In near future a global war wipes out most of humanity, leaving only a handful of survivors. Thousands of years later these survivors have adapted to lives in small pockets of the world still left undestroyed.

Here's the deal: big part of the story is the fact there is something that prevents the people from leaving these pockets, and story theme-wise it must be something that's caused by the past warfare. Only to my understanding there are hardly weapons that would actually contaminate or ruin the earth to the extent I want to portray in the story.

Here's the question: what kind of speculative weapon of mass destruction would leave such a big, possibly toxic impact it would still affect people in target areas even after thousands of years? A weapon that would make resettling the affected areas near impossible even far into future. Does such a weapon exist? Could you imagine a weapon that fits the criteria with near-future technology?

Thanks for all the ideas in advance. Bonus points for stretching the limits of reality as little as possible.

  • $\begingroup$ Are you open to social consequences, rather than strictly physical ones? A sufficiently damaging weapon could cause social forces which have the effects you want. $\endgroup$ Feb 22, 2018 at 3:27
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    $\begingroup$ But not radiation? Because that's the obvious answer. $\endgroup$
    – rek
    Feb 22, 2018 at 3:58
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    $\begingroup$ You could turn the idea on its head. The survivors are trapped in their small pockets of the world by, for example, force-fields that protected against the weapons of mass destruction used in the war. $\endgroup$
    – a4android
    Feb 22, 2018 at 4:02
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    $\begingroup$ When 'prevents the people from leaving these pockets' do you slow death if you stay out too long, instant death depending on your luck, or 'go to hell, go directly to hell, do not pass go, no saving throw'? $\endgroup$ Feb 22, 2018 at 5:07
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    $\begingroup$ @a4android: Please don't encourage people to use "force fields" as explanations. They're far too often an excuse for lazy handwaving. $\endgroup$
    – nzaman
    Feb 22, 2018 at 13:38

11 Answers 11


This answer proposes an alternative concept to speculative weapons of mass destruction. The global war was fought by armies of autonomous military systems and weapons platforms. Basically, "killer robots". This killed the majority of the world's population.

However, there were small regions where the killer robots were excluded from taking lethal action against human beings and their resources. The reasons for these exclusion zones can be left as an exercise for the OP.

Thousands of years later the killer robots are still out there. Humans survive in their small enclaves.

By the way, killer robots can include orbital weapons platforms armed with laser-weapons and the dreaded "rods from the gods". This can accompany flights of drones patrolling the skies and armoured death machines trundling across the landscape.

This scenario assumes that the world and its major nations have all adopted killer robot types of military systems. At some point conflict breaks out and the killer robots become an unstoppable force waging war on a global scale. This leads to an inevitable collapse of civilization. Only small enclaves of survivors remain.

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    $\begingroup$ For the killer robots to last thousands of years, there will need to be an automated infrastructure in place that can repair and make new killer robots. If the killer robots can setup new automated infrastructure then they can expand into any country that did not adopt them. $\endgroup$
    – Anketam
    Feb 22, 2018 at 11:26
  • $\begingroup$ @Anketam Of course! I assumed anyone looking at my answer would assume that had to be the case. The survival enclaves are most probably the result of blind spots in their programmed war plans. $\endgroup$
    – a4android
    Feb 22, 2018 at 11:57
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    $\begingroup$ So THAT'S Elon Musk's end game with SpaceX! $\endgroup$
    – Dark Hippo
    Feb 22, 2018 at 12:16
  • $\begingroup$ There are a lot of parallels between this answer and Horizon: Zero Dawn. $\endgroup$
    – Frostfyre
    Feb 22, 2018 at 13:20
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    $\begingroup$ alternatively what if the safe zones are the robotic maintenance and assembly areas where the robots have established themselves as overlords and using the human population as their labor force, they don't care what the humans do as long as they don't try to escape and they perform their quota of work $\endgroup$
    – BKlassen
    Feb 22, 2018 at 15:10

Rather than use kinetic energy or radiation to destroy their enemies, the scientists working for the various powers began using genetic engineering to create bioweapons. Plagues and amped up versions of killer virus were considered, but rejected due to the impossibility of containing the effects.

