# How to sabotage a blacksmith production? [closed]

The city's main weapon and armor supplier has lost his contract arming the city's guard because the quality of the last batch of its products is awful.

The swords break at the first clash, the armor doