What you need is a Mine clearance flail tank

Here is a video

https://youtu.be/oQK_a4aGNuc?t=52

These are based on M4 Sherman tanks and still have the standard weaponry in addition to the flails.

Fuel capacity 138–175 U.S. gallons (522–662 litres) depending upon
variant

Operational range 100–150 miles (161–241 km) on road depending upon
variant

Speed 22–30 mph (35–48 km/h) on road, depending upon variant

https://en.wikipedia.org/wiki/M4_Sherman

How would you destroy large groups in the open?

The Soviet RDS-220 hydrogen bomb, known by Western nations as Tsar Bomba, was the most powerful nuclear weapon ever created (...), it also remains the most powerful explosive ever detonated.

This works best if blown up from a few kilometers above ground. Maybe summon it already up.

What about enemies occupying a town when you want to keep the buildings and any innocents in one piece?

You can't save everyone, you'll always have casualties.

Other than that: use a net launcher to snare them:

... Then use drones to drag them into open fields, then:

What about clearing them out of a building without demolishing it?

Once again:

1-)

2-) Have drones drag them to the open fields

3-)

4-) ???

5-) Profit!!!!

Use immobilizing foam to neutralize the skeletons and then the villagers can go in with hammers or similar and finish them off. This will be therapeutic for the villagers in that they feel they are getting to fight back and will ensure total destruction of the skeletons.

To be sure once the skeletons are smashed up with hammers they should be swept up and burnt, ground in mills, or otherwise permanently neutralized.

The trouble when you ask for weapons is that people think of weapons. The sound of Brrrrrt is all very well in context but we're looking at an entirely different problem here. It's closer to toxic waste disposal than combat.

Szczerzo has the right idea when it comes to small scale troubles and building clearances, pitchfork and a woodchipper is the way to go, but once you're in open fields you need something a little more industrial in scale.

I present to you, the armoured D9R.


(Wikimedia)

There's nothing in medieval combat for dealing with something like this in the field. It'll stop a cavalry charge dead in its path, skeletons mindlessly attacking are merely going to turn into bonemeal under the tracks. There may be a few stray hands crawling about the field afterwards, but that's for the woodchipper squads to clear up.

We here, in the Department of Skeletal Removement use pitchforks (and shovels) and wood chippers.

You simply load preferred amount of skeletons on your pitchfork like in the instructional picture below

And then load them into wood chippers.

For the extra sureness of bone removements you can sprinkle them with phosphorus or fluoride

Always follow the safety rules and wear face mask. We don't want to inhale the bone flour. It itches in the throat for days.

Shrapnel is your friend

A skeleton is in many ways a similar target to the types of barbed wire fences used in fixed defensive positions. While you can pound them with artillery and mortars, the most efficient way to create breaches in a barbed wire obstacle (if you can sneak close enough without getting shot) is with a Bangalore torpedo - basically a long, thin tube of metal filled with explosive. This is designed to produce long strips of shrapnel flying through the air to cut through any barbed wire in the vicinity. They would do a dandy job on animated skeletons. (If the protagonist cannot visualise the actual manufactured piece of kit, they are easily improvised in the field with det cord, plastic explosive and three star pickets (the same type of star pickets used to create barbed wire fences, ironically enough.) Lure as many skeletons as possible into a prepared position and initiate the charge from under cover.

If the protagonist must engage directly then she must remember one thing - this is not a video game and she only has one life. Against dozens to hundreds of enemies with longbows she will get unlucky sooner or later if she gives them any chance to hit her. So she must stay out of range (up to 300m for longbows) or in effective cover always and never expose herself to the possibility of being hit with incoming arrows. In case something goes wrong, she should get a helmet and body armour.

Engaging an untiring enemy that is difficult to hit effectively in a series of hit-and-run battles from over 300m away will be challenging. In order to be able to withdraw quickly while carrying significant weaponry and munitions a 4WD is definitely required. (Tracked armoured vehicles require significant training to operate safely and effectively, so they are not a feasible option.) My personal suggestion would be a HMMWV with a Mk 19 grenade launcher mounted and as much 40mm ammunition and fuel as can be carried. Whenever possible she should engage the skeletons from high ground and during periods of rain, both of which will have a significant negative effect on longbow effectiveness but will have minimal impact on the effectiveness of the grenade launcher.

