You see it in movies: an invading entity is unstoppable with conventional weaponry and a desperate leader is forced (after much soul-searching) to detonate a nuke against said invader as a last ditch effort.

So my question is this: given the sudden appearance of a large alien creature (along the lines of a kiaju/Godzilla/Cloverfield kind of thing) plus a host of smaller accompanying creatures that are all extremely resistant to conventional weapons and going on a massively destructive rampage across the Swiss border and into France, what would the weaponry escalation path look like and at what point would the French President finally resort to the deployment of a nuclear weapon?

Or is this the kind of thing that would never actually happen?

I hope that is a clear enough question...

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Nov 3 '17 at 21:37

There are a lot of alternatives to nuclear weapons which are not explored in movies because the choice would be rather anticlimactic. Remember that these movies rarely make any sense; it's all about shock and awe, not logic.

Consider that a flesh and blood creature is going to be severely damaged by an explosion in real life, unlike movie monsters which are conveniently immune to armor piercing tank shells, napalm, etc.

First things first, this giant creature would be targeted by air strikes, and maybe face ground armor capable of delivering punishing ordinance. Have you ever watched a movie and heard the main character yell into a radio:

"Coordinates X, Y, Z, this is danger close!!!"

That's because the shock wave of an explosion (or the resulting shock wave from the impact of a kinetic projectile) can kill a human being. It's called hydrostatic shock. You never see Godzilla worrying about that in the movies, but in the real world that's something we're quite mindful of.

Also keep in mind that we are experimenting with Gauss cannons which fire square blocks of metal because aerodynamic ammunition would actually go too far. You know it kicks ass when that becomes a concern. And while there's severe limitations to the technology today, that will likely not be the case in 10 years, and I'm sure some exceptions could be made for an emergency situations. Anyway, moving on.

If for some reason regular ordnance proved to be insufficient (perhaps because there are a lot of parasitic monsters following the kaiju, which would difficult to wipe out in street to street fighting), there exist air fuel bombs, and other truly scary weapons which can deployed, and which are capable of wiping entire towns off the map while not being nuclear.

Only if these things failed would nuclear weapons even become an option, and most likely because there's a concern about some sort of contamination which might be killed off by the radiation fallout. To my mind, that would actually be the best reason to deploy nukes in the first place.

Imagine a giant monster rampaging through the streets of a metropolis. Sure, the monster is dangerous, but it's blood may be toxic, and there may be parasites which stream off of it, and which are actually a bigger threat than the Kaiju itself (think Cloverfield).

A nuke would solve that problem nicely. Kills the monster, and irradiates the heck out of any biological material left behind, killing any bacteria or viruses. Of course the collateral damage may be quite high, but it all comes down to a cost-benefit analysis. DO you risk these things getting out of the city and having to hunt them down for the next decade, or do you turn New York to cinders? And of course it's always New York.

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    $\begingroup$ Fuel-air explosives are some of my favorite things to read up. So very very scary. $\endgroup$ – Green Nov 2 '17 at 19:17
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    $\begingroup$ Do you have a citation for the aerodynamic projectices going too far? I'd love to read up more on that. $\endgroup$ – Green Nov 2 '17 at 19:26
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    $\begingroup$ Also a citation for the Gauss cannons please. $\endgroup$ – Leezard Nov 3 '17 at 1:29
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    $\begingroup$ What AndreiROM means with "too far", I think, is related to the tests itself. The Railgun (Gauss cannon) developed by BAE Systems, will be mouted for field-tests in the near future, it's far from being only an experiment. During tests, which BTW were made using only a fraction of the actual power of the cannon, projectiles with very bad aerodynamic properties were used to prevent the projectile from going too far in the test environment. $\endgroup$ – r41n Nov 3 '17 at 14:05
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    $\begingroup$ @r41n - Congratulations on being able to use Google! I'm not being facetious, btw. It amuses me when people ask for "references", when they could very easily just type "Gauss Cannon" into a search engine and read the numerous articles on the subject. Gauss cannons seem like they will really be a game changer, at least on platforms large enough to be able to power and use them (nuclear Navy ships are projected to mount them within the next decade, and I think a whole new series of destroyers are being built with them in mind). I mean .. what armor could withstand that sort of kinetic forces? $\endgroup$ – AndreiROM Nov 3 '17 at 14:14

The weaponry escalation would be local civilian weaponry such as shot guns, followed within minutes by police weaponry including machine guns. There would probably then be a pause. The situation would then rapidly escalate up the chain of command in the police force and at some senior level escalate into the political arena via some emergency procedure being triggered.

