If you've watched Godzilla and Pacific Rim you know what a Kaijuu is.

Kaijuus are monsters of epic proportions, as tall as the Empire State building or as large as 3 supercarriers of the USA.

I'm currently writing a short story about why monsters from "Another Dimension" keep attacking Earth.

Currently I have these reasons:

  • Prevention - Some super advanced alien species deemed humans way too destructive and periodically sends their monsters to cull the human population.
  • A viable world to live in - Kaijuus are living organisms as well, they have deemed Earth as a good place to stay and see humans as pests.
  • Conflict - Some hub dub story of a god siring 2 species, one of them are the Kaijuus who inherited the power, and the other are the humans who inherited the wisdom of the said god. Ever since, they are at war.
  • Emotional Negativity - They are attracted to the emotions of humans, particularly negative emotions.

As you can see it's rather short and I think the above reasons are rather superficial or not sufficient enough for Kaijuus to try annihilate the human race.

Are there any other probable reasons why a Kaijuu would attack humans?

Or are the reasons above sufficient enough to explain why Kaijuus are killing humans?

  • $\begingroup$ Not the war one. If we were warring with these creatures they would have destroyed us in the Stone Age. Same with the wanting to take over Earth. $\endgroup$ – Bellerophon Aug 27 '16 at 8:59
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    $\begingroup$ Whatever the excuses might be mankind will always be perceived as a disease or an infection so how do we take care of pest again... $\endgroup$ – user6760 Aug 27 '16 at 9:13
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    $\begingroup$ "Prevention" -- really, Kaijus seem like a rather inefficient (and possibly even counterproductive) approach. They only seem to kill a few thousand or tens of thousands of people, in very limited areas, and would probably provoke humans into being more destructive ("We need better weapons to defend against these monsters!"). $\endgroup$ – Peter Erwin Aug 27 '16 at 15:09
  • $\begingroup$ My kaijuu's kills millions a day and immune to nuclear ordinance $\endgroup$ – mico villena Aug 27 '16 at 15:24
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    $\begingroup$ Maybe they are angry or hungry? Or both? I think you need to look at why real animals, like dogs or the big cats attack humans. If they were a thousand times bigger, they would kill thousands. $\endgroup$ – n00dles Aug 27 '16 at 16:01

21 Answers 21


They don't need one. Let's say you take a walk. You're killing millions of microorganisms every time you breathe. You might step on ants and hardly notice. Crunch a snail when you aren't looking.

Essentially, they aren't hostile. They just don't notice the little creatures scrambling around, running away. They're annoyed these little stone things are in the way.

They're in essence a walking force of nature and they don't need to intentionally want to hurt us​‌​‌.

  • $\begingroup$ This kinda makes sense. Then if the question is why do they attack instead of 'accidentally' killing people, the answer could be that they are provoked. They don't intentionally want to hurt us, but because we freak out and attack them, they try to defend themselves. Then they realize some hostile species is attacking them from this planet, so they send more of their kind to wipe us out, like how we'd send people to kill animals if they were attacking people on the streets. $\endgroup$ – ASH-Aisyah Aug 27 '16 at 15:45
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    $\begingroup$ or they just wake up, wander out looking for coffee or whatever kaiju drink in the morning and oops. I consider the best monster movies ones where they're a natural disaster, rather than having 'motivation' - a typhoon or earthquake dosen't really care where they strike, its just the conditions. I think intent isn't necessary at all. $\endgroup$ – Journeyman Geek Aug 27 '16 at 15:50
  • $\begingroup$ I think intelligence is a big factor in the OP. $\endgroup$ – n00dles Aug 27 '16 at 16:04
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    $\begingroup$ This is, more or less, one of the themes in Roadside Picnic. $\endgroup$ – Martin Tournoij Aug 27 '16 at 16:24
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    $\begingroup$ So we hoomans are basically some kind of very annoying, excesively territorial wasp. You normally don't actively exterminate wasps. You just avoid scaring or pissing them off. But if they would get actively agressive, to the point where they start going after people and actually killing them... well, then the fumigating starts. $\endgroup$ – xDaizu Aug 29 '16 at 8:29

Don't Rule Out Politics

Just because the Kaijuu and intergalactic beast monsters doesn't mean that they aren't intelligent, or exists in complex societies with unforeseen political pressures. Maybe the Kaijuu are attacking Earth because some Kaijuu monster politician with a bad toupee who ran on a "Humans are Evil" populist platform just was elected President.

