I know this a very unrealistic question but imagine in a alternate world where scientists and engineers don't have the resources or the requirements to make nuclear weapons, what type of weaponry could replace it? Do humans stick to conventional wars or do people just make more powerful bombs but it's doesn't have the power that nukes have?

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    $\begingroup$ N is only one letter in an NBC war. (the other two are Biological and Chemical) $\endgroup$
    – Allan
    Jul 5 at 23:47
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    $\begingroup$ This question is pretty well answered at this point, but as a theme, the thing that would replace nuclear weapons is another weapon against which there is no defense. Biological or chemical weapons can fill that gap, as suggested, or more powerful incendiary weapons (Hamburg didn't need a nuke). $\endgroup$
    – jdunlop
    Jul 6 at 0:29
  • $\begingroup$ Under what geopolitical circumstances? Why would they bother making any weapons beyond what they have if there's a nothing more than a mild/moderate threat of aggression - or none at all? Or, why would they not surrender like Italy in WW2 despite having a well-equipped and trained army? What's the politics of this here - without specific context this is too broad and opinion-based. $\endgroup$ Jul 6 at 7:09
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    $\begingroup$ Chemical weapons won't work, but conventional weapons are also destructive and expensive enough that deterrence can still at least partially work. Wars are still more likely in general, but they are also becoming less likely even among nations without nuclear weapons in our world. $\endgroup$ Jul 6 at 8:14
  • $\begingroup$ Firebombing Dresden : "22,700–25,000 killed." Tokyo : "estimated 100,000 civilians dead." Hiroshima and Nagasaki : "The two bombings killed between 129,000 and 226,000 people" - if you want to replace those two bombers with their one bomb each, you need more like 325 bombers to deliver over 2000 tons of ordinance (Tokyo). It's only a question of how many zeros are in your checkbook and how absolutely freaking done with this BS that you are. $\endgroup$
    – Mazura
    Jul 6 at 11:29

14 Answers 14


The Earthquake Bomb:

This was already being developed at the end of WW2, and partly made redundant by the advent of nuclear weapons. The idea was to make as big of a bomb as possible, drop it from as high as possible, as fast as possible, penetrate as deep as possible, and cause a huge shockwave that destroyed everything in the area, not just things hit by the bomb itself.

Nuclear bombs did not STOP development of the earthquake bomb, although it did play a smaller role than it likely would have. The current big boy is the massive ordnance penetrator at 30,000 lb.

Burn The Skies:

Similar in function on the surface are thermobaric bombs, which cause airborne shockwaves to induce huge amounts of collateral damage and fire. These would likely have been developed on a huge scale to meet the strategic needs to decimate enemy cities and military bases. I'd guess these would have evolved into cluster munitions to blanket large areas.

Similarly, efficient cluster incendiary bombs would likely have been deployed on a massive scale, to cause firestorms like those seen at the end of WW2.

Poison the Land:

Chemical weapons would have the potential to match the destructive capacity of nuclear weapons as well. Deadly neurotoxins like botulinum toxin, could kill millions of people and spread with the winds, devastating huge areas.

Biological weapons like anthrax could be used similarly to the threat of radiation to render areas uninhabitable. They could annihilate enemy crops and cause mass death through starvation.

All these weapons would likely have been adapted to really large ICBM's to allow powers to threaten each other with instant devastation. The reason more of these weapons AREN'T used is that the horror they entail were dwarfed by nuclear weapons. But in a world without nukes, massive neurotoxin-filled missiles and incendiary weapons would be poised to devastate enemy civilian populations and render military bases uninhabitable.