The Government leadership would be briefed on the situation within hours and further emergency procedures in place for terrorist attack would enable the armed forces to be activated. Depending on the exact situation on the ground and the proximity of the nearest available ground forces, the air force would probably be used next attacking with missiles and bombs within hours or possibly the following day depending on the time of day when the alert was first raised.

By the following day ground forces should start to arrive in quantity and engage the enemy together with attack helicopters and a lot more fixed wing aircraft from bases all across France. Given the French view on defence and the suddenness of the attack I doubt that any foreign forces would be asked or allowed to be involved.

After a few days a significant build-up of conventional forces would be available in the locality, including large numbers of infantry with conventional weapons such as rocket propelled grenades, machine guns and mortars. This would be supplemented by armoured forces and ground launched surface to surface missiles to engage the enemy in strength.

If these forces were defeated then I imagine the French president would be forced to use nuclear weapons. The first nuclear weapons used would be tactical (if the French have these). If these were unavailable or ineffective then larger nuclear warheads would be used.

It is impossible to say what the time span would be. It would depend on the exact location of the enemy, their numbers, the damage they had caused, the size of the area damaged, the speed of the damage, the number of people in the immediate vicinity, the effectiveness (if any) of conventional forces and other factors. I imagine it would come to a head quickly maybe a week or two, perhaps less.

  • $\begingroup$ Good answer, but I believe you are missing the inevitable air strike stage, where a large number of anti-armor missiles and bombs would get into the mix. $\endgroup$ – Twelfth Nov 2 '17 at 22:05
  • $\begingroup$ @Twelfth I thought I had? I suggested the French air force would attack within hours or at most by the following day with missiles and bombs. Followed up later the next day by attack helicopters and a lot more fixed wing aircraft from bases all across France. No doubt armour piecing bombs and all manner of munitions would be tried. $\endgroup$ – Slarty Nov 2 '17 at 23:43
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    $\begingroup$ Something tells me that the USA will engage as soon as it becomes obvious that France is incapable of containing the invasion. Considering how aggressive the USA is in modern times, they will simply disregard French officials and jump on the 'leaders of the free world and saviours of humanity' horse. Depending on a president, it can be the USA who decide to nuke the monsters. And then there is also Russia with its nuke arsenal partially targeted on Europe. If they feel sufficiently threatened they might also use nukes. $\endgroup$ – Olga Nov 3 '17 at 4:34
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    $\begingroup$ @Olga Traditionally, the US waits three or four years after France gets invaded. *cough* $\endgroup$ – David Richerby Nov 3 '17 at 11:25
  • $\begingroup$ @DavidRicherby, that's an old story... let's not talk about it. We greatly improved since then. Nowadays we do not even need to justify our military presence anywhere. And we found how to deal with the Congress. BTW, it was there fault we were slightly delayed before... $\endgroup$ – Olga Nov 3 '17 at 12:00

I think the first logical question would be "are they even affected by extreme heat and radiation"

After that, detonating a nuke over ones own soil is a rather personal choice. Detonating a nuke over another soil would be a very difficult choice because its virtually an act of aggression.

Would they do it? sure but they would have to know its effective and that there is no other alternative and that the enemy spread is uncontrollable.

As for progression. They would likely try chemical weapons before nukes. MOABs would be a good determiner of whether or not a nuke is even viable.


A nuke would be deployed when the cost of life of not deploying it far outweighs the cost of deploying it.

Large monsters aren't really a problem because there are so many non nuclear weapons that could be deployed long before having to resort to the nuclear option. Monsters would have to be extreme to warrant nukes. The threat really needs to be to the global scale of wiping out all human life or at least a good sized chunk of it to warrant it.

A disease is the most likely thing to get nuked. Anything like the zombie virus from Resident Evil or World War Z would be nuked at the first sign to burn out the infection.



Plans/protocols for usage of nuclear weapons on home-soil against invading forces already exist!