  • $\begingroup$ Omg I see what you did there. Vote up. So next year, should we be worried that some Earth-born Kaijuu would really rampage all around the world? I guess then, unlike in the movies, America would be the only safe place... $\endgroup$ – ASH-Aisyah Aug 27 '16 at 15:49

Kaiju are aggressively active critics of bad architecture. See it, don't like it, then knock it over. Note that creatures the size of the Empire State Building like Godzilla preferentially attack cities, power stations, and high-tension power lines. Either knocking them down or melting them with their radioactive, thermonuclear bad breath.

Humans aren't their true target. They just get in the way of demolishing cities and get crushed when the building come down or burned up or plain old-fashioned stepped on. Humans shouldn't take it personally.

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    $\begingroup$ "I just woke up this morning and hated everything..." $\endgroup$ – Scott Downey Aug 27 '16 at 13:57
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    $\begingroup$ @ScottDowney Just find a city to demolish. You know you'll feel better afterwards. $\endgroup$ – a4android Aug 27 '16 at 14:11
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    $\begingroup$ I totally would not shed tears if a rampaging giant atomic lizard destroyed that building that's blocking my view... ;p $\endgroup$ – Journeyman Geek Aug 28 '16 at 16:08
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    $\begingroup$ I totally like this. Let's leave only Douglas Cardinal's building standing up. $\endgroup$ – Félix Gagnon-Grenier Aug 28 '16 at 23:12
  • $\begingroup$ Makes me think of The Far Side cartoon. $\endgroup$ – JDługosz Mar 20 '17 at 6:28

Petty revenge and escalation.

It's pretty easy when you consider humans as the equivalent of insects to the kaiju. There is no need to model the kaiju as a force of nature, they can be completely intelligent and human-like, yet their desires would be completely inscrutable

Imagine a group of 6-year old schoolboys playing in the park, when they stumble upon a hornet nest. Being schoolboys, they poke the hornet nest and therefore get stung by the hornets. They then run away, crying to their friends about the hornets.

The next day, they bring the baddest boy of the school to try to destroy the nest. He brings along a lighter and a bottle of insecticide and tries to flamethrower the nest. Unfortunately, he only destroys part of the nest and is once again driven away by the hornets' stings.

The story usually ends in two ways: The exterminators are called in and the hornet nest is professionally destroyed, or the parents tell the children to stop poking the hornets' nest.

Now, imagine the story from the point of view of the hornets:

Day 1: A number of 100m-tall kaiju rampage through their city, destroying a few city blocks and killing hundreds of helpless children in their nurseries. A swift decisive defense is mounted and the 100m-tall kaiju is driven away with significant friendly losses.

Day 2: A 200m-tall kaiju approaches, breathing fire and leaving terrible infernos in its wake. All who try to stand up to its flames are completely annihilated. It incinerates the better part of a suburb. A massive defence is organised, involving 50% of the population fighting for their lives and their home. They finally manage to repel the kaiju, but 30% of the population of the city lay dead at the hands of the kaiju.

Day 3 (a): The kaiju mothership arrives, wreathed in an impenetrable white forceshield impervious to all known weapons. It exudes neurotoxins and smog, instantly killing everyone who as much as touches it. The entire city is destroyed. The kaiju mothership then summons a moon-sized spaceship which rips the city right off the land and engulfs the obliterated remains of the city.

Day 3 (b): The kajiu threat was repelled, and the citizens start their arduous journey of rebuilding. Even though a few kaiju are sometimes sighted by scouts, they never think of threatening the city ever again.


