The author's contention is that the trend towards unification and globalization (as seen from the 50's) has allowed bigger pools of power to collect. This in turn has weakened nations in proximity to the powerful ones. Because of that, they are "easier pickings" and do not present the same deterrence to what he considers the inevitable aggressiveness of humans and powerful organizations. That's his reasoning for WWI, WWII etc. - more destructive power due to scale.