From a recent Hacker News comment by me that was both popular and controversial, in response to the declining fertility levels, declining interest in family, and projected downturn in Asia -
I have a theory that I haven't found expounded before. It came from a combination of travel through 60+ countries, living and working and interacting with local people on a pretty intimate level sometimes, and study of lots of history.
It's going to be controversial and maybe even shocking, so brace yourself for a moment before reacting please.
I think peaceful societies self-destruct.
With a few notable exceptions that require a geography suitable to isolationism, long term peace has historically been achieved through your country or one of your ally's having military supremacy over the rest of your neighbors.