How would a standard Roman human army fight a smaller army composed of skeletons? The skeletons are strategic and will reassemble if you cut pieces off. The skeletons came from the army, and retain their combat skills and weapons (most likely gladius and scutum shield). However, if you pulverize their bones, or just generally smash them into little bits, they will not reform but can keep fighting. They do need their heads to work. What are good tactics and/or weapons to use against them? Magic use is null, but the skeletons could have a magical weakness. The time is "ancient" Rome, so no modern weapons. Thanks!
Clubs, maces, and warhammers. Blunt force trauma in general.
So instead of a gladius they would use a weapon of the above. Smashing weapons would allow to break the bones into many pieces that would be picked by other soldiers to be disposed off.
Also if they depend on their head to fight then getting the heads off would be smart as you can neutralize their ability to actually hit you. Same with the general skeleton construction of the body. Will they collapse if you remove their spine? What about the rest of the connecting bones...etc.
Hooks. Imagine making some sort of contraption that has a hook on a strong wire that grabs the skeleton and puts then into cages or grinding wheel or something like that.
Archers and cavalry will cease to be useful of course. Also something like a phalanx won't have any use.
Elephants. Well. Heavily armored and armed elephants were a formidable force in the ancient world. You could only defeat them with strategy and I'll assume that the skeleton don't have much of that. So just armor an elephants and let it simply smash the opposing line. Don't focus on breaking the line and moral of the opponent. Just smash them to pieces and start collecting them.
Water. Could them swim? I'd imagine a moat being very useful.
Specialized artillery. Instead of the scorpions and similar ones you would primarily focus on throwing rocks of a certain size to break the skeleton into separate parts.
Perhaps instead of the traditional light infantry of the world you would have bone collectors. A blunt force weapon + a shield and no armor. They go around with sacks and once a skeleton is broken they hurry to collect the important pieces of bone away to be disposed of. If people risked their lives throwing javelins at heavy infantry then collecting bones is not a problem.
I don't think we can answer magic without understanding the magic system. The easiest way I'd say if you can cast corrosive spells or fire spells in such magnitudes as to simply melt the bone.
Skeletons pushed together get tangled up with each other easily. The protruding ribs tend to cross the ribs of other skeletons and once that happens it is tricky for the two to extricate themselves from each other. If you add more skeletons it gets trickier.
Bare foot bones have almost no traction.
A mans skeleton weighs 10-15 kg. That is 30 lbs max.
So we have a formation of very light beings which have little traction against the ground and which will get tangled with one another if they bump into each other.
You will have a long rope, each end tied to a team of horses. You will pull the rope into the front of the skeleton formation, pushing them into each other. You will drag the squirming mass of skeletons into a ditch you have prepared full of wood and pitch. You will light it on fire.
Loose bones will be collected by specially trained dogs, and other regular dogs.
Skeletons are very light - about 10 kg for adult European males. In fact, their equipment is likely to weigh more (gladius, 1 kg; Roman shield, 10 kg). This low weight can be used tactically, especially as they will be rather top-heavy, with almost all weight above their hips.
For instance, two groups of soldiers running with a rope between them could bowl over the entire skeleton army, and soldiers with maces could come running behind the rope to crush skulls before the skeletons could get back on their feet. And no, it really isn't very easy to sword cut a rope suspended in air. If you think this is a problem, use a chain.
Similarly, soldiers with long staffs could knock skeletons over, partnered with soldiers with maces to knock skulls in.
The Roman soldiers could also use water (rivers, lakes, beaches) to strategic advantage. Skeletons don't float, as their density is greater than that of water. Their equipment will make them very unbalanced, since the water almost cancels the weight of the bones.
Muddy or marshy ground will also work. Bony feet are more likely to sink deep into mud than fleshy feet, and Roman sandals are unlikely to fit very well on bony feet, so they have likely been discarded.
The top-heaviness of armed skeletons will also make them very unstable on slopes and rocky ground. If the Roman soldiers could lure the skeletons to attack along a slope or in rocky terrain, this could make a major tactical advantage.
I really like the idea of war dogs chewing up skeleton’s leg bones. It is a pretty entertaining image to me.
The roman military was very adaptable. They consistently revised their tactics and formations to deal with the unique properties of their opponents.
I think that they’d form their units around small numbers equipped with either tower shields and billhooks — a common farm implement in the days of the Roman Empire or flails and heavy iron boots.
