In this setting, international treaties restrict the yield of legally usable nuclear weapons to under the equivalent of 1,000 metric tons of TNT (one kiloton). If an entity detonates nuclear warheads of a higher yield, it is subject to annihilation via every other geopolitical entity's strategic-level nuclear weapons. In other words, the use of nuclear weapons with a yield of more than 1 kiloton is illegal unless they're being used on an entity who launched such weapons first.

As such, warfare in this setting involves lots of small nuclear detonations. For instance:

  • Why fire 40-50 salvos from a divisional-level conventional artillery park when you can instead fire a single Davy Crockett for the same effect?

  • Why do your tanks need to make direct hits the enemy's tanks when they can instead shoot near them with a 72-ton-TNT-yield nuclear artillery shell? NUKEMAP says an explosion of that magnitude would be enough to destroy a tank within 90 meters/295 feet of the epicenter of the detonation, assuming that 20 PSI of overpressure can destroy a tank - which I'm quite sure it can, considering that half that can "severely damage reinforced concrete buildings".

  • Why put advanced, expensive guidance and aiming systems onboard your air-to-air missiles when you can throw an unguided nuclear air-to-air rocket at your opponent instead?

"To hell with the fallout! To hell with the environment!", these people think. "We have a war to win."

Within a certain time period in this setting, some cities are getting constantly pasted with nuclear weapons. They're pretty small nuclear weapons, to be sure; assume that each of them has a yield equivalent to 10 tons of TNT - think the Special Atomic Demolition Munition's lowest yield. However, this makes them easy to mass-produce and launch, and, for the purposes of this question, let's assume that every 15 square kilometers of a city get hit with one such nuclear weapon per day, and that every city/town smaller than 30 square kilometers gets hit with one such nuclear weapon per day.

Keep in mind that, according - again - to NUKEMAP, a ten-ton surface burst results in effects such as:

  • A 20-meter-across fireball, in which everything is annihilated and kicked up as fallout.

  • 20 PSI of overpressure at 50 meters from the epicenter of the detonation - enough to destroy heavily-built concrete buildings.

  • 5 PSI of overpressure at 100 meters from the epicenter of the detonation - enough to kill people by crushing their alveoli, if I recall correctly.

  • 1,000,000 rem of ionizing radiation at 20 meters from the epicenter of the detonation, assuming that nothing blocks it; I don't know what this'll do to a human, but I assume that it'll turn them into a puddle, if the 200 PSI of overpressure doesn't do it first.

  • 10,000 rem of ionizing radiation at 150 meters from the epicenter of the detonation, assuming that nothing blocks it; I also don't know what this'll do to a human, but I assume that it'll turn them into a puddle in a somewhat slower fashion, considering that Hisashi Ouchi (look him up at your own risk) was hit with about 17% of it and still died horrifically.

  • 100 rem of ionizing radiation at 570 meters from the epicenter of the detonation, assuming that nothing blocks it; results in mild radiation sickness, vomiting, diarrhea, fatigue, etc.

  • 1 rem of ionizing radiation at 1,350 meters from the epicenter of the detonation, assuming that nothing blocks it; this is 80% of what's allowed for a nuclear worker during a calendar quarter, according to OSHA.

  • Some radius at which the heat is enough to set materials such as dried wood on fire - note that NUKEMAP doesn't do this for low enough yields

  • Some level of fallout, which, again, NUKEMAP won't display, since this detonation is 100 times smaller than the minimum it'll spit out a fallout cloud estimate for.

This is pretty bad.

However, you can't just bury everyone in a bunker. There are issues with that - too many to list here, but primarily related to things such as supply constraints and mental health. Assume that making a city solely out of bunkers is not an option for this question. Moreover, assume that you can't just leave.

With that out of the way, the question: in terms of urban design, how do you design a city to be habitable/livable as possible under a daily rain of 10-ton nuclear warheads?

