[GoNative]

You don't even need different backgrounds. During feudal times in Japan they fought amongst each other all the time. All you really need for war is men (mostly) to be in charge of things and greed. Greed is the basis for almost every war in history. Many have been waged in the name of religion or nationalism but this is generally just to get the ignorant masses on board with the cause. The root of most conflicts is purely and simply greed. And last time I checked greed was alive and well and almost encouraged in most societies. Hard to imagine there'll ever be a time when there will be no conflicts at all on this planet.