Imagine an outer ring of a dozen soldiers with the shields and billhooks. They pull a couple of skeletons into the center of their formation. Then like 5 soldiers armed with flails and boots pulverize the skeletons.
The human soldiers would have the mass advantage over the skeletons. Assuming they have equal strength, the higher mass would mean that the humans would generate all lot more force — proportional to the ration of the square of their respective masses. I think this fact would allow the Romans to push through the skeleton forces and selectively pull them into the swarm of Roman formations.
Metabolic acidosis induces calcium efflux from bone and in the process buffers the additional hydrogen ions. Initially metabolic acidosis stimulates physicochemical mineral dissolution and then cell-mediated bone resorption. Acidosis increases activity of the bone resorbing cells, the osteoclasts, and decreases activity of the bone forming cells, the osteoblasts (Bushinsky et al., 2000)
You forgot about acid.
It is possible that throwing boiling acid on bones can liquefy said bones (good luck with protecting your army during the boiling process). I'm guessing that the liquefied bones will still fight (unless that 'the skeletons can have a magical weakness' comes into play - the inability to morph/shift into fluid figures, or function in a fluid state). Another magical weakness could be: absorption into the earth. What came from the earth, must return to the earth.
If that doesn't work, then the strategic warfare answers are your best bets!
Destroying skeleton is easy, the don't have meat, or tendons or skin that would disurb weapon. When you stab persons leg they might still wak it of. The stab might be just badly placed. With skeleton you have one bone to crush to stop it.
@Willk has the right idea, I believe. Tangle them up! It doesn't matter how strong that pile of bones is, if it weights 20kg it can be pushed around by a child, let a lone a fully grown, fully trained roman soldier. The problem is cheap solutions will probably have unreliable results, so forget the rope and horses.
Surround and collapse the skeleton formation until they can't fight back, then methodically destroy each skeleton one by one.
You have both a numbers advantage and a mass advantage, so use your big, strong, heavy humans to meet the skeletons head on, hold the line, surround them and push them into themselves until they literally can't move. From there you can take your time massacring them however you please, be it crushing their skulls, or tying their bones into a bundle and throwing them into a fire pit, or just breaking their limbs and leaving the torso for later.
Sounds like a stretch? Hannibal did exactly this in the second Punic wars while severely outnumbered. The roman's game plan was to rely on numbers and smack carthague's forces right in the face, so they committed all their infantry to the central fight, and massed in one huge, deep line. Carthage met them with a much thinner front line, but Hannibal held it in person, while also pulling back ever so slightly. Meanwhile his best troops went out to the flanks and not even collapsed but just pushed back the romans. These two things forced the roman center forward and their flanks inwards, folding them into a sort of crowded mass. Then, the carthaginian cavalry rode to the back and hit their rear like a hammer. Suddenly the romans had no place to reform ranks, and they collapsed inward until they turned into a chaotic mosh pit, with no space to flee or even to fight back. Their numbers were turned against them and they were slaughtered. Hannibal's army took 5k casualties, the romans' took 80k casualties, the city of Rome lost every last drop of its manpower and the battle became legend. If your scenario takes place any time after 216 BC they probably remember this all too well.
Your win condition is: blob up the skeletons, compress them to eliminate their ability to fight back, and take them apart one by one.
Your advantages: Your soldiers can hold the line indefinitely while in formation. You are guaranteed to be able to push any single regiment of skeletons back, or, if they are in formation and massed, you are at least guaranteed to not be pushed back unless it suits your strategy. You have cavalry... hopefully they do not (skeleton horses??).
Their advantages: They do not tire, they do not rout, they can not be demoralized. They do not take chip damage, meaning that cavalry will likely be unable to do any damage in a charge against them unless they dismount and go head-to-head, and ranged weapons will not do all that much. They know your tactics (not necessarily your strategy). They do not need supplies and can probably move at night.
- Do not commit everything to the front line.
- Do not overpower the skeletons with manpower, but instead match their numbers
- Keep soldiers in reserve, for reinforcing, catching unexpected enemy movements, but mostly for maneuvering around the battle line to find flanking positions.
- Mold the front lines to your advantage. Push the flanks, retreat in the center, or anything else, but always count on your army's ability to do this.
