Are swords, spears, and arrows that turn slain enemies into pure gold useful, in medieval combat, or are they useless aside from free money?
Notes about the weapons:
Honestly, the best use of this would be to turn corpses (their and yours), waste, and the like into nice safe gold. Campaigning armies in medieval times suffered greatly from disease, and poor hygiene was a major part of that. The fewer dead bodies and other disease-spreading elements you have about, the better off you'll be.
Assuming they are rare or entirely new, even a single one of these weapons would turn the tide of any war, but it would never see battle. Just follow these simple steps:
1) stab a few cows
2) hire all the mercenaries
3) capture whatever important places your mercenaries can reach
4) enjoy your new kingdom
This will continue to work until the market becomes flooded with gold, so it's important to never show the weapon to anyone who doesn't understand basic economics. But if its use is well regulated, you can go around hiring massive mercenary items for years.
Assuming these Midas weapons convert a person into a statue of that person made of solid gold, we are looking at a pretty effective weapon in certain specific circumstances. A person, on average, has a volume of 95 liters. 95 liters of gold weighs just over 1800kg. A typical car weighs about 1500kg for comparison. So these weapons will be extremely effective in situations where the sudden addition of ~1750kg of weight would be catastrophic.
Imagine you're laying siege to a castle. You fire some Midas-tipped arrows at the men in the hoardings. Most of the arrows do absolutely nothing, sticking in the wood or bouncing off the stone. But one of them finds its way in one of the arrow loops and hits a defender in the face. He's killed instantly, and suddenly weighs 1800kg. These hoardings are temporary structures built on the walls to provide a wider field of fire. Because they're temporary, they're not that well-built. They certainly aren't made to handle a sudden, localized addition of 1800kg. The floor below him immediately buckles. As he falls, his arms smash the supports out from below him and a ~5-10 meter section of the hoarding collapses.
Here's another scenario. You're defending in a siege this time. The enemy tries to use ladders to scale your walls. You equip some of your men with Midas weapons. They kill the man on the top of the ladder. One of two things happens. The ladder might just snap immediately. Or the man may fall backwards, knocking anyone behind him off the ladder, smashing any rung he hits on the way down, and killing anyone he lands on. Now your enemy brings a ram up to the gate. They easily break it down. Your men take their positions in the gatehouse, again equipped with Midas weapons. The first few foes they kill will quickly block the gatehouse; there is no way they move 1800kg statues out of the way, certainly not while your men are there fighting them as well.
Can i make a good use of this magic for medieval war tactics
Not really. People are easy to wound, but surprisingly hard to instantly kill.
or its useless aside of free money?
All that gold is heavy (making it really hard to transport afterwards), and flooding the economy with so much new gold will cause rampant inflation.
The "Midas" sword is an immensely powerful upgrade to siege engines. For example, a counterweight trebuchet can be used to launch a corpse at a fortification. At the exact moment when the corpse leaves the sling, some mechanism brings the "Midas" sword into contact with the corpse. The 85kg corpse becomes a 1640kg gold projectile (~85kg is the mass of a typical trebuchet projectile). Yes, free kinetic energy! For comparision: typical modern day conventional artillery delivers around 1000kg of ordnance per minute.
The use of a siege engine with a firmly attached "Midas" sword and an effective combat range of possibly 250m ensures that any "Midas" sword/knife/arrow things will be kept away from the enemy. A "Midas" arrow might, of course, be a single-use device, but if it only injures an enemy, the enemy (or one of his fellows) can grab it and use it against you. That would be about as funny as throwing a hand grenade at an enemy with the safetly still on.
Obviously, every alchemist in the kingdom will be researching how to upgrade "Midas" swords to a version which turns corpses into tungsten.
Or uranium. I presume one alchemist was successful with plutonium, but he didn't survive his discovery.
Even without the option to yield "weapon-grade materials", "Midas" devices producing gold isotopes, like $^{201}$Au, might be useful for the more "strategic" purposes. $^{201}$Au has a half-life of around 26 minutes and will turn into $^{201}$Hg via $\beta⁻$ decay.
Tactically speaking, I don't know that that's particularly helpful. Yes, you would certainly be able to make a wall of golden corpses, and yes, you would definitely be rich after a good slaughter, but it's not a terribly useful magic for weapons. I would think it would get in the way, having a battlefield full of oddly posed golden soldiers, probably with sharp objects sticking out and ready to stab passersby (like you). One thing you might be able to do, if you're dastardly and need a plot twist, is to set up your magic-sword character on the wall of a castle under siege. If the enemy is at the gates and all the defenses are exhausted, your reluctant hero could potentially make the dark hero choice to murder his companion(s) with the sword, chuck the golden corpses into the vats they'd used to boil the oil they presumably already poured down on the invaders, and drench the enemy leader in molten gold, perhaps saving the castle and giving the hero lots to be moody broody hero-y about. That's a very specific scenario though.
