The real culprit of our boring times is of course true weapons of mass destruction.
Every country with major nuclear arsenal can inflict a terrible toll on any single opponent, even as a weapon of last measure. Not to mention most industrial countries could have nuclear weapons in relatively short term if it was felt as necessary for national survival.
So the nuclear powers of our time, Russia, USA, China, France, UK, Israel, India and Pakistan are practically off limits for having their heartland invaded by conventional warfare. North Korea would really like to join the club too and they also have their own ballistic missile program.. Then there's Iran which wants the bomb to keep from being "liberated". Japan is also making noises WRT north korean nukes and so on and so on.
You _cannot_ have multi-year war between industrial countries without nuclear holocaust entering the equation anymore. cf mutually assured destruction doctrine for what I'm talking about. Do not have ballistic missiles? Well, just get some proxy company to ship your bloody nuke in a shipping container to the target..
So mostly we see terrible drawn out conflicts such as ethiopia - etitrea war between countries without industrial backbone to really churn out war material en masse.
And in any case, say whatever you want but EU is our last, best hope for peace in multicultural europe..