The solution was brilliant: use genetic engineering to modify crop plants so the people in that nation would not be able to digest them or extract nutrition. Virus were prepared and various vectors selected and then released on enemy nations. Billions of people starved, economies collapsed and nations fell. Of course, the hubris which drove the victors to choose such a fiendish method of attack failed to protect them, the vectors and virus mutated and attacked their crops, leaving the victory as ashes as their nation starved to death as well. The calamity spread, and soon most human life and activity ceased.

A few humans here and there were able to survive on stored food, carefully preserved green houses sheltering uninfected plants or changing their diets in radical ways.

Of course, the mutations which made food crops impossible to eat were expensive in terms of maintaining them, and many plants began to throw them off. Other mutations also took hold, so the killer virus ran its course and eventually only surfaces in small outbreaks from time to time. The descendants of the humans who survived the war have also changed. They live in small bands foraging the wilds. Many have taken up unconventional diets eating plants which their ancestors would not have considered. Others have become very sensitive to the differences between lethal mutated plants and the ancestral versions which are edible, and some have, through evolution, become able to eat the mutated crop plants which killed their ancestors.

Since the majority of the plant species are no longer edible to humans, or are of much more limited use for human digestion, the world is a literal food desert for the vast majority of the survivors, and the ability to sustain large human populations no longer exists.


Some sort of cloud seeding system, perhaps involving nanotechnology deployed from orbit, whichever side was losing the war implemented this system to cause the economic collapse of their enemy. With rain only occurring at sea the world's ecology collapses, lakes dry up, rivers stop flowing, humanity can only exist by depending upon desalination and artificial irrigation. People can venture into the deserts to loot the abandoned towns and cities but they can't stay there, they need to return to the infrastructure on the coasts to restock food and water.


Unravelling God's stitches.

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After the war, the rebuilders needed energy. The old sources were exhausted. But there is energy at interfaces, and it was discovered that a small hole made in the walls between dimensions could allow energy to flow from one state to the next in nearly unlimited amounts.

It turns out these were load bearing walls. The holes grew and reality began to shift, or fold, or warp one dimension into / onto / over the next. Physical laws became unpredictable, or cancelled each other out. One could easily get lost - or changed - in altered realities juxtaposed onto ours. Beings from other planes could wander into ours - aliens, lost gods, monsters from the outer dark. Ghosts. Spores. Loads of bugs.

Celestial fixers - angry angels - arrived and planted reality anchors to contain the damage from spreading to all of Creation. Their intent was not to preserve what was left of humanity but that was a byproduct - around these anchors the survivors huddle, watching for what might emerge from the shifting planes outside their borders.

This would be a fine setting for a story because maybe the new shifting reality has its own rules. Can humanity make the ultimate adaptation?

If you must have the trouble be the end result of a weapon certainly you could weaponize the ability to make interdimensional rifts.

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    $\begingroup$ A fantastic concept! I suggest you write the story to go with it. I'd line up to buy a copy. $\endgroup$
    – a4android
    Feb 24, 2018 at 0:48


Forget about nukes and diseases, if you to really kill people, their pets, their homes, and the very land where they stand you could use geo-enginnering as a weapon of mass destruction!

The easiest way would be to use certain compounds to obscure the atmosphere in the hopes of lowering the global temperature, but if that gets out of hand you could have the entire Earth drowned into an Ice Age.

The pockets of survivors could be centered around certain zones that thanks to some geographical disposition has managed to remain warm enough to sustain a small population.


Maybe turn it around. Something holds them to those areas.

There was a virus that implanted a mutation that caused people to become reliant to a toxin. Maybe it was a defensive measure to resist a toxic weapon (with plans to use a second virus to remove that mutation). Maybe it was to allow people to survive in a polluted world. The dependency was a side affect of being able to survive that toxin.

The infrastructure to create or distribute the reversal virus has been lost in that or another upheaval.