In the realm of psychological tactics, a weapon like that could be huge. Depending on how common magic is in your universe, a weapon that turns the slain into gold could be a massive psychological factor in war. Just imagine coming up to a village, all the buildings torched, everything in ruins, and finding your fallen comrades, forever frozen in their deaths, in gold. You could set up the dead as statues, warning their people of the consequences of challenging you and yours. Then, they have the added conundrum of what to do with their fallen comrades. Do they bury them? Melt them down for coin? How does one cremate a golden statue? And then there's the religious question as well: what happens to one's soul if one is turned to gold? If your enemies are religious, knowing they might be turned to gold could give them pause in considering war.
Gold itself would not be used to back a currency in this world because anyone with a Midas weapon could make more of it too easily. As such silver would likely be the currency of choice, and thus turning enemies into gold would not yield free money. Also, as I will explain turning stuff into gold will actually cause the war to cost more money.
As mentioned by others as people are struck by these Midas weapons they will turn to gold. Even if it only caused their outer garments that were struck to turn gold this could still pose problems. Gold is a soft metal when compared to other metals, but is heavier than iron. Here are some examples of the kinds of problems: - Plate mail and swords: Become heavier and softer - Leather and cloth armor: Become rigid heavy death traps - Shields: Become too heavy to hold up - Chainmail: Becomes heavy armor with every ring being a weak point which could pull apart
With Chain mail if each ring was considered a separate item for purposes of turning into gold, it would likely become the favored armor of choice against Midas weapons. Only the area struck by the weapon would turn and result in only a minor compromise of the armor's strength with each blow from the enemy.
If enemies in their entirety become gold upon strike this would result in some amount of scorched earth. Any enemy that is converted to gold would mean that their weapons, armor, clothing, food, and other utility items they are carrying would become gold too and thus no longer would be useful for an on going war. This would drive up the cost of war, and with gold not being an acceptable currency would increase the financial burden of the war.
After World War II bomb removal squads had to go around and find unexploded munitions and carefully remove them. In this field if a bunch of Midas arrows were fired on an enemy unit some of the arrows would have missed their mark and ended up stuck in the ground. All these unused arrows would need to be recovered, lest they accidentally kill one of your own people when someone accidentally steps on the arrow head or a kid pulls one out and pokes someone with it. This would cost time and resources.
After a battle is over the field will be covered with golden corpses. Burying and burning dead corpses is typically straight forward, but if they are turned to gold then it is going to take more effort to clean it up, which again will cost time and resources. Luckily though a lot of this could be mitigated since craftsman likely would be willing to take the gold as decorative material, but it will take some time for them to haul all that gold out of there. It would mean your cities are decorated in lots of gold or the roads would be made out of gold.
With people turning into golden statues on the field would cause changes to combat tactics. First mounted combat would quickly die down. Golden statues would create a dense area of hazards which would make it very challenging for a horse to move quickly through.
Second as enemies turn to gold it will cause the battlefield to turn into a maze of golden obstacles. As such the field of combat would quickly expand out as people tried to get out of the more densely packed golden zones and thus a larger area would become the battlefield.
Third, enemies will fire Midas arrows back. If I was laying siege to a castle where the archers were firing Midas arrows at me, I would make sure my forces had good cover and were spread out as much as possible. The goal being that as cover was turned to gold Midas arrows that hit it would not activate and with my forces spread out more arrows would hit the ground. I would then have my forces collect those arrows, at which point I would be inclined to return them to sender.
Flooding the market with vast amount of gold is going to be make gold lose much of its value. First reason not to be fond of using them.
Second reason: on a close combat range, it can happen that the killed enemy corpse falls on the fighter at the end of the combat. Removing a 70 kg corpse is difficult. Removing a ton golden corpse with no help is going to be impossible. Also, you don't want to scatter the battlefield with shiny heavy boulders hampering your troops' movements.
Therefore the tactical usage you can do of this weapon is simply as cash machine: when you need money, just use a knife or a small blade to kill a small animal and cash a small amount of gold. If it works on wood you can also stab a log.
A major problem would be cluttering the battlefield.