Other reasons might include:

  • Food:

Kaijus are carnivorous creatures and humans, being abundantly available in all places, are naturally their first pick for an easy meal.

  • Rare elements:

That is somewhat relevant to the first point, but not the same. Kaijus have some rare elements in their bodies, which are hard to come by, on Earth, but are found in relevant abundance (few hundred parts per million versus few parts per million in the soil) in the human body. Kaijus kill and consume humans to replenish their rare elements' requirements.

  • Humans started the conflict first:

This is all too common a cliche. Like the belligerent, egotistic, messing race we are, we discovered some Kaijus in some far off region and immediately considered them a threat, taking them down with fighter jets and tanks. This initiated a violent response from the previously docile giants and now they are rampaging all over the globe.

  • Indirect carnage

The Kaijus don't directly involve in killing humans (as in, they don't step on, or swat at those pesky little worms) but the way they interact with their environment ends up killing swathes of humans. Consider a Kaiju kicking off a man-made building out of its way because it is an obstruction to it. Although not intended, hundreds of humans would die as a result. Some crunched within the building and others die as huge blocks of debris fall on them.

In this case, the Kaijus are sensitive to a lot of pheromones that humans release. In most cases, these pheromones incite the Kaijus to violence. If human and Kaiju pheromones overlap in this manner, Kaijus would be hostile murdering machines only in places where there are large human populations (large cities) releasing huge amounts of pheromones, affecting Kaiju behavior in their vicinity. Kaijus present/living in or around small towns or villages would be docile and peaceful.

  • Natural hostility

This is what makes a cat kill rats. In the long course of evolution, certain species got to be perpetually hostile to other species (dogs-cheetahs, lions-hyenas etc). In this case, Kaijus were an ancient race which evolved alongside humans and both species developed animosity against each other. In those times, the Kaijus were about the size of elephants. However, for reasons unknown, Kaijus apparently disappeared from Earth dozens of thousands of years ago. Now that they are back and huge (how they are back, it's upon you), the ancient animosity has flared up again and they are on a kill spree.

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    $\begingroup$ that is strangely straight and i like lit $\endgroup$ – mico villena Aug 27 '16 at 9:34
  • $\begingroup$ Vote up just for that last point XD $\endgroup$ – ASH-Aisyah Aug 27 '16 at 15:47
  • $\begingroup$ Food is a poor reason to attack humans for. In comparison, the deer in the forests or the fish in the seas are far less likely to fight back than humans. Humans are also nutritionally not significantly different from most animals. $\endgroup$ – March Ho Aug 27 '16 at 16:11
  • $\begingroup$ (point 3) But there is no evidence of this. Points 1 and 2 could just be protien or sugars(energy etc). Like why we eat. +1 for "Food". $\endgroup$ – n00dles Aug 27 '16 at 16:12
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    $\begingroup$ @MarchHo yes, but they are far far too agile and hard to catch than slow, scaredly humans, who are also available in far greater numbers, too. $\endgroup$ – Youstay Igo Aug 27 '16 at 16:12

Entertainment: the whole scheme involves televised events, where the "super-advanced alien race" has design contests for new kaiju to be sent in against some randomly selected (or maybe voted upon) city, with bets placed on how long the kaiju lasts or much destruction takes place before the humans finally take them down, or what method the humans finally use to beat them. Sort of like gladiatorial games for the ancient Romans.

(Invulnerable kaiji would get boring after a while, which is why it's always possible for the humans to defeat them.)

(We find it entertaining to watch movies of giant monsters destroying cities, after all.)

  • $\begingroup$ Sounds like Hunger Games... $\endgroup$ – ASH-Aisyah Aug 27 '16 at 15:50
  • $\begingroup$ When I become a God that is exactly what I would do! $\endgroup$ – Nick Dzink Aug 4 '17 at 22:31

It's their Super Bowl.

The short and sweet of it is your aliens are not that mature or empathetic and watching two lesser species fight to the death is entertaining.