This allowed people to survive when the planet was polluted. However, nothing lasts forever and the toxin/pollution has been breaking down. The areas with enough toxin to live in have been getting smaller and smaller. Now there are only a few pockets remaining that are polluted enough for the people to live in. Good news for the planet, bad news for the people.

They can now send out expeditions to find ways of re-poisoning the planet or try to find the reversal virus.

Now, the mutant hoard (from all the 80s bad post-apocalyptic movies) that wants to re-pollute the planet are the good guys.


Virii change over time, but chemicals stay the same.

OK, massive oversimplification, but here we go.

A Bioweapon like a virus could prove too difficult to contain, and may well mutate beyond the bounds the creators had in mind. However, a nerve agent may stay lethal for a very long time, and it won't move about.

VX nerve agent has been around for a long time. It's oily, pools into low lying areas. It's not water soluble, and it won't wash away as easily. It takes high heat to turn to a vapor. It can contaminate a site for years. VX may not serve your purpose directly, but this nasty crap actually exists TODAY.

Come up with a more lethal toxin with very similar characteristics, then have some madman in the past use it widely. Natural boundaries like mountains will help contain it. High altitude communities might fare better because the crap will sink down kind of naturally. Given that this stuff is mostly non reactive, it will break down very slowly.

Your communities that survive are going to reach equilibrium with their surroundings, limiting populations based on the productivity of the un-contaminated land. Travel from one community to the next is going to be dangerous as heck, so it won't happen much.

I don't think its a stretch for this stuff to keep populations contained for 1000 plus years after the initial massive die off. If this stuff targets animals rather than plants, actions like erosion are going to be less of a problem for spreading it about. If it kills everything, the east coast of the US is doomed after plant life in the plains dies out.


In a supposed report regarding how rapidly changing technology could render current methods and weaponry obsolete (supposedly) authored by NASA (More on that later) I remember reading about "Programmable area denial nanite swarms." This weapon is basically a nanite swarm that is programmed to settle over a massive area (we're talking entire regions of countryside) and be capable of recognizing any human signature not equipped with the proper IFF signature to do a number of aggressive actions against the target. Several methods were discussed, one of which involved explosive nanites that can combine and detonate upon detecting a threat scaling the blast to the size of the target. Another was that the nanites could simply be highly abrasive "smart dust" that detects an intruder and fluffs itself from the soil into a dust cloud that could dig into lung tissue and kill the intruder.

The report was later found to have been authored as a hoax to support a conspiracy theorist's blog but it still has some pretty good ideas for exotic super-weapons that seem to posses the properties that might be useful to your plot setting. The whole thing is interesting, even if it is a hoax. The particular stuff you want to see starts at page 40. http://www.stopthecrime.net/docs/nasa-thefutureof-war.pdf

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    $\begingroup$ The nanite swarm needs a power source. That is the biggest hole in most nanite stories. $\endgroup$
    – ShadoCat
    Feb 23, 2018 at 19:30
  • $\begingroup$ @ShadoCat I mean the powersource could be a microscopic betavoltaic battery that lasts for a hundred years. $\endgroup$
    – Efialtes
    Mar 13, 2019 at 22:46

What kind of speculative weapon of mass destruction would leave such a big, possibly toxic impact it would still affect people in target areas even after thousands of years? A weapon that would make resettling the affected areas near impossible even far into future. Does such a weapon exist? Could you imagine a weapon that fits the criteria with near-future technology?

"Second-Variety" type of semi-biological killerbots.

These would be a terror weapon designed for very long term area denial against unhardened targets (houses, villages, etc., but not army bases). They would be self-replacing, which means they're more like living organisms themselves: there are larger "mothers" that spawn hunting-optimized units. Photosynthetic, and able to recognize a large, warm organism and attack it, probably using some kind of neurotoxin; also, they can oxidize most organic matter to harvest energy. Organic matter is also brought back to the mothers to assemble more bots.

They were initially used as portable, reusable mine-fields (to go through a bot infested zone you need reasonably high technology, and this makes you detectable with other means).