Unless the Midas users are purely on the defensive, gold bodies would cause a lot of trouble for movement. Dead bodies are bad enough, but they're not necessarily slippery and can be kicked or moved without breaking a foot. With gold, kicking a dead arm would be like kicking a boulder, trying to shove aside a body to save a companion would be nearly impossible. Stabbing someone in the chest as they charge you will have you under several hundred pounds of gold.
Even if you are fighting defensively, once you get enough gold bodies piled up any attempt at attacking fleeing enemies is gone. It would be impossible to climb over them. It would also make attacking them extremely difficult, but it reduces the choices for the defenders.
So these would not be very useful.
Does it only work on humans?
As in, if you jumped on top of a war elephant and plunged the sword into its brain killing it instantly, would the entire elephant turn to solid gold?
How fresh does the corpse have to be? Could I go to the local cemetery and turn it into a mining operation?
How does the process work? Is it instantaneous? Do I run the risk of having my sword stuck in a gold statue? What happens if I kill someone with my deathblow but the sword gets stuck in a rib or piece of armour then the corpse turns into gold while I'm trying to pull it out? Does the corpse turn into a solid block of gold or only the structural parts of the body? So if a gold corpse was sawed in half could we see gold organs, bone structure, fine gold powder where blood was? That would certainly make transportation easier as it would be easier to make the corpses into smaller parts. I'm assuming too that the body gains weight to match the denser properties of gold though it might be that a person who weighs 75kg is turned into 75kg of gold, not hundreds of kilos.
What about wounding someone first? If I cut off an enemy's arm without the injury being fatal and then take his head off, does he still turn to gold? Other than his arm on the ground of course.
I do see a big logic flaw in this. If only deathblows work to turn people into gold, but corpses can also be turned, then why fight with such a weapon? Why not just show up after the battle, find a few corpses and there's your gold? You also vastly reduce the risk of dying.
It would be better if only the living could be converted as the sword requires living matter to work. If corpses are fine too, then like I said above, you could raid cemeteries for gold resources which seems too convenient.
There's 16 good answers to this already, but I'd like to throw my ideas into the mix as well.
First, I'd like to dispute the fact that unlimited gold would tank the economy and ruin everything
The most basic guiding principle of any economy is that Things are worth what people believe them to be worth. The concept of price changes due to supply and demand is a relatively recent one. Modern humans know to be on guard about the economic effects of obtaining and trading a huge amount of supposedly scarce resources. Pre-industrial humans much less so.
The idea that gold would instantly become worthless is one borne off traditional economic assumptions that information is free-flowing and instantaneous, and people have perfect information. In a mediaeval context neither of these things are true. So while, yes, gold would become devalued in the long run, there is plenty of time in which to exploit man's greed for gold and reap huge economic benefits.
As the king of a small sovereign state with a single Midas sword, this is what I'd do:
Use it for executions.
Keep its existence hidden as much as possible, and wrap the process of turning criminals into gold into a ritual with a whole lot of religious mysticism.
Use the first 'batches' of person-gold to forge alliances with neighbours and hire mercenaries if the setting allows.
Just like the modern diamond trade, you have essentially a monopoly of large amounts of gold and can artificially restrict the supply while trading initially small but slowly increasing amounts of it.
Eventually, when my position is secure enough, I will start decorating the city with it. Let it be known far and wide of the Golden City, the new hub of trade, wealth and Philosophy. Once a place is established as the must-go location for trade and pilgrimages, that reputation sustains itself.
Some practical military uses for gold
Gold is almost twice the density of lead. While it is considered a soft metal, a club made from gold is still going to hurt like hell. Furthermore, there was good evidence in ancient treatises that lead projectiles thrown from slings were especially deadly, owing to the density and lack of air resistance from a small lead sling-bullet. Gold sling-bullets would presumably be even more lethal. If gold can create a military advantage, I say use it!
I think a 'Midas sword', if used judiciously, sparingly and secretively, could be used to great benefit to the Ruler in the right circumstances.
Having your fellow soldiers die next to you on the battlefield is already pretty traumatic, but at least it's not too hard to convince yourself they're at peace now, and often to "help them along their way" by burying them or having some other ceremony to dispose of the body (I've seen quite a few examples in fiction where one side asks or both sides agree to be allowed to bury their dead, which is a whole lot less practical here).
Now imagine they were to instead be frozen in place while screaming in pain. Are they dead or are they somehow still alive in there, forced to feel that pain and unable to move as long as the statue stands? If they're still alive, is there a way to reverse the "goldification"? Also, imagine the conflicts if one person thinks their thoughts are frozen and they can be brought back somehow, but another thinks they are in a constant state of unbearable pain and leaving them is just prolonging their suffering.