The Kaijuu are the spirits of the fire and power of early Earth. God wanted to put life on Earth so (s)he banished the Kaijuu to another dimension in order to make Earth suitable for other life. After millions of years the Kaijuu have cracked the wall between dimensions and are coming through. They see life on Earth as their replacements so they try to destroy it and return Earth to its primal state.


With a range of tones:

  • "I would like to say that the humans worship [deity], the same way we do. I'd like to, but ... they're doing it wrong. And, as we all know, the only compassionate choice is to kill them all."
  • "Professor, we have finally determined why all of our interpreters become psychotic. It seems those little human insects's brains broadcast thoughts so violent and depraved that our psychic colleagues lose their minds."
  • "The brains are just so damned tasty!"
  • "Once we've eliminated the vermin overrunning the planet, which, get this, they call "Earth", a synonym for dirt, we'll be able to retrieve the buried creche without infecting our young.
  • "And, as we can clearly see in our telescopes, there are no creatures sufficiently large to be 'life'. Therefore, this wet, blue planet will be a perfect remote home for our criminally insane."
  • "We used to call it "the common cold". Now we call it Mad Kaijuu Disease: 'MKD', also expanded as 'massive killing and destruction' in the popular lexicon."
  • "It's taken us a century of painstaking science, and the death's of several hundred indigenous species, but we have finally determined that it was the rays of the yellow sun that were causing our first settlers' violent mood disorders."
  • "Thou shalt not abide the tailless to live."
  • "While mild mannered at the somewhat lower[higher] atmospheric pressure of our own habitats. When we sent Steve down[up] into that much thicker[thinner] atmosphere, we discovered he is susceptible to nitrogen narcosis at those pressures. We'll miss Steve, and the millions of recently discovered local inhabitants he inadvertently stepped on and stumbled over."
  • "We seek to capture and reimprison our most accomplished identity thief, most likely disguised as one of these rectangular pebble sculptures."
  • "Aw, Mom, if we'd thought they were sentient, we wouldn't have knocked their hives over."
  • "That, Timmy, is why we do not let our pets off their leashes outside of our home."
  • "They said I was mad to develop this germ line of microcephalics. But we'll see who says I'm mad, now that I've worked out the kinks via direct conflict testing on this backwater planet."
  • "They told us this portal would just disintegrate our criminally insane. We would never have used it if we had known it went somewhere."
  • "We have seen this 'Jersey Shore' and our wisest minds are in agreement: You must be destroyed."
  • "We have seen this 'Lost' and our wisest minds are in agreement: You must satisfyingly wrap up all the loose ends. Or else."
  • "Of course I'm allowed to stomp all over this city. I have my letter of marque right here."
  • "The license says I'm allowed to kill up to 8 million, when they're in season."
  • "It's my homestead and the law says I can clear varmints from my land any way I see fit."

Similar to your prevention reasoning, for harvesting natural resources. An advanced alien species sends the Kaijuu to destroy local planetary inhabitants before they arrive to farm the planet's natural resources.

  • $\begingroup$ fairly straight forward and efficient. why kaijuu not them selves? $\endgroup$ – mico villena Aug 27 '16 at 13:15
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    $\begingroup$ Perhaps they send the Kaijuu becuase their species has evolved beyond the need for physical strength. For example, as their species evolved and lived in a highly advanced society, their physical bodies became weaker and frailer, as physical strength was no longer necessary and intellectual strength was valued. They outsourced all their physical labor to technology, so their species evolved accordingly. So they send the kaijuu which they control, to exterminate local inhabitants and secure the planet before their machines and scouts arrive. $\endgroup$ – Dani Aug 27 '16 at 13:26

They do it for the bonus points, of course.

enter image description here

But seriously, what if they are simply very large bio-machines designed to collect resources of some kind (organic, genetic, mineral... whatever) and they are competing with each other?

If whatever source they came from has a competitive, entertainment based society, there may even be masses of beings gathered into massive arenas where giant holograms are reproducing the perceptions of the senses of the bio-mecha-kaiju stomping around the next dimension over.

