Is this close enough to a squirrel for you?

If you presuppose them to be intelligent, and to have an active civilization, they they have to have something better for paws (and brains)

And if you allow that, just where do you draw the line?

For starters, you might want to take a look at what Shadiversity posted on YouTube regarding which kinds of weapons were most suitable for fairies: https://www.youtube.com/watch?v=iV-g88OMzcU

Basically, when thinking about what kinds of weapons a tiny sapient squirrel-like creature might want to employ in combat, you'll need to think about how the square-cube law (where every time you double a creature's size, you quadruple its surface area, and multiply its volume, and possibly mass, by 8x) would come into effect. Given how much stronger squirrels are for their size compared to humans, given how much higher they can jump, given how fast they can run, and given how real-life squirrels jumping onto you might make you jump (like in here: https://www.youtube.com/watch?v=4GIijT2U_8M), imagine how terrifying it would be if (like a thrown knife or shuriken) one were to leap straight onto you while brandishing a knife-sized spear in hand. (What they lack in their ability to put their weight behind their weapon strikes, they could make up for the velocity that they can employ for their weapons.)

P.S.: Fun fact: Thanks to the square-cubed law, small mammals like squirrels are more likely to survive falling from kilometres above sea level (assuming earth-like conditions of course) than humans are, simply because their greater surface-area-to-volume/mass ratio is so much higher, resulting in lower terminal velocity. Thus, whereas a human falling from the edge of space might require a fairly large parachute to survive landing, a squirrel might only need a cloak to hold onto (making it akin to a flying squirrel).

Preferably use a body armor with the tail, paws and head coated in offensive spikes. For setting things on fire, they would use something like these claws:

Edit: Today, I learned that squirrels are omnivorous: Squirrel chomping on a mouse (Video).

Given squirrels' masterful ability to overcome bird feeder defenses through their tremendous agility, dexterity, tenacity, and puzzle solving skills, I'd say you've got a good argument for rather Rube Goldbergish weapon systems. Given their proclivity for heights, I'd say that gravity fed projectiles and castle-defense measures mounted on Oak trees would be their MO. Also, if they have any amount of breathing room to cultivate things on this planet, they would be planting oak orchards and protecting the oldest, most productive trees and would build up multi-clan societies as tree to tree cities. They are already rather family and clan oriented and would quickly form larger scale mutually advantageous societies allowing them to share information across distances and circulate rare/specialty goods; this would allow for the development of more advanced weapons. As the rats of the trees, they're going to be hardy and fierce, however, I would expect their methods of war to be conservative and opportunistic since most rodents have strong predator-evasion instincts (hence the ranged weapons from on high).

And might I agree with my fellow thread poster... "rabid berserker squirrels". ... ohhellyeah

Two things not mentioned yet (especially useful when combined):

• Mass group attacks. This would require behavioral change only, and since they have become intelligent, that's just a decision to take. With their agility, claws and teeth you do not want to face 200 squirrels attacking you.

• Use sand, it's widely available and you don't have to carry or maintain it. That same number of animals thowing a barrage of sand in your eyes, nose and mouth is again something to avoid.

Nuclear weapons dropped from orbit.

If intelligent monkeys can manage it, why couldn't intelligent squirrels?

Has everyone forgotten the scariest weapon that small mammals wield IRL?

Biowarfare.

Granted squirrels rarely carry rabies, but woodchucks accounted for 86% of the 368 cases of rabies among rodents reported to CDC. It wouldn't be a stretch to have rabid berserker squirrels.

If the squirrel civilization has metallurgy -- or even basic stone knapping, if they can do it precisely enough on a small scale -- they could get Wolverine-style claw extensions. (See: Guardians of Ga'Hoole series, for owls.)

This option gets around the issues with having to hold something in mouth or claw, by simply extending claws. Note, however, that the claws would need to be very strong and well developed, or alternatively not interfere with the process of walking or climbing by attaching above the hooked section.

Arguably, this doesn't necessarily grant much of an advantage to the squirrel, since their claws are already so sharp. Might be decent for stopping predators, though.