What might be even worse would be having to go back to the battlefield tomorrow and seeing them exactly how they died and unable to do anything about it.
Not only that, but the battlefield might still be scattered with the dead of the last army who tried to attack you.
Additionally, any given soldier getting hit on the battlefield could run around screaming, crying and begging while they slowly turn to gold.
This could very well destroy the morale of any enemies you might have.
If you turn anything into gold with one touch, that would likely change the battle to focus more on avoiding getting hit.
Soldiers would prefer light or even no armour.
The enemy might focus more on sneaky tactics instead of facing you on an open battlefield.
A few arrows would destroy any tight formation (since it would be kind of difficult to hold a formation around some giant blocks of gold), so the enemy would be more thinly spread (either initially or eventually).
Any sort of constructs (catapult, etc.) would get disabled in one touch, so those would be virtually useless.
Some of those things might only be good for you if you know how to take advantage of it (assuming the enemy is at least somewhat well-prepared).
Although it might create more havoc, confusion and demotivation to mix Midas and regular weapons - focus the Midas weapons on what regular weapons are typically weak against.
Would the weapon turn liquid (e.g. water) into gold? If yes:
Take some enemies charging through ankle-high water.
Add one arrow.
Get a bunch of enemies who are stuck in place.
Although this would be more of a one-off trap.
Or launch a giant ball of something very light over your enemies - shoot an arrow at it while it's in mid-air to turn it into a giant ball of death.
While the use of gold is arguable, I would suggest something more readily convertible to supplies or directly useful such as cattle or iron, it definitely has its uses to turn a body into something solid.
Fast fortifications
Who said the bodies need to be converted at the place they died? You can build castle-like fortifications super-fast and cheap from bodies. If you are evil, friendly bodies will do, either already dead civilian populace from old age/disease or drafted for "building fortifications" (not disclosing the real meaning).
This tactic could be used even on battlefield for quick makeshift charge defense or other defensive maneuvers.
Military engineering
The building potential of readily movable solid material is not limited to fortifications. Enemy burned bridges? Build new one within minutes from their bodies!
Artillery
Assuming same process would work for other living creatures, birds more specifically, you could mount powerful artillery strike against enemy positions even in pre-gunpowder era. Either mass released or trained birds (=smart bombs) killed by Midas arrows or some kind of timed mechanism would turn into deadly projectiles.
Naval combat
Few tons of solid gold on board of enemy ships? Sounds quite powerful. Either delivered from your board and converted later or turning part of their crew.
This would be useful for controlling the battlefield. If you kill enough enemies in the right places, you can build barriers.
There are limited tactical implications
Gold is heavy. Turning flesh and bone to gold, by volume, is a local violation of matter conservation. That is useful for making (say) cannonballs - cannons having been invented in the 13th century, they're medieval - and you could also in a pinch use it to create projectiles for catapaults, or similar use in other siege weaponry. It's not very good for building barricades, because it's so soft.
If many Midas weapons exist, gold is cheap
Gold and precious gems were valuable because they were pretty, yes, but also because they were rare. Flowers are also pretty; the one time people kind of sort of used flowers as money was notable for being completely out of control (the tulip bubble).
If too many people have these swords, there will be so much gold that it will still be useful - it looks nice, it won't tarnish - but gold won't be gold in this world. It will be more like costume jewelry.
If few exist, they are too valuable to risk deploying
On the other hand, let's suppose that there are (say) three of these weapons in the entire world, and forging them is difficult. Then the problem is this: Using these for military purposes means putting them in harm's way. Deploying them to any kind of front means a significant risk that they will fall into enemy hands.
This is bad, because gold is still valuable enough that capturing the weapon will be a big boon to your enemies' ability to kick your butt. Therefore you will do better to build your own war chest with the weapon, in a secure place far removed from any battlefield. In fact the exact location of the Midas weapon will probably need to be a secret. It's a big target, those invite raids and thieves.
I cannot see any world changing event (except, of course, that gold would be officially worthless) but it would have interesting tactical side effect, mostly because of gold high density
The density of gold (weight/volume) is almost 20kg/l.
Assuming that the volume of the body is unchanged, an average dead body would now weight 1500 kg.
If the poor guy is dead before he hits the ground, you'd better move backward before he crushes you.
In a foot battle, this could be used at your advantage as people next and behind a slain enemy are most likely also enemies. A good kick can make the deadly gold statue fall on them.