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    $\begingroup$ Do you think they'd be bad enough to establish deterrence? That's the main geopolitical effect of nukes, great powers avoid wars. $\endgroup$ Jul 6 at 3:30
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    $\begingroup$ "The reason more of these weapons AREN'T used is that the horror they entail were dwarfed by nuclear weapons.". Sadly that is only one part of the truth. The main factor BC weapons were actually banned is that their effects are much less controllable than nuclear weapons. Especially biological ones. For example, you cannot control winds, so an airborn toxine or a patogen can travel back and affect the country that dropped the bomb (much more than nuclear fallout). Moreover, patogen effects are not controllable in the long run. $\endgroup$ Jul 6 at 9:15
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    $\begingroup$ The sad reality is that countries decided that BC weapons aren't strategically or tactically viable in a practical and economical way, so they gave them up by treaties and also pretended to be "the good guys who are against horrible inhuman things". If they were really horrified, there wouldn't be stockpiles of nerve agents ordnance in many (democratic or not) countries. $\endgroup$ Jul 6 at 9:20
  • $\begingroup$ I feel the title of the answer doesn't quite reflect the answer. It's not just the earthquake bomb, it's a bunch of existing technologies that might have been more refined, or developped earlier. $\endgroup$ Jul 7 at 10:43
  • $\begingroup$ @AmiralPatate Fair, a lot of time I would have had a series of title lines for this. "Earthquake bomb" was just the most fun. I'll review. $\endgroup$
    – DWKraus
    Jul 7 at 12:19

Kinetic space bombardment.

Although to achieve effects comparable to the nuclear weapons, the projectiles have to be either too heavy or need to achieve higher speed somehow. For example, an 8t tungsten rod moving at 60km/s speed delivers about $14TJ$ kinetic energy - compared to $88TJ$ of the Fat Man. That means an array of such rods (with steering) in a retrograde Solar orbit is at least at the same order of magnitude as a fleet of our first nukes.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Jul 7 at 16:00
  • $\begingroup$ It is in portrayed towards the end of "GI Joe: Retaliation" the movie... It put this exact idea in use as what the villain launched against London. See the video 50 seconds in on the 2nd trailer. imdb.com/video/vi234137369/?ref_=tt_vi_i_2 $\endgroup$
    – phyatt
    Jul 7 at 20:38
  • $\begingroup$ 8 tonnes of a cheaper metal would do the jobs but be much cheaper to build. IMHO an 8 tonne arrow-shaped lead rod clad in a carbon fibre heat shield would hit the planet largely intact, even at 60km/s. $\endgroup$
    – Bohemian
    Jul 8 at 7:38

There is a practical limit to how large a bang you can make with conventional explosives. A small nuke is equivalent to 10-20 thousand tonnes of TNT, so it is difficult to transport a powerful chemical explosive. In principle you could stuff 300,000 tonnes of high explosive in an oil tanker, and sail it surruptitiously to the target (assuming the target was a port) - but that doesn't seem particularly practical.

So for 'weapons of mass destruction' - stupid humans might revisit chemical warfare - nerve gas etc., or biological warfare - aerasolized anthrax, and the like. Like nukes, they are very unpleasant, indiscriminate in damage caused, and are particularly good at targeting civilian population centres. Do it 'wrong' enough and your humans could stiill create a doomsday scenario (sigh).

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    $\begingroup$ This is fun for non-nuclear. en.wikipedia.org/wiki/Texas_City_disaster $\endgroup$
    – DWKraus
    Jul 7 at 0:24
  • $\begingroup$ @DWKraus for certain values of “fun” $\endgroup$
    – jez
    Jul 7 at 16:45
  • $\begingroup$ @jez Okay, yeah, "fun" is contextual. It was relevant to the answer, though. $\endgroup$
    – DWKraus
    Jul 7 at 17:28

Threaten to build a time machine

OK, this one is highly speculative, and not my original idea. I read it in a short story the author and title of which I have forgotten. The premise was that there is nothing in the laws of Physics to prevent time machines, but it has been determined (by interstellar archaeology) that bad things always overtook every civilisation that attempted to build one. Some sort of cosmological causality protection principle at work.

In the story, a machiavellian dictator tried to influence his opponents into building such a machine before he did (or didn't), because he believed that it would result in catastrophe overtaking them rather than him. He failed to realize that the universe might not have such a well-defined definition of the cause and effect to be protected. Their sun very unexpectedly went nova.