The geological features and proximity to/density of civilian population determines if a nuclear weapon can be used... and what size.

Two examples:

  • Sparsely populated mountain region can use a rather sizable yield weapon.
  • Paris is a "no nukes allowed" area.

To me, this means that the escalation to nuclear weapons could be extremely fast if the kaiju is coming from mountainous regions and conventional weapons (JDAMs, MOABs) prove useless.

Additionally, I feel that if the kaiju is known to be aggressive and is moving fast through the mountains, escalation to nuclear weapons could be near instantaneous; The plans to use them in this type of scenario are in place.

(I did my English 102 report on nuclear weapons 20+ years ago. Primary reference was a 1970's US House/Senate report.)

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    $\begingroup$ Welcome to Worldbuilding, MichaelKutz, your answer deals with the use nuclear weapons on American soil. The kaiju in this question is advancing into France after crossing the Swiss border. It is conceivable the Americans might use their nukes on the creature & in France too. Because I' m grouchy the freewheeling use of acronyms may sound cool and knowledgeable but it's pain to have to look them up. Your answer can be improved with more detail about home-soil nuclear doctrine. Thanks. And have fun here! $\endgroup$ – a4android Nov 3 '17 at 1:38
  • $\begingroup$ You wouldn't happen to have a name with that report, do you? $\endgroup$ – Mast Nov 3 '17 at 10:24

I'm running the risk of adding not an answer (as real life rarely considers kaijus) but I would like to add some real world info in addition to Michael Kutz's answer.

In the wonderful/scary (take your pick) book 'Nuclear Nightmares', Calder investigates the disposition of nuclear forces during the early half of the Cold War. The part that springs to mind is the section where he talks to US nuclear technicians deployed to Germany with 'tactical' weapons, designed to counter the wave of Soviet ground forces imagined in a possible invasion of Europe.

The parts that stick in my mind are that he defines the difference between a 'tactical' and 'strategic' nuclear weapon as;

Whether it is intended to be detonated in Germany or elsewhere

and that the US nuclear techs were complaining that;

The German villages were at most '2kt apart'

meaning that 2kt was the largest yield they could safely use without large damage to the local civilian populations.

So to attempt to answer the question directly, there is a long precedent of nuclear weapons being part of the generalist arsenal available to field commanders in Europe, to be used on home soil. In the specific example of a kaiju I would expect the use of the smallest yield weapons possible, to be used in areas of sparse population.

Nuclear Nightmares: ISBN 0563177403


Nobody has mentioned using a neutron bomb, which I think is the answer here. It sounds like France doesn't have any, but they could borrow some from another country or modify existing nukes. If damage, heat, and concussion from conventional weapons isn't working the next level is radiation. A neutron bomb is designed to give off as much radiation as possible at the expense of the blast radius. The US developed them to be used over friendly territory to stop the advance of Soviet troops without destroying the infrastructure like roads and buildings, but after human rights protests Europe didn't want anything to do with neutron bombs so they may not have access to them with short notice in real life.


The resonable escalation path would include two stops that haven't been mentioned yet:

Fuel-air explosives

A fuel-air explosive is a large conventional weapon that is basically just a lot of fuel. As it doesn't carry its own oxidizer, it uses oxygen from the air. This means the plane doesn't need to carry the weight of the oxidizer, and there's a lot of fuel that will turn a lot of oxygen into a lot of flames.

Your large creature can't rely carry a nuclear reactor (no cooling circuit) so it must breathe - and after being on the receiving end of a fuel-air bomb, it will be breathing in fire. This tends to be rather fatal.

Bunker busters

Modern bunker buster bombs are designed to penetrate into armor and explode on the inside. This can be quite damaging as the sort of armor that keeps shockwaves out is also quite good at keeping them in. There might not be a lot of visible damage on the outside, but the inside of the target will be turned into a fine puree.

Note that the latter weapon would initially be armed with a conventional warhead, but the escalation path would be to use a nuclear bunker buster. Having the nuclear weapon go off on the inside means that even a very small weapon (<1kt) would turn the thing into small chunks of radioactive meat. Sounds bad, but it does restrict the fallout.

  • $\begingroup$ Nuclear bunker buster... ouch!! $\endgroup$ – ZanderXL Nov 4 '17 at 0:07

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