Also, a wall of dead bodies would make a very good defense
Imagine the enemy cavalry is rushing at you and you have those magic arrows.
If you make an instant kill, the enemy knight is now a large mass of dense metal tumbling amount your lines. Bad, bad idea!!!
Even worse if you kill the horse.
If you are the guy on the horse, shooting those arrows would be fun, but don't use such a spear. If you're rushing at 20km/h in a soft 70kg mass of flesh that instantaneously turn into a 1400 kg mass of metal, it might hurt you a bit.
LOL
I'm supposing by "useless" you mean "useless to the story".
A lot of the answers here are worried about hyperinflation from production of gold. Actually, used correctly, it could be used to stimulate the local economy, institute development and so increase the wealth of the local lord. But to become that lord... more on that later.
Firstly, does the weapon really not need to strike a killing blow to work? That would be more magically consistent, IMO, the transformation being driven by life energy. But given it doesn't, where does the gold come from? The plane of gold? What entities might be concerned or intrigued by chunks of their reality being transferred to another plane?
As for conservation of mass, there are various ways to do that, but my preference is that there is a drive from the centre of the slain person's soul, that being drawn back to them, to the surface of their body as each part of them outside-in is replaced by gold-- they become a hollow statue. What's inside the statue? Another plotly question to answer.
So, to take over the locale? The main and ongoing difficulty is keeping the secret. If it gets out, others will be after your sword. How one would find people to kill in isolation would depend much upon your character. I think the question is more interesting for a good or (more likely) neutral type. Do they get a job as a healer? A local executioner?
But once you have your starting capital, you can expand outwards, for example start a "philanthropic" nursing home for the terminally ill (do they exist in this world?), which also provides for the grieving families. Side effects caused by magical conditions are not covered by this policy.
Then you can diversify and reduce the risk from discovery. Get rich in other ways and build power. You have insurance for the time being.
Forget using the gold as money, you could make your army wildly powerful with a Midas Sword! Stab as many cows as you can and bring along as many smiths as you can grab, because you are about to make a shiny golden army that is better equipped than any the middle ages has seen before. Metal in general is a precious resource especially in that age no matter how useless it becomes as a currency.
wooden spears (a weapon widely used by infantry of that age) get sharp pointy golden tips that make them much more effective. hell wood anything coated in gold becomes way more powerful
need high density projectiles and counter weights to launch at your foes? GOLD!
wheels coated in gold to make them far more durable and able to go much further without repairs
golden bricks to make on the go fortifications and defensive positions for your troops
the list goes on about how powerful having an unlimited supply of metal as soon as you need it would be
This weapon has so many drawbacks that I arrogantly declare it 100% useless
Even if there's just one such sword on the battlefield, after 30 minutes of combat you'd have so many metalic, immovable, bodies on the field that you, the user, would be tripping over them to get to the next enemy. A gold corpse can't simply be pushed over, and if you do, it doesn't lay flat in any sense of the word. it would be like filling the battlefield with giant caltrops.
Gold isn't valuable because it's gold. It's valuable because it's RARE (well, that and the fact that it doesn't rust or react with anything, but rare is #1). After each battle the gold market will positively overflow with supply, which means the demand drops, which means the price drops, which means gold is utterly worthless. The steel needed to make a good sword would likely become the dominant coin material.
And we'll ignore the fact that the conversion to gold takes X number of seconds and the killing stroke of the blade over or through your opponent takes Y number of seconds and if Y > X then your blade becomes stuck inside a golden corpse and requires a hammer and chisel to get it out.
And last, if not least, is the fact that so long as people think gold is valuable, you'll have every arrow, lance, javelin, spear, atl-atl, sling, crossbow, ballista, catapult, shuriken, trebuchet, rock, and pigeon in the country aimed at your chest. So long as they can think of a way to kill you without getting in range of your sword, you're target #1.
Yes it is useless. You can imagin a midas sword as todays nuclear weapon. If you are finding nuclear weapons useful for today's war so you do on midas sword on medival era.
This kind of weapon can be a reason for consecutive wars from other tribes. So basically you have to hide it somewhere safe and don't show it to anybody.
Using it in a war can focus all the army of enemy on getting their hand on the weapon so the midas keeper must be a super warrior to stay alive.
The weapon can be a economical power tool so its that much important for a kingdom to not use it as a warfare weapon and putting its ownership on a risk. like todays nuclear weapons.
They would be extremely useful in terms of financing huge armies. But you would be silly to use such assets in actual battle, or even let people know you had them. It would make you a target for every nation or ambitious warlord.