In Stross's "Iron Sunrise" there's a weakly Godlike entity known as the Eschaton. (For quite strong values of "weakly"). It does not appreciate attempts to violate causality because they might threaten the chain of events which led to the technological singularity which created it. So, the consequences of violating causality (or trying to) can be very similar to the above. However, the Eschaton does appear in some sense to care, and therefore tries to prevent such attempts using minimum violence at an early stage. It only occasionally has to destroy a solar system, but that is not entirely unknown.

  • $\begingroup$ So like Terminator. When time travel occurs something happens to wipe the slate clean so paradoxes don't matter in the grand scheme. $\endgroup$
    – DKNguyen
    Jul 6 at 14:30
  • $\begingroup$ Why would a catastrophe involving time travel necessarily happen around the time they were first experimenting with it (unless you invoke something like the Eschaton)? It could literally happen anytime. $\endgroup$ Jul 6 at 15:26
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    $\begingroup$ @CristobolPolychronopolis One variant idea of time-machines is that it would only be able to travel along its own line of existence. So no time machine could go further back in time than the day of its own creation. Such a machine might produce interesting effects if destroyed. Like producing a continous explosion from the when it was created to when it was "destroyed", producing a paradox because it couldn't have been used if it was exploding. Basically a Time machine that is going to be destroyed in the future will self-destruct when you turn it on, violently negating any of its own future. $\endgroup$
    – Ruadhan
    Jul 6 at 15:49

Thermobaric Weapons

Essentially these create an explosive mixture of fuel and air which is then detonated. Apparently it's effective at killing people by rupturing their lungs, so personally I would place it on a similar level to Nuclear weapons on the "places I don't want to be when one goes off" scale.

On the Earth we live on, Wikipedia says

International law does not prohibit the use of thermobaric munitions, fuel-air explosive devices, or vacuum bombs against military targets. Their use against civilian populations may be banned by the United Nations (UN) Convention on Certain Conventional Weapons (CCW). As of February 2022, all past attempts to regulate or restrict thermobaric weapons have failed.

How human-like the inhabitants of the alternative world are in areas such as being aggressive and killing each other is a matter of choice in the world and story you wish to create.


Destruction: WWII weapons already beat nukes

The destruction at Hiroshima wasn't even as bad as other bombing raids at the time, which did not use chemicals (owing to treaty) or bioweapons. The conventional destruction that exceeded nukes was a thousand or so bombers carpet bombing an area with bombs and millions of small bomblets of the explosive type... and then, a "double tap" of incendiary bomblets.

The tiny incendiary bomblets would normally just bounce off the roofs, land in the street, and be easily dealt with by residents and the fire brigade. However the first round of small bombs smashed the roofs, and the large bombs smashed the water mains, so the fires would be inside the buildings and no water to fight them. A percentage of the buildings would be fully engaged, and then spread to adjacent buildings until the city was gone. The best the fire department could do is hold the firestorm at the edge of the bombed area.

Terror: we had that in WWI

You're talking about chemical weapons there. The things were so horrible that they were banned by treaty, and Hitler and Tojo stuck to the treaty and abstained from using them. Of course, both of them were "living in glass houses" because of their urban density, and neither one had any ability to reach the United States. Consider the perspective of the generals as the Doolittle Raiders flew into the sunset... "Those could have been chemical weapons. Let's make sure they are not!"

Far-away breaking stuff:

Now your question has a flaw, in that it does not distinguish nuclear weapons from the imfamous methods of delivering them, notably ballistic missiles.

Ballistic missiles hardly need to be nukes. Imagine you have an ICBM with ten reentry vehicles which can be independently targeted (as long as they are all within a 100 kilometer circle). Each reentry vehicle contains a whole bunch of BLU-108 submunitions. These pop out four "skeets" which flitter down like a maple seed, steering themselves toward a tank or APC. So you become aware of the location of three enemy tank divisions, and launch a single ICBM. It starts raining skeets, and eight minutes later, the enemy has three tank platoons lol.

We can't use weapons like that in our world, because other countries with nuclear weapons will detect the ICBM launch and assume it is a nuke. That would be bad.

But in your world, no one will assume it is a nuke obviously. They will assume it's a weapon like this.