- Do not let the prospect a singular victory like Cannae bait you into the wrong moves. The enemy will not retreat until it is dusted, an alternate strategy like sandwiching just part of the skeleton army, protecting the sandwichers and moving on to the next skelton mass could be useful.
- Don't let the skeletons surprise you. A nighttime ambush might favor the side that can see with empty eyesockets.
- Terrain: You need maneuverability more than the skeletons. They won't tire over tough terrain, though they will be slowed down.
Drilling your soldiers:
Knowledge is power. Your soldiers should know that the undead are not better than the living. Everything they know for sure instead of guessing will give them certainty, which they need to keep their morale high.
- What does it take to kill a skeleton? Make sure every soldier knows how hard they have to hit a helmet to break the skull beneath.
- What impairs the skeleton's ability to fight? Maybe chopping an arm off doesn't kill the skeleton, but a broken arm won't hold a sword.
- What is a skeleton's weakness? Brittle bones may make for bigger weakspots. Likewise, knowing what won't even hurt a skeleton will prevent unnecessary risk-taking.
- Drill your soldiers on pushing and retreating. Weight alone means your soldiers should win charges by accident, let alone through training.
- Drill other new combat tactics needed to keep enemies that won't feel cuts or slashes under control. You benefit from the fact that they know what tactics the skeletons will be using, so make sure you surprise them with new tricks. Maybe a single man can't kill a single skeleton in a fair fight, but a shield tackle should send the sack of bones flying backwards. Make rugby look like a wet noodle contest.
- Drill every soldier on delivering killing blows effectively. Frontline casualties won't be enough since the skeletons should probably take so few of them. Perhaps doing something like a forced push forwards, causing some skeletons to topple and fall, could give you a chance to kill the skeletons you manage to trample, but it's different from a normal battle versus humans.
And above all, have faith in your army. Your soldiers will not fail you if you do not fail them.
If the humans are aware of the skull based vulnerability, I think they should make short work of the skeletons. There's a bit of ambiguity in the phrasing "standard Roman human army," so I'll present a couple possible interpretations. Of course, to some degree this cancels out, as the skeleton army is only described as slightly smaller. Further, I'll assume the skeletons at least begin the fight unarmed, with the plan of obtaining weapons from their first couple oppenents, as their equipment is not listed -- we'll assume they are pulled from the general population, which is mostly comprised of civilians.
Scenario, Rome itself
Rome, the capital of the Lazio, is a fairly large city of 2.8 million people, with a metropolitan area of 4.5 million. Although it does not have a full military, it has the protection of the Polizia di Stato, a formerly military organization (until 1981). There is also a municipal police force for each city. The primary firearm is the Baretta 92, which should have no particular issue penetrating a human skull. In addition, this is slightly hand-wavey, but officers are assigned two to a patrol car, and each car is armed with a Beretta M12 submachinegun. They also have grenade launchers, for riot control, but presumably those are loaded with less-lethal ammunition which would presumably be ineffective against the undead.
In this scenario, assuming the undead are spotted outside the city, the best plan would probably to get into the outskirts (as far as possible, Europe is pretty densely populated). Although police aren't trained to shoot people in the head, modern firearms should make quick work of unarmed undead forces. I would probably place a row of riot police in the front of the army, with submachineguns very close behind, and pistols close behind that. The strategy would be to destroy the vast majority of undead before melee is engaged, and then rely on the now vastly superior numbers of the riot police to overwhelm whatever remains. I suspect the casualties would be fairly low, but it would still be considered a bit of a tragedy.
Rome and the Vatican
The Vatican, being an enclave city state within Rome would surely be willing to contribute their joint defense. The Vatican offers two potential assets:
- The Swiss guard
This unit is mostly ceremonial, but also provides security. Small force, but I suspect they'd punch above their weight class -- They are armed with the SIG Sauer P220, and the SIG SG 550. I don't know enough about firearms to make claims about the P220, other than the general perception that SIGs are held in fairly high regard. The SIG SG 550 is a select fire rifle that fires NATO 5.56, so it should be even more effective against the undead than the basic service weapons of the police. And the increased range will just mean that the re-killing starts earlier, so further lowering the already low burden imposed on the riot squads. In addition, the Swiss Guard is armed with a number of historical weapons (halberds, some plate armor) which could be distributed to the riot squads as appropriate. I imagine a long heavy pokey thing wouldn't hurt to have.
