This is one of the key reasons why I believe in socialism and a more level class system; pretty much every war, every battle has been in the name of greed for an upper class, greed for land, greed for resources, greed for money, greed for lavish lifestyles. It's the poor who suffer, the ones who actually fight these battles likely don't even truly know why they're fighting them. In a level class system, this greed would at least decline since the incentive would decay.
Ultimately, wars will eventually fade away. That could be a century from now, a millennium, or even more. It will happen eventually but people need to start being politically savvy and realise their leaders are almost always there for themselves.