Squirrels are notorious for gathering and busting/cracking nuts with their front teeth and jaws. I recommend when in danger, they just go for the nuts.

Having had a squirrel drop a slice of bread on me, it's pretty obvious...

They ambush and drop something heavy from high overhead. All you need is some good pine trees that produce large pine cones. The coulter pine (thanks to DJohnM in comments) would be a good candidate. They can weigh 10 kg. Now imagine that the squirrels are dropping these from 10 meters high. That's a 10 kg weight going 50 km/hr at impact. https://www.angio.net/personal/climb/speed.html

Give your world slightly larger pine cones or slightly larger trees, and no one survives a journey into the Squirrel Wood.

Two thoughts.

One, utilize dangerous animals. Enrage a boar into chasing you, then run through a group of humans. Encourage bees to move to strategic locations, then cut whatever is supporting their hive on top of invaders's heads. Train a bear to not think of squirrels as food, then live near its den. Have pet skunks. The world is full of creatures that can do far more damage than a squirrel can.

Two, guerilla warfare and crazy revenge. In a straight fight, a squirrel probably loses. But they'd be great at sneaking around, hearing secrets, lighting stuff on fire, slitting throats in the night. Having a culture where you let people know that you will wreck their shit if they mess with you is a pretty effective deterrent, even if the other side knows that they would win in a straight fight.

Just to add on - Squirrels have extremely sharp claws. The reason they're not considered good pets is that they'll cut through your flesh pretty easily just by innocently trying to climb up your leg.

Ask any veterinarian that's cared for a squirrel before releasing it back into the wild: They're cute, but their claws and teeth are extremely painful.

Traps, ropes, wires and poison needles; maybe in some kind of spike helmets.

I think that due to the size and structure of a squirrel it is best to let them move naturally in CQC.

Traps are static so they are kind of trivial as there is no need to specialize them for squirrels.

Poison needles can kill. With some kind of a helmets the squirrels can move naturally and swarm over armored enemies and get to weak spots. Traps can help to immobilize the enemy as do ropes and wires.

The squirrels can use ropes and wires in groups. Due to their low mass they could quickly make some kind of trap like mechanisms to utilize counterweights. Nothing more than some basic like a rope tied to a stone dropped over a branch.

Cutting wire will be pretty nasty against unarmored enemy, even without counterweight.

Having observed squirrels, and watching them move from tree to tree.
It seems obvious that they would prefere ranged weapons.
The only good reason to be on ground level is to find fallen food.

Nature provided them with high agility and excellent reflexes.
(just look up that youtube video of a squirrel stealing food from a cat, and you know how badass they can be).

Since they probably want to keep moving in the trees, it wouldn't be a weapon that they have to carry by paw.

So something they can carry on their back.

And not something overly heavy that would mess up their balance while jumping branches.

A possible solution for those requirements?

A pawheld catapult to shoot explosive acorns.

Of course, medieval armor and a nice spear would go a long way. We even have a name for these armed warriors: Spearrels.

Here is one such exemplar below:

Fierce indeed.

Interesting answer from Andreas, but I'd take issue with one of his points

Since squirrels are fast and agile, but rather weak

For their size, they are anything but weak. I mean an animal that can dart up a tree as fast as one can blink can hardly be said to be weak!

I was feeding a tame squirrel in Hyde Park (London), and having run out of nuts I held out my empty hand loosely clenched. This squirrel managed to haul open my fist, with one arm on my thumb and the other hooked round my index finger, with amazing strength (although I didn't put up much resistance). On finding my hand empty, it gave me a token nip, which I'm sure could have been much harder had it wished!

Getting to the point, I think a squirrel would likely make more use of its back legs. Perhaps it could fit a sharp scythe-like blade to each back ankle and thus be able to fight like a cockerel leaping up and slashing at its opponent, and likely holding a couple of shields in its front paws, to protect itself from a similarly armed opponent.