There could be legions of fans rooting for their favorite monster and smack-talking the others, commentators excitedly covering every move by the kaiju and the prey - maybe even multiple commentators each streaming their own channel so the spectators can pick their favorite voice, popcorn and hotdogs and sugar-spiked drinks... or whatever it is they drink and eat over there. Perhaps they view humans much like we view ants, capable of great feats of engineering, but not really intelligent.

Besides, there has to be some reason why they keep attacking Tokyo. I'll bet you there's an alien poke-stop there or something.


Thinking of this as more of an invasion from another dimension, this could be a

prelude to an invasion

This Kaijuu attacking a city could be an initial attack on humans to test specific weakness in our defenses before the actual invasion by a hostile alien race.

I can think of three situations of how they would achieve this:

1. A Soldier

The Kaijuu is a soldier of the 'alien race'. He is of the same race as the alien race, and during this initial attack, he is to show no ability to reason.

2. A Soldier's "Dog"

The Kaijuu is of a different species to the alien race. It has less intelligence and a very different appearance to the alien race. It is used for it's voraciousness and high tolerance to weapons. And furthermore it is mentally prepared for the attack by the alien race.

3. A Synthetic or Bio-Mechanical Creature

The Kaijuu was created by the alien race specifically for this task. It is made to shock and overwhelm the humans on a small scale. It's appearance is designed to look like it had been living in Earth's sea. This creature gathers the information needed for the main invasion assault.


Godzilla is the best example imho. You could adjust the motivation to meet your scenario.

Every time an act of evil happens in our world, a pocket of negative energy travels through to our shadow world or Kaiju dimension. Eventually enough energy collects and a Kaiju is born. This energy backfires through the tunnel and the Kaiju travels back to our world. The process is extremely painful and form-changing for the infant Kaiju. As it enters our world, the very first thing it experiences is pain, darkness and loneliness. Inherently evil, immensely powerful and angry from the start. What happens next would seem natural.

This scenario takes away from Kaiju being a physical monster a bit and the logistics should be more detailed

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    $\begingroup$ Wow, I never thought I would hear a New Age theory of Godzilla. $\endgroup$ – Doug Warren Aug 29 '16 at 13:19

Maybe they do it for fun?

Any child with a magnifying glass and a hot summer day has had the same experience: burn the ants. It's fun. Yes, it's cruel, and yes, most adults wouldn't let themselves be seen doing something so detestable for a person well past puberty, but perhaps the Kaijuu have different reasons:

Cultural stagnation

Godzilla meets The Hunger Games: Kaijuu compete with each other to cause the most mayhem on Earth to prove the superiority of their home districts to distract them from the insidious undercurrents of their society.

Boys will be Boys

Kaijuu have immense power to traverse space-time and so the billions and billions of star systems are their playthings. Most adults prefer to vent their stress in abandoned systems or asteroid belts, but angsty adolescents sneak into the star systems of intelligent life and cause a wreak because they won't admit it but they want their parents to pay attention to them more, especially after their Kaijuu parents split up and brought in Kaijuu step-siblings in their second marriages.

Gentlemanly Hunting

In, say, Middle Ages-era Europe, it was common for the nobility and their associates to spend their leisure time with their associates by hunting. It was seen as a gentleman's sport. Perhaps the Kaijuu venture forth with monocles the size of the Hubble Space Telescope.


Global Warming!

Or some other natural/man-made change in the creature's natural environment affects the creatures primary food source.

This may force the creature to leave it's natural environment to seek a more abundant source of nutrition.

A human gathering(i.e. a city) could be discovered through eating fisherman, and following the trail intently or not, to the dock of a city. Hungry and malnourished, the creature is confused and looking for sustenance. (Cue the blonde woman looking up and screaming). Seeing modern technology like cars and neon lights could make him more hostile, confused and angry.


The scenario I like is they attack because they just like violence. Not every vile and ferocious creature has to be sugar-coated in a movie for us, so we can understand their motives and why are they doing this. Think of the situation as a desperate one, there are creatures that like rampages, killings, blood and carnage.


