In the past, rulers looked at ways to expand their real estate. Larger tax base, more revenue, so you might poach on another rulers’ territory.
As time has moved on though, how smart is modern warfare? Other than the fact that death is final. I am speaking of economics.
Even if you “win” the war, what do you really win? The United States doesn’t want to conquer Afghanistan and Iraq.
It’s why many modern conflicts don’t involve nation-states. Some people I know think the concept of nation-state is becoming outdated. Some think an international elite run the world. I’m too low in the pecking order to even think about it.
Yesterday, I posted about the girls, kidnapped in Nigeria by the Islamic extremist group, Boko Haram.
Boko Haram has limited objectives, that don’t involve the entire world. They want their own Islamic state, based on Sharia Law. (If I were the rest of Nigeria, I might give it to them, to have some peace and quiet).
Obviously if attacked, you fight back, but if you want to be the aggressor, you might want to think twice, maybe more.