In the early 1950s an aquatic race called merfolk for simplicity sake was discovered. But they weren't friendly in order to scare them off the crew that discovered them fired off a warning shot which hit and destroyed a precious religious artifact of a large tribe by mistake. Before they made there escape while humanity is surprised they don't really do anything because they have nothing to trade or offer stuck in the Stone age because of no fire to make more advanced tools so while they keep an eye on them humanity does nothing over the course of several decades the merfolk unify under said large tribe and prepare an all out war against the "above demons". They start by launching an all-out invasion of the Philippines the federated Republic of Micronesia and Samoa killing up to 300,000 men women and children in 2009 before invading the countries along the Western Pacific Ocean. Now humanity is trying to figure out how to take the fight to them and either subjugate them or wipe them out they refuse to use nuclear weapons because of the risk of poisoning the ocean.

The merfolk live 10,000 meters under water are a lot stronger and tougher than humans due to sustaining such pressure and being fine they have sonar abilities to use like ranged weapons along with being highly venomous with the population ranging around 5-10 million merfolk they have tails like eels with a humanoid top and able to move on land based on how much water they absorb. how would humanity be able to fight against such an assault from the depths.

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    $\begingroup$ This seems to assert some things which make little sense and confuse the matter. Nuclear testing has occurred extensively underwater - the effects are known and fairly local, then there's the reason they don't die of gas un-dissolving from every tissue of their bodies and killing them when they surface - it's completely fine if you want to write those things into your story, but it leaves a whole lot that we don't understand about your world. It does render questions of how to fight them rather opinion-based as there's no way to define what constitutes a best answer from your question. Cont. $\endgroup$ Commented Oct 17, 2021 at 0:55
  • $\begingroup$ If you take our tour and have a read of our help center you'll get the hang of the sort of things we expect of a question: to be answerable, to be well enough defined to identifiably have a "best answer" etc. Then you can edit the question to fit a little better, and get a more definitive and helpful answer. $\endgroup$ Commented Oct 17, 2021 at 0:57
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    $\begingroup$ able to move on land based on how much water they absorb What does that mean ? They have tails, so how does absorbing water (which has weight) help their movement ? You really need to think that out because armies that cannot move effectively are not useful. How can they outpace a human which is evolved to move on land as a matter of survival ? $\endgroup$ Commented Oct 17, 2021 at 4:47
  • $\begingroup$ "they refuse to use nuclear weapons because of the risk of poisoning the ocean" I think you haven't researched the 1950s very well. They would totally nuke the Mariana trench without batting an eyelid. $\endgroup$ Commented Oct 17, 2021 at 19:39

3 Answers 3


Your merfolk are screwed. Even if they mounted an attack in the 1950's.

In the 1940's we went through the world wars. We built tanks, rockets and submarines. As soon humans get their war machine back into gear there is very little your merfolk can do.

Even in the initial attack, I suspect their casualty rate would be horrific.

  1. Humans are pretty tough creatures. Our prehistoric tribes hunted elephant, and lived toe-to-toe with snakes. Even back then we dominated. Just because a creature is faster, stronger, has larger teeth, or is more venemous doesn't mean humans will automatically lose.

  2. I'm a normal(?) citizen, and things that are immediately available in my garage that can be used offensively include:

    • A car. Let's go run over some merfolk! Have you ever tried to punch in a car window with your fists? a car is a pretty tough machine.
    • An axe. Let's fight the same way they fight!
    • A cordless angle grinder. I don't know what this would do to a merfolk, but it wouldn't be pretty. Many houses will also have chainsaws, or if you're an American, you've probably some sort of gun within shouting distance.

Given a few days I'm sure youtube contains instructions sufficient that I could cobble together weapons such as:

  • A Flamethrower
  • A Crossbow (or a triggered-slingshot)
  • ??? (I'm too scared to do a youtube search for "homemade weapon"). But consider that many "terrorist" groups improvise their own weapons.

After humanity get's their act together, the merfolk are doomed. What can a merfolk do to a submarine? Without explosives, even a non-military submarine is probably relatively invulnerable.

So here's the plan I would enact were I a military general:

  1. Find where the merfolk cities are. Scout around with the sub fleet till you locate them. I don't know the sonar capabilities of a modern warship, but there's a fair chance they can also scan down to fairly significant depths.
  2. Send a bomber to fly over and drop depth charges on all their population centres. Don't have depth charges that work at 10,000 meters depth? I give the Seabee's or some other combat engineers about a week to figure something out.

And with this, the humans can completely obliterate the merfolk at approximately zero risk to their armed forces.

  • $\begingroup$ 1950s and cordless angle grinders and YouTube are not compatible. So that's petrol fueled chain saw and public library for the 1950s. :-) $\endgroup$ Commented Oct 17, 2021 at 4:32
  • $\begingroup$ I was under the impression that although merfolk were discovered in the 1950s, they waited until present day to attack. I'm not too certain of that though. $\endgroup$
    – sdfgeoff
    Commented Oct 17, 2021 at 17:47

They can barely fight humans at all

The merfolk wouldn't be able to make much damage to begin with. Their superhuman attributes means Little again the firearms of that time. Lacking adaptations to walk on land, they would just drag themselves pathetically, their sonar would not work as a weapon in the air and it is unlikely they have ranged weapons since those are largely ineffective under water. Thus the moment they step in land, humans can slaughter them even while being grossly outnumbered.

On top of that, their lack of technology and organization (tribal) means that they cannot concentrate their forces to a meaningful extent as they can not provide the logistics to feed an army. Regardless any large scale attack would easily be repulsed by the military.

Even if they go for a guerrilla war, attacking coastal areas and then retreating to the sea, humans could easily protect any coast they really wanted, they just need radars to detect larger groups and arming the civilians so they will not be caught off guard against a small raid band.

They can be a little disruptive to sea trade

That's pretty much all they can do outside the suicidal inland invasion. There thay can hide effectively from humans in the depth of the sea. Make no mistake, humans still can trade in the sea, but now they do it in larger scouted fleets, the merfolk will only be able to threaten small and unprotected fleets and still the humans would likely win by just throwing bombs in the water.

Overall I think this tribal confederation would dismantle almost immediately and even the offended tribe would bail out as soon as the humans realize they are at war



Depth charges. Bah. Too easy. This movie will be over in 15 minutes. Plus no-one will cheer for blowing up the merperson hotties you introduce in the beginning.

I propose instead that the humans use chloroform.


Denser than water, the cold chloroform will shoot down through the water and form a layer on the bottom where the merfolk live. They will not even know what hit them. They will just get sleepy and doze off. Most of them will die but some are saved (including all merperson hotties) - trained elephant seals will dive down there and collect the sleeping merfolk and put them in aquatic zoos and people will come and laugh at the merfolk, or hate on them because of all the people they killed. Or both!

To be clear: the elephant seals are only involved in the retrieval part, not the zoos or the laughing or the hating which they don't know about and probably would not approve of if they did. If you don't like the elephant seal part of this answer you could substitute robot elephant seals.


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