A squirrel could wield quite a large bow and arrow by rolling on its back and bracing the bow on its back legs and hauling back and releasing the bow string with its front arms. If it fired a poisoned arrow and then scampered off and kept out of the way until its prey succumbed, it could kill a sizeable animal.

Perhaps it could make good use of its large incisors by attaching round its head an armoured helmet with an artificial set of external teeth-like blades or spikes operated via a spring-loaded caliper arrangement by its real teeth inside, if that makes sense. Again, if the external blades were poisoned, it could bring down a larger opponent, although with this contraption close to its mouth and probably breathing heavily it would have to be careful not to ingest the poison!

Also, let's not forget its large tail. It could attach a blade to that and swish it round, perhaps as a defensive move while being closely chased by an opponent.

A squirrel is sufficient weapon in its own right. In violation of normal StackExchange protocol, I won't summarise the link because spoilers, and, well, just read it and it'll improve your day, OK? :)

Neighborhood Hazard (Or: Why the Cops Won't Patrol Brice Street)

In case anyone doubts this testimony though, the Daily Mail has headcam evidence of a squirrel getting in someone's face for no particular reason.

Road rage! Territorial squirrel lays claim to bike by scampering over handlebars and attacking cyclist's FACE when he gets too close

More seriously, I wouldn't rate throwing weapons because they don't have the bodymass to launch anything that's more than an annoyance. Acorns might sting, but they're not going to knock you out.

Thing is though that anything they carry will slow them down, and impede both attack and escape. A more natural approach would be a school of martial arts based on assessing the weak points of your opponent (particularly ways into any armour) to get right in close and do maximum damage when they get there. It's hard to stab or shoot a squirrel if it's running round the inside of your body armour! And then of course they're trained for where to find major nerve clusters, tendons, exposed veins/arteries, all that good stuff which will incapacitate a victim in very little time with nothing more than sharp claws and teeth.

I see them using tons of poisons, in order to fight much larger opponents. Find the right plants, mush it up, and use some sort of spear to deliver it, thrown or stabbed. Maybe a ballista if they were organised enough.

It's a practical way they might take down larger prey, be that prey a fox or a human. The kind of poisons you get in squirrel territory might not be on the "poison arrow frog" end of things, so they'd likely attack, then track, if they need to retrieve anything of the target. They would also need use of fire and perhaps pottery in order to have a way of reducing the poisons.

They could potentially be using trapeze-like skills, and swinging attacks on rope, to deliver poisons, something like a very low-tech Attack on Titan.

If you were using plants available in the UK or Ireland, you get the bonus of cool names for the poisons as well.

• nightshade
• hemlock
• monkshood/wolfsbane
• bittersweet
• hellebore
• wormwood

A Nut Gun

Quite obvious, really.

Swords, needles, bees, axes, just about anything from Redwall or Mouseguard.

But with a realistic squirrel, that is harder to say. They do have opposable digits, but I'm not sure how they'd be with gripped weapons. A spear in the mouth will, unfortunately, be useless anyway I can conceive of it.

They could probably throw stuff, squirrels love throwing things. That does give me the impression that, if necessary and intelligent, they could learn to fight with hand weapons. They could walk with three legs, having a sword in the right forepaw, or they could learn to walk bipedal.

Of course, squirrels are so terribly fast, they could run on all fours, grab and bite onto the enemy, then quickly pull out a knife and start cutting, changing position and repeating as needed. Against enemy squirrels, it's be a lightning quick pounce, then the knives come out. If the knives can also be thrown, bonus.

Though spears are a real possibility, in squirrel vs. squirrel combat (choosing reach and killing power over four-legged mobility). They might even be able to load a crossbow if they used their teeth or something.

Definitely a Garrote. Just look at how nimble squirrels are, how easily they are able to navigate around tree trunks; one could easily trail a strong cord and run around prey to do any number of things, including tripping them up, tying together their limbs, muzzling, and even strangulating them.

They could work if groups of squirrels work together to “net up” a large animal, darting in and back to a safe distance.

Just pulling a cord (held in the jaws) avoids all the issues of weilding weapons in the paws or having the body mass behind strong blows.