- The Pope
This asset depends largely on your setting. Presumably, the Pope can bless the weapons of the defenders in some way. Now, this isn't standard operating procedure, but presumably when the dead start to rise, they'll want to try it out. If it works, well, however blessed weapons work in your setting, presumably the friggin' Pope's blessings will amp that up to 11. I'd imagine in the very least, a blessed body shot would destroy the undead. If this has no effect, Italy is a largely Roman Catholic country, so presumably the Pope's presence in a fight against the undead will at least be a morale boost.
So, in either case we'd have to expect these assets to make a positive contribution. If the blessings work, I imagine the undead won't even make it to the human line (maybe a couple stragglers here and then, but nothing to worry about). If the blessing doesn't work, I expect that there will be some casualties on the human side (rendering this still a tragedy), as well as some awkward questions for the Church later, but still a very one sided victory.
Rome, plus the Italian military
Well, presumably the Italian military wouldn't react very well to an army of the undead marching toward their largest city. The Italian military is split into the customary Army/Airforce/Navy setup, with another branch for military police. In particular, the Italian Air force has a number of ground attack jets, multi-role fighters, and, I believe some attack helicopters. You can look at a more detailed list here. And their army has field artillery, tanks, armored personnel carriers, and attack helicopters. Full list here. I think the best plan would be to blow up the undead from very far away. If they can't accomplish that, the Italian people should have some serious questions about where their tax money is going.
I presume since we are dealing with the undead, morale is not an issue for them - these skeletal soldiers will continue fighting until ordered to do otherwise. This makes them very dangerous - in ancient warfare, actual combat was usually a relatively small contributor to the number of casualties. I don't have actual sourced numbers on hand, but I would ballpark that in an evenly-matched encounter <5% of the soldiers would die in the actual fighting. By comparison, huge numbers of soldiers were lost in a disorganized retreat (a rout). The result was that the winning side often suffered relatively light casualties, while the losing side might have their ability to organize further resistance effectively destroyed. (Consider the Battle of Zama, the final battle of the Second Punic War. Rome brought ~35,000 soldiers, while Carthage brought ~40,000. The result: a Roman victory, with an estimated 4-5k lost by Rome... compared to 33-40k killed and captured Carthaginans.)
Since the Skeletons will not rout, any pitched battle between the Roman army and the skeleton army will require the Romans to commit to an all-day grinding slog simply to achieve a stalemate at the end of the day. If we add in that skeletons don't need to eat and don't get tired, the Roman army cannot win a pitched battle, without overwhelming tactical and/or numerical advantage.
Fortunately, the Romans were smart, and there were more than a few very clever Roman generals. If we assume typical Roman ingenuity, they are probably aware of this danger and will avoid pitched battle at all costs. His best hope is to engage in guerrilla tactics. This does go against pretty much every Roman tactical doctrine in the book - Romans were notorious for seeking open battle with the enemy, and despised military deception... which cost them at Teutoburg - but they were a clever bunch and they had a lot of tools that could come in handy here. Things like rolling balls of flaming pitch down hills into packed enemy formations, or launching stones via mangonel or ballista. They even had a ranged weapon which would likely have been very effective in this case: the humble sling is absolutely capable of breaking even living bone ensconced in flesh. Dry, dead bone would likely shatter if hit.
So, taking some hints from other posters: I would expect a Roman army to engage in hit-and-run tactics involving blunt force trauma and extensive projectile use, while trying to lead the skeletons into unfavorable terrain (swampland, rivers, mountains). While this would not destroy the army outright, they may be able to weaken it considerably. Further, any groups that are isolated could be swarmed, surrounded, and beaten into oblivion with clubs/staves/etc. The ultimate goal of the Romans would be to weaken the skeleton army enough that they could gain enough advantage to pull a Carrahe or Cannae on them, or otherwise get at whatever is holding the army together.
In ancient Times, there was Greek Fire -> https://en.wikipedia.org/wiki/Greek_fire They were able to throw them with war machines, so they would not even have to come near to the undead army.
I am pretty sure that bringing the whole army to burn in very hot fire like in a crematorium should destroy them.
Edit: I read that Greek Fire itself was invented around 677 AD, so this would be too late for the scenario. But according to the already mentioned wikipedia article, weapons of fire were used from the 9th century BC, so the Answer should not be invalidated.