As for why they don't penetrate into habitable "pockets", there are lots of possibilities (and you aren't limited to only one).

  • by design. Some areas were classified "off limits" and the bots still obey these limitations (which begs the question, do they have GPS? How do they know where a certain area even begins? Do they rely on some kind of emission? If so, could such a protective emission dwindle in time?).

  • by chance. The bots aren't hardened and cannot e.g. swim or climb steep walls. So several geographic features may conspire to create safe havens, or thwart their hunting mechanisms (they might hunt by smell, or IR, or electric sense).

  • by accident. Whoever programmed the bots inserted several time-saving, power-saving tricks to improve performance and concentrate the bots on more promising hunts. And they made mistakes. As a result, for example, the bots mistakenly consider human life impossible based on absolute, not partial oxygen pressure; therefore, they will never venture beyond 1500 m above sea level, for their programming guarantees there can't be anything worth hunting there. The safe havens are mountain-top "islands", while plains are kill zones.


I'd go with a bio-weapon.

A decomposing fungus was engineered to produce high-persistence non-selective herbicides. You spread it to an area, it kills the plants using the already dead plants for energy. Then your enemy has no agriculture and either starves or buys food from you. Simple and brilliant.

Or as it turns out, the enemy may simply collapse creating a huge influx of refugees into your area. Refugees that spread with them your bio-weapon wherever they go. Bio-weapon now doubly brilliant as the enemies efforts to kill it had provided it with resistance to all fungicides known to science, including the one you had specifically engineered it to be vulnerable to as a safe guard.

You fungus becomes a global phenomenon killing plants world wide almost faster than your agents can cleanse evidence of you ever having had anything to do with "the plague". Fortunately people are too preoccupied fighting over the remaining food stocks and fishing fleets to investigate. Dying from starvation is pretty good distraction too.

You start thinking about the ways you can turn this to your advantage. With so many people dead and so much agriculture lost, the world will be redrawn. This is a huge opportunity to anyone with some initiative and enough common sense not to waste resources trying to save people who cannot be saved. You start to think this was a blessing. Maybe your subconscious was able to see farther ahead? Maybe ruling the world is not your ambition but your destiny?

Then things start to go wrong. With plants dying all over erosion accelerates. Huge amounts of top soil is carried to the oceans by wind and water. At which point we find out that the herbicides produced by the fungi can kill most forms of algae if there is enough of them. And there is.

Not enough to seriously threaten the algae themselves, mind you. But combined with combined with starving people fishing all they can, the sudden collapse of the algae pretty much wipes out the fish from the ocean as a viable food source.

And things keep getting worse. Turns out that if you kill enough plants they turn less carbon dioxide to sugars and oxygen. And that poisoned plants and starved animals release carbon dioxide to atmosphere as they decay. The greenhouse effect gets a huge and rapid boost.

The surviving people mostly just shrug their shoulders in response to this. Does it really matter any more? Turns out it does. The increased temperature creates torrential rains and huge arid areas. With most terrestrial plants dead, the erosion accelerates to speeds never seen before.

Thanks to high persistence herbicides in the soil and high levels of carbon dioxide persisting this goes on for centuries. Apart from few isolated pockets the top soil is lost and the landscapes become barren and arid.

But there is good news, those herbicides took lots of energy to produce so the fungi evolved not to bother after few decades. And most spores of the old strain died after few centuries, as well. Problem solved.

Marine life rebound after a century as well. Even the stablest poisons became safely embedded in the sediments and algae recovered completely. The fish more than recovered. With the most people dead and even the survivors unable to really build ships, humans no longer are a threat to fish flourishing.


Trapped on small islands

The survivors are trapped on small and remote islands without any trees left. So they can sustain themselves, but never build boats to get off their islands and colonialise other parts of the world.

There is a precedent in our world: The Easter islanders deforested their remote island and were trapped on it until the Spaniards rediscovered the island.

Note that this answer does not require a persistent weapon of mass destruction. Once the damage is done (deforested islands) it is enough to confine the residual population in their place.


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