Back to your question, "breaking stuff far away" really depends on whether your society bothers to develop missile technology or not. If you don't, then you're down to bombers, and to achieve nuke-level destruction, you send 800 bombers instead of just one. If you do have missiles, then you invest extra heavily in precision targeting, and put a conventional round right down their stovepipe.

  1. Radioactive (dirty) bombs.

Absent nuclear weapons themselves radioactivity and its effects on plant and animal life was and would still be an active area of study.

So you could have fleets of WW2 era bombers carpet bombing major cities using bombs that were a combination of conventional explosive bombs & the highly refined/particulate radioactive element of your choice. (I believe SF Author Robert Heinemann wrote a short story about this.)

You could have two basic types. One a conventional explosive bomb laced with radioactive element that explodes on impact doing conventional damage and scattering radioactive material around the general area and one a parachute bomb that just floated down and at the appropriate altitude just opened and let it's contents drift downwards in the wind.

  1. Conventional chemical weapons and nerve gases.

At the outbreak of WW2 all major powers had large stockpiles of gas bombs and shells and were preparing their military and civilian populations for the possible use of air dropped gas bombs etc. (They were never used however because all combatants knew their opponents also had these stockpiles and were afraid of retaliation. Which should be familiar. (MAD anyone?)


Directed-energy weapons, preferably delivered from orbit. Since you can

  1. easily scale them both in size and amount (as long as there is free space in orbit),
  2. easily power them (e.g. using solar energy or any other handwavium),
  3. easily target almost anything (worst case scenario you'll have to wait a couple of hours for your planet to rotate if you don't have high enough orbital coverage),
  4. easily evade most of the conventional problems with weapons of such size & power (storage, saboteurs, decomissioning),

I see them as the best worldbuilding replacement.

Example in action here (yeah, the entire episode is like an ad for them).

  • $\begingroup$ Nothing in space is easy. $\endgroup$
    – gerrit
    Jul 6 at 13:41
  • $\begingroup$ @gerrit with enough handwavium, everything is easy. SpaceX is the prime example of this. $\endgroup$
    – spamove
    Jul 6 at 14:01
  • $\begingroup$ What SpaceX does is not easy. $\endgroup$
    – gerrit
    Jul 6 at 14:03
  • $\begingroup$ @gerrit I agree. We've been able to put people on the Moon in 1969. That's 53 years ago. Taking into account the effort done then, just 24 years after a century of wars and famines, and bearing in mind the technology available then, calling what SpaceX does "easy" doesn't seem adequate. "Trivial and facile" is better. $\endgroup$
    – spamove
    Jul 6 at 14:16
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    $\begingroup$ I have to mention that orbiting weapons are quire exposed. If we have space-based lasers that can explode buildings on the surface, we can more easily have surface-based lasers that can explode satellites. $\endgroup$
    – Alexander
    Jul 6 at 18:22

bio warfare

if nukes werent invented, but we still had the tech we do today, a team of scientists could likely invent a super microbe.

the threat of a massive plague sweeping across your nation would likely be a deterrence against something, like we do with nukes.

not only that, all it takes is one person to release it into a city center and then theres the retaliation attack. You might destroy a nation with your own super weapons, but there are still people loyal to that nation who, given time, effort, sneaky business, and numbers, could make their way into a city center and release the microbes.

and its also super dangerous if mishandled!


An artificial meteor.

The "earthquake bomb" is a similar idea, but still has an explosive charge in it. But a different idea has been proposed in the past; bringing large amounts of a heavy metal such as tungsten into orbit, and then payload after payload, bring enough to mass together what is essentially a 20-50,000 ton tungsten "spear" which can be dropped from orbit onto any location on the planet. It could not be stopped, it would be unable to melt during descent due to having a high melting point (thereby retaining its structural integrity), and when it pierced the Earth, the shockwave it would create through the crust would decimate entire nations, followed by a dust cloud which would blot out the sun for a period of time, much like any massive meteor might. The best part of this is that, unlike a nuclear bomb, the land is ready for re-use immediately after the dust settles.


I am not sure what exactly you mean by "replace" but nuclear weapons have a very different role from other kinds of weapons.

