow
What is it with people nowadays, can't there be at least some room for touching this type of sensitive topic?
My post seems to become a downvote magnet. I just wanted to try an unusual perspective that is seldom talked about.
As for general jingoistic propaganda, it's as old as time. I'd also consider it immoral and irrational. Interesting though, as it benefits societies and not (fighting) individuals, and so should have a complex evolutionary dynamics (maybe like with worker bees). _Dulce et decorum est pro patria mori_.