Assume that we're using modern technology, and that this is on Earth - i.e. oxygen-nitrogen atmosphere, carbon-based life, et cetera.

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    $\begingroup$ I think your question is an oxymoron: something designed to be livable under constant attack is not called an urban area, is called a fortress and is made of bunkers. $\endgroup$
    – L.Dutch
    Dec 25, 2021 at 5:41
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    $\begingroup$ @L.Dutch In that case, this is an urban fortress. $\endgroup$
    Dec 25, 2021 at 5:49
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    $\begingroup$ Why is the attacker continuing a constant bombardment when it clearly isn't working? Why not, for instance, switch to attacking the (presumably unshielded) farms supplying these indestructible cities? $\endgroup$
    – Cadence
    Dec 25, 2021 at 7:15
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    $\begingroup$ frame challenge: whoever is being attacked gets wise to this loophole and it's quickly closed as nobody likes getting nuked with a 20 ton warhead every day by somebody who thinks they can just get away with it because it's technically not illegal. $\endgroup$
    – Michael
    Dec 26, 2021 at 1:27

3 Answers 3


Your problem will solve itself

You state that not the whole city can be made out of bunkers. That means you need to have some urban sprawl that allows the rest of the people to live. The nuclear attacks are too frequent versus the slow rebuilding process. That means you can design cities and such to mitigate some damage, but in the end everything will be blasted to rubble. Only the bunkers remain. Then you have a city you didn't want, but it does survive after a fashion.

Mitigating damage

To still give a way to reduce damage to the city in urban sprawl we can look at what survives. The nukes on Japan showed that concrete at a distance has an ok survivability. It is also used pretty lavishly for nuclear bunkers. Concrete is a relatively cheap and easy material for building, so your urban sprawl will be a concrete jungle.

Next is the shape. Balls are great shapes. Lowest amount of surface area for their volume. In addition, the shape more easily deflects energies that strike it. Any energy deflected is energy that isn't used for destruction. Furthermore the shape allows the concrete to absorb the energy that goes into the concrete better. Radiation is also absorbed by concrete. Not the best, as things like lead or water are better, but still good. True balls are unstable, so half a ball or dome is best. You might still need some supports on the inside to keep the dome stable, depending on the size. This can also prevent a lot of the PSI problems. Besides the deflection and such the building can't topple.

This would mean you have a city of many small concrete domes, each with incredibly thick walls. People stay inside the domes at all times, as they are connected with to each other.

To further aid the city you might want to put up really big spikes or something so the nukes hit that instead of a dome.

As stated in the first part, this will only help a city survive longer. Any hit can remove part of a dome. If a part of a dome is removed you need to have it repaired before the next one hits. With the law of big numbers this is statistically improbable, as a nuke will sometimes hit faster that one day in relatively the same place. Maybe even more.


It does sound awfully a lot like bunkers. Maybe there is a side that is hit most, allowing you to put up windows or something on the other side. But the gist here is that you would neither want to or can live in a city under constant bombard of nuclear weapons. Even in bunkers you probably don't want to be there. If the bunkers are above ground the nukes will eventually get through. Especially if they have bunker buster or burrowing kinds. Smaller area, but a lot more destructive power is used.


Fortunately for your population, low-yield nuclear weapons are not remotely cost-effective. You've probably heard of the concept of "critical mass," which is the amount of highly-enriched uranium or plutonium that you need to start a nuclear explosion. That mass does not depend on the size of the explosion you're trying to set off. This is counter-intuitive, but true.

A ten-tonne yield nuclear weapon needs as much HEU or plute as a 25Kt weapon - likely more, actually, since physically small nuclear weapons can't compress their cores as well as normal-sized ones. So 25Kt of yield can be obtained with one bomb's worth of material, as a single explosion, or with more than 2,500 bomb's worth of material as 2,500 10t explosions. Since the HEU or plute are the expensive components of a nuclear weapon, the economics are prohibitive.