Many strategists argue that nuclear strategy differs from other forms of military strategy. The immense and terrifying power of the weapons makes their use, in seeking victory in a traditional military sense, impossible.

Nuclear weapons have their role to play under MAD (Mutual assured destruction). Under MAD, each side has enough nuclear weaponry to destroy the other side. The payoff of the MAD doctrine was and still is expected to be a tense but stable global peace.

In order to fulfil the MAD role, the weapon must be capable of:

  • total assured annihilation of the enemy
  • have second-strike capabilities

So that leaves out all other kinds of weapons that were invented. While many of these weapons are terrible, they are still not capable of total destruction of the enemy.

Thinking about the future, two technologies that will change war forever are AGI and better batteries. The only thing that prevents a country from building an army of T-800 like soldier nowadays is software and better battery density. I would argue that a small army of these machines, all loaded with the perfect soldier AI could conquer a country quite easily.

  • $\begingroup$ When (if) they come they won't be even vaguely like T-800s, much more likely to be something like current commercially available drones with a gun of some sort mounted to be honest .. 🤔 .. or smaller, essentially self propelling explosive bullets, mini drones that loiter or hunt and seek targets .. either type could sit around in power save mode charging with solar cells with just the sensors working to trigger them if anyone passes by so those battery advances might not be as important as you think 🤗 $\endgroup$
    – Pelinore
    Jul 7 at 0:50
  • $\begingroup$ @Pelinore I disagree. I believe that they will come in several shapes and forms. Flying drones will definitely play a role, but they alone are not enough to win a war. You need land units. I can see dog-like robots (like Spot) being used along with bipedal human-shaped robots. The main advantage of being human-shaped is flexibility. They can tap into the existing weapon industry: they can drive vehicles, operate existing weapons without having to change the whole industry for them (e.g.: fire an AK47 or something like a Javelin), clear buildings, etc. $\endgroup$ Jul 7 at 8:40

The Sun Gun

The Germans had at least began the planning phase of this during WWII. The basic idea is placing a very large concave mirror in space (though many smaller mirrors is more feasible). According to their calculations, a 9 square kilometer mirror surface could reflect enough light to burn a city. While the initial costs might be steep, it would be reusable and cheap to operate.


This is a really good question

Before nukes humanity was experimenting with all kinds of toxic gasses, and various dispersible methods of destruction.

  • Mustard gas is a famous one.
  • Cluster explosives was another: Fragmentation Grenades born from this idea.

But genetic weapons would probably win.

- its possible to use retroviruses to trigger on specific biology.

Coded to the majority population of a region. (scary stuff)

That would probably be the most effective nuclear equivalence.

  • However genetics didnt really start until 1944... so theres many hypotheticals needed, first requiring that we did not start nuclear physics in the 1910s.
  • $\begingroup$ I think it'd (fortunately) still be very, very difficult to target viruses to a specific population - the problems are that there's a lot more variation in humans than we expect, and a lot more population transfer - you don't want to build a bioweapon to find it accidentally wipes out half your population that carry the gene variant you are targeting. Very genetically homogeneous populations might be less vulnerable to this, however - you'd have an interesting dynamic where the countries that could best use this would be uniquely vulnerable to it. $\endgroup$
    – lupe
    Jul 7 at 10:41

Just wanted to comment that the project Blue Dev is talking about above is the Rods from God program, and it was my first thought when I saw this question. Also, it's never really off the table and could still become a weapon due to its simplicity, but its cost has proved prohibitive due to the Tungsten rods costing about 230 million bucks a pop:

The “rods from God” idea was a bundle of telephone-pole sized (20 feet long, one >foot in diameter) tungsten rods, dropped from orbit, reaching a speed of up to ten >times the speed of sound. A concept design of Project Thor. -We are the Mighty has a great write up about it here

Basically, you're looking at a weapon that can bunker bust by plummeting deep into the earths crust and it would have an equivalent force to a conventional nuclear bomb.

Today, there is still another threat other than nukes that keeps big players honest in the form of biological weapons. Unleashing a terrible disease might not be prohibited if nukes weren't already a thing. Nations might overlook the awfulness in favor of its strategic value in such a situation.


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