Depends on the reason these gargantua showed up in the first place, but let's say YOU just found a cool new planet to live on, with lots of good breathable air, plenty of water, vegetation, etc., which was a super handy discovery since you were previously planet-less. So you land, all excited to get your new life started, and you discover there are teensy little critters infesting the place, covering it with their weird little structures and whatnot -- well that's all fine and interesting, you'd be happy enough to live and let live. Only, unlike roaches and ants and spiders and other such teensy critters which you've found a mild irritation in the past, these seem to be intelligent and rather annoyed and terrified by your arrival, so they start trying to, you know, kill you and stuff. And it turns out, they're actually pretty dang smart and unusually effective at making things dead.

Plus, they're everywhere, so (as has been mentioned in other posts), you can't really help but keep stepping on them, which they seem to not like very much.

So yeah -- intelligent, terrified, nuke-wielding ants with itchy trigger fingers, and you with no place else to go.

What would you do?

  • $\begingroup$ I'd check if this planet has some comfy place with less ants (or at least less bitey ones). Kaijuu, on the other hand, seem to be attracted to megacities. $\endgroup$ – user8808 Sep 7 '16 at 13:23
  • $\begingroup$ Fair enough.. Although, bear in mind that these particular ants are also (a) notoriously curious, being simultaneously fascinated, terrified, and enraged by anything new or which they don't yet fully understand (which is most things); and (b) envious of anyone who seems to have anything which they particularly notice they haven't got, especially if that thing is big comfy places with less ants than where they already live now. I'm just saying, maybe in these Kaijuu's experience, it's mostly better to just go stomp on the biggest anthill right from the get-go and have done with it. $\endgroup$ – Brian Lacy Sep 8 '16 at 6:48

Imagine the "weird" pleasure we humans (or most of us, at least) feel when we kick/step on/destroy a sandcastle, and multiply it tenfold. Maybe they have no real motives or reasons to destroy cities apart from the fact that it might be fun as hell, or at least relaxing, to them, coupled with the fact that we would be perceived by such a creature the same way we perceive ants.

Speaking of ants, another good comparison would be a very small kid who burns ants with a magnifying glass. He's not evil, he's not trying to make the anthill his new home and he's definitely not looking for food, he's just having fun. And if the monster is intelligent but not like a human adult (e.g. not self-conscious, or as much as a little kid can be) it could basically be the same thing.

As to why the Kaijuu decides to travel to our world, we first would have to know what their world actually is like. It may be barren and "boring" or they could even have come here by mistake or unconsciously.

In that case, attacking a city might even be a decision dictated by the "panic" caused by the fact of finding itself in an unknown world surrounded by unfamiliar things.


It's beyond our understanding:
I'd like to refer to Neil DeGrasse Tyson on this:

To summarise, he states that everything we are that's different from chimpanzees can only exist in the 1% difference of our DNA from chimps. So building computers and swinging from the trees is only 1% difference. Now imagine an alien race 1% smarter than us in the same way we're smarter than chimps, or suppose they're 2% smarter. Suppose these Kaijuu are somehow related to that alien race, we'd simply lack the intelligence to fully understand why.

The Galactic Prime Directive:
My other suggestion, we're being prepared. Our 20years of world wars advanced our technology faster than the previous 200years. To an alien race war would seem like a good motivator to hurry us along. Now all the world is working together to fight a common enemy. Perhaps we have some friends out there preparing humanity for the rigours of a galactic community by putting us through the galactic prime directive.
"Only races strong enough to survive and overcome the Kaijuu are strong enough to join the Galactic Council".
Kaaiju in this context may simply mean test. We're a war like species, so our test is war...


Maybe the Kaijuu is really just an enormous garden hoe?

In that case, we'd be like ants, and buildings would just be seen as weeds.


There's a word zoologists use, territoriality. It's a hell of a word when it's applied to something like a hippo, that will chase you down and stamp you to death for the crime of existing near it.

I imagine it would be a hell of a word when applied to a kaiju, which will roast your city for the temerity of being a few miles from its nest.


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