I don't think we will have another war between any two developed nations. The triumph of capitalism has meant that we now have global markets, big companies are now multinational, and all of the big economies are intertwined. A big country can't really start a war with another without causing huge damage to its own economy. Indeed multinational corporations are now so powerful that countries are effectively in thrall to them. Look for example at Ireland prostituting itself to Amazon so that it could be the Amazon base in Europe. Capitalism causes a lot of problems, and it does create wars - like the Gulf War oil grab - but one thing in its favour is I think that it prevents wars between big countries.