"But," you ask, "why was Davy Crockett built at all, if it's so inefficient?" The answer is "intra-service rivalry," if one branch of the US Army was going to have nukes, all of the other branches wanted to have them too. The infantry needed very low-yield weapons, to avoid killing themselves when they were used at short range; the range was short because weapons infantry can carry can't fire a warhead very far. Few Davy Crocketts were built, and they were retired quite swiftly.

If you can make Davy Crocketts, you can make more powerful nuclear weapons, and it's actually easier. Limiting Davy Crockett to 20t required making sure that the nuclear explosion fizzled rather than going off "properly" and this is not entirely reliable. Some of them might well have yielded 100t or 200t, unpredictably. This is unlikely to cause your arms limitation rules to be detectably broken, because it's quite hard to remotely determine the exact yield of a low-powered nuclear weapon at a distance, and there are substantial margins of error in such a determination.

So your scenario is not remotely plausible. In fact, it's pretty amusing to anyone who knows a bit about nuclear weapons.

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    $\begingroup$ "Critical mass" is a misnomer; what really matters is critical density. (Well, actually, critical neutron impact cross-section, but density is much easier to say.) You can cause a sub-critical mass to go critical by compressing it. It's a deeply implausible scenario for any number of reasons but its nuclear physics is hardly the worst offender. $\endgroup$
    – Cadence
    Dec 25, 2021 at 23:21
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    $\begingroup$ @Cadence What really matters is the chance a neutron hits a fissile atom. That is both a function of density (reduces the chance it goes between atoms) and mass (more atoms in it's path to hit.) Note that causing detonation by compression isn't implausible--look at a Teller-Ulam H--bomb design. In addition to the trigger there's a separate plutonium rod inside the lithium deutride. It's compressed by the fury of the nuclear detonation inches away and detonates, setting off the now-compressed lithium deutride. $\endgroup$ Dec 26, 2021 at 3:52

Not arguing the scenario. It is as given.

Behold the city.

mark twain natonal forest

The city is 1.5 million acres, or 6070 square km. You mandate that a little nuke hits somewhere in a 15 square km area every day. This nuke produces a 20 meter fireball so let us say each hit wipes clean a 100 square meter area. Multiplied by 364 (they take september 26 off) that is 36400 square meters eliminated in a year or 0.0364 square km. Thus at the end of the year a 15 km area still has 14.936 square km that has not been wipde clean. That is 99.5%. That is assuming the nukes land at random because this seems like that kind of a deal.

Let us say 100 people reside per square km. 0.5 of those people will die from a nuclear hit each year or 500/100,000 people. If 2 people reside per square km the mortality from nukes is 5 /100,000 people. The yearly death rate in the US from traffic accidents is 12 / 100,000 people. Recall you have 6070 square km to work with. That is a population of 12140. The population of Pierre, capitol city of South Dakota is 13961. "But but but but" the commenters sputter! "But can a whole country live this way?" The US has 900,000 square km to work with and 300 million people, so it would be 333 people per square km and 1.65 dead from nukes each year per 100,000. Covid killed 200-300 persons per 100,000 since the pandemic - 2 orders of magnitude more deadly than puny nukes.

My sleeping quarters in the Mark Twain Forest City will be like a hobbit house to ward off stray rays in case there is a nearby hit. I will have a fine garden and a woodburning stove.

Is it still a city if it is so decentralized? You can call it what you want. In the many nukes scenario you propose, would people like to live spread out and work by radio and bike commute? It sounds OK to me.

bunker city


  • $\begingroup$ Yeah +1 I'm afraid you're right.. It looks like an apocalyptic scenery... It will take you a year to die in one of these. And if you ever attempt to stick your nose outside, all these folks have weapons.. don't count on humanity in these circumstances. $\endgroup$
    – Goodies
    Dec 25, 2021 at 23:14

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