Humans tend to equate the end of the era of human domination with the end of the world itself. That's so cute. The planet existed for billions of years without us and will probably continue to orbit and support life long after we have knocked ourselves off our own pedestal and broken it up so we can throw the pieces at each other.
After World War II, legend has it that there was widespread support for the idea of a world without war. The one just ended had killed enough people and damaged enough real estate to make many survivors believe we could no longer accept armed conflict as a way to settle intellectual disputes.
Of course we continued to have wars. We just did not let them get out of hand. They tended to be inconclusive and unsatisfying, no matter how savage and bloody they may have been in their own theaters, and how divisive they might have been on the home front.
Against the backdrop of the Cold War it was easy to believe in Armageddon as a conflict between two political philosophies in control of discrete and contiguous land masses. It would be the conventional war of the past, scrawled immensely with enormous weapons. Probably no one would survive.
As the collapse of the Soviet Union demonstrated, preparing for Armageddon is not very economical. You have to have a balance of trade that supports your militaristic expansionism. Merely being armed and dangerous is nowhere near as effective as being rich and ruthless.
In the late 1990s the threat of superpower conflict seemed to have been banished forever. Indeed, this may be true. In the 20th Century we had the incorrectly named War to End All War. In the 21st Century we have the Wars That Can Never End. There's the one between corporate capitalism and Islamic radicalism. There are internal struggles and international chafe areas all over the world.
Separatism is the new nationalism. Dissolution has replaced unification. It's more important to refuse to lose an argument than it is to solve a human problem. Anyone, anywhere, might suddenly find themselves standing next to a suicide bomber. It doesn't happen often in some places, but there's really no reason it couldn't. Because you can't do anything about it, you can't worry about it. If someone is so pissed off at the world that they're going to flip out and kill a bunch of people you can't guarantee to stop them without completely abandoning civil liberties and making everybody go around naked under surveillance cameras. Even then, someone at some level will be wearing pants and giving orders. Or maybe a shirt and no pants. Our leader could be an exhibitionist.
Watching news coverage of the Islamic State and other thinly veiled excuses to commit murder, you can see the logic and the economy of small-scale conflict spread over a widening area. Because it travels on ideas rather than an advancing front of conquered and assimilated territory, a battle of sorts can break out anywhere one or more interested parties can equip themselves with cheap and available materials to spread a little bloodshed. Once people thrust away the idea of living in peace the logical result is fighting.
The people who like to fight and the people who like to watch them accuse anyone who speaks against it of being chicken. Don't think we should fight? You must be a coward. Right. Because those are the only two choices: warrior or coward. It's typical lazy binary thinking, to which humans are subject everywhere.
This would seem to imply a sort of unity among the warriors against the cowards. But the warriors need enemies to fight, not just weaklings to exterminate. Among both the peaceniks and the fighters, factions argue. In the peace camp the arguments just get bitchy. The warriors declare each other enemies and have another war. The result is fragmentation of both sides into smaller pieces that don't get along. The armed and dangerous crowd, often manipulated by the rich and ruthless, battle wherever they can. The bitchy arguments of the peace promoters get very bitchy indeed. Unkind things are said. It's very painful. It becomes very hard to put together a guest list for a party.
The conflict that brings down civilization and returns humanity to scrounging for food in a harsh landscape will not be the spectacular exchange of nuclear missiles, although someone may manage to get a few nukes mixed in. It will be more and more little bombs, rockets, bullets, clubs, knives, kidnappings, beheadings, torture, maiming, IEDs, rocks, bottles, here, there and everywhere. It will be one failed state after another. It will be breakaway republics reabsorbed by their old imperial masters, festering with armed resistance to both independence and absorption. It will be fighting for the sake of fighting, just to prove we can take it.
Maybe we'll burn out the fighting urge before it takes everything down. It seems doubtful at this point, but you never know. What fuels it now is the sense in so many people's minds that they could be the winner that takes all. So put together a band of fighters and start your campaign. Imagine your own Thousand Year Reich, or whatever your culture likes to call that empire of power and control so dear to the grandiose. Or maybe you envision a rational anarchy in which liberated people live in perfect individualistic harmony without paying any taxes to a stupid, intrusive government. Or maybe theocracy is your bag. Your group of true believers will create the nation favored by God to rule the planet. Unfortunately, just a few miles away, a similar group has formed. Take up your weapons. The first glorious battle is upon us. It certainly won't be the last.
Any survivors of this global conflict probably will be no wiser. They'll just be hungrier, more weather-beaten and less well armed. Some of them may be the kind of cowards who talk about living in peace, but we've seen how little traction that has. It will just be a whining noise in the background.