This is a simplification. Defending yourself against unprovoked attack is not juvenile, although there are moral systems that advocate rolling over and giving up if you are attacked. And there is a whole spectrum of combat actions where "defense against unprovoked attack" is one extreme.
In industrialized countries, wars of aggression are usually never profitable, but the same can unfortunately not be said for less-developed societies. Even Europe didn't find this obvious until after World War 2. So I guess it ends up being a question of how you define "sophomoric".
Actually, wars of aggression are almost never profitable. Accumulating riches via conquest is almost always a myth, because armies a) destroy much that is of value and b) are unbelievably expensive.
"Wealth through superior firepower" has hardly ever been achieved. Even Rome mostly got rich through trade after its armies conquered Europe and North Africa, and a lawful peace was imposed. Had everyone been economically rational pretty much the same end could have been achieved through trade (spoiler: not everyone is economically rational.)
Simple looting of the kind the Spanish engaged in in the New World was never a very good path to wealth, partly because its first effect was to create massive inflation (if you use gold as money and inject vase amounts of gold into your economy without increased productive capacity, you get inflation, not wealth.)
So the conditions of gaining wealth by war are very, very narrowly defined. It's not impossible, but it's amazingly difficult.
There are defensible moral reasons for engaging in mass organized violence--I support the current American efforts to kill people in Northern Iraq, for example--but economic rationality (profitability) is never one of them, because the first step to creating wealth is never to engage in the wholesale destruction of everything the creation of wealth depends on.
Interesting that wars of aggression have almost never been profitable; this fills a hole in my understanding. I've always understood that this fact only became obvious after WWII, and almost 10 years of terribly destructive fighting in Europe and elsewhere.
Interesting, you know more than me but afaik it is correct. Both in facts and arguably in moral.
Since you brought up Rome in discussing payback for warfare, you could also ask "Cui bono" here -- "who benefits?"
A war is potentially just like a gold rush, the people getting rich are the ones selling the tools to dig or make war.
Just look at my native Sweden, we managed to stay out of a few wars and shamelessly sold high quality steel to the countries fighting. It made Sweden go from the bottom to the top in Europe.
What this implies about lobbying and how wars starts I'll leave to the imagination.
(I might also add that IS has declared war on the democratic world. So trying to stop their expansion is arguably self defence.)
In industrialized countries, wars of aggression are usually never profitable, but the same can unfortunately not be said for less-developed societies. Even Europe didn't find this obvious until after World War 2. So I guess it ends up being a question of how you define "sophomoric".