So that takes care of open ground tactics. As for weapons and tactics for when she is going to single-handedly take on the armies of darkness in streetfighting to rescue the innocents - she must never do that. Ever. No matter what. Because if she does she will die. If it is essential to go house-to-house then conjure up a bomb disposal robot (replacing the disruptor with a shotgun) and send that in using remote control. Or she can drive to about 300m away and fire prac rounds through the Mk 19 instead of HEDP if she can get clear shots, that way there is at least no fragmentation to kill friendlies.

Can you summon a vehicle? If so, a steamroller seems the easiest. Drive over them, watch the dust fly away.

Otherwise I would just summon a 40mm grenade launcher or perhaps a mortar, conjure up ammo and you are good to go! A first salvo will shatter the hit skeleton and make the surrounding skeletons fall apart or to the ground. The next salvo's will make them even less dangerous. Repeat till destroyed. Mortars also have the advantage of no LOS firing. The biggest advantage is how extremely simple these things are in comparison to most other weapons.

Or perhaps shotguns. Shotguns can tear bone apart, and automatic shotguns would basically function as ranged hammering on the skeleton.

A demolition crane would give you the relative safety of not engaging the skeletons in close combat and the tool to crush many bones in one simple move.

The disadvantage is than the crane cannot move very fast (although it's not very slow either), so she needs help against big groups.

• Swiping the cranes head in an arc closely above ground can be used to knock enemies down


• Helpers with pitchforks, nets or Tim B's proposed foam guns can keep the enemies away from the crane while it crushes one after the other in quick succession.

Pros

• No ammunition or supplies needed during a fight


• destroys bones and armor alike


• attacks quickly and efficient


• several meters reach and not stationary


• Protected against arrows and other weapons


• Can be utilized for different attacks like throwing boulders at enemies as well

Cons

• Helpers needed to fight larger groups (or you risk being overrun)


• Not very agile on the battlefield


• Vocal communication difficult because of the loud machine

Forget military equipment, use construction equipment.

A fleet of back-hoes to dig pits, bull dozers to shove them in, Dump trucks to drop in asphalt, you have a public works project that solves your problem for both roads and armies.

The hot asphalt dropped down after the skeletons were pushed in would stick them together, trapping them in, if any were able to make it out, the bulldozers could take care of them. Or, steamrollers could flatten them. Mace-men could handle any that slip past, or climb up onto the vehicles.

Plus, it adds a bit of comic relief to what could be built up as a terrifying situation.

For large scale destruction using bombs would be effective but it wouldn't completely destroy any skeletons they hit so i would suggest attempting to capture them and then either powder-rising them with a car compactor, something of that ilk or chucking them into an incinerator therefor completely destroying them which is what you want to do. for smaller spaces like a town... create a small ramming device that can be held that transmits a force into a target it is in contact with pulverising it. other than that, high velocity spinning blades that pulverise anything they touch, or just break it it don't mater, the objective is to destroy not injure until dead like a human.

If (like the question suggests) the protagonist understands enough about A.I. and robotics, I would conjure up some terminators (T800; the liquid metal of the T1000 and such is most likely something the protagonist does not understand, mostly because I doubt it is possible).

Terminators are robust enough to take a beating and more than strong enough to pull two bones apart (no need to break the bones; a single bone cannot do anything on its own, it needs to be joined to another to actually do things) even without weapons. Arm them with melee weapons and the terminators become even more destructive.

As for putting the terminators to work, they can go into buildings to clear them, run around the fields to attack large groups of skeletons, basically anything a human can - just much better. And if defeated, you know they'll be back.

Added advantage: once the skeletons are taken care of, the protagonist won't have to explain where she got that strange magic device she used to take care of the enemy, because she simply got help from an army from across the mountains (or sea, or whatever you want). Sure they look a bit strange, but they look human enough not to cause suspicion in the aftermath. Unconjure them (or keep a few and rule the lands) and you're done.

First thing that comes to mind is chain shot. Two cannon balls joined with a length of chain. Originally used to bring down the masts of sailing ships, I imagine a volley of those through the middle of a skeleton horde would do sufficient damage that the shovel-and-cudgel brigade could then wade in for the clean-up work.

Bludgeoning weapons and basically any high-powered explosives. Sledgehammers should be pretty good at breaking the bones, and enough TNT can reduce skeletons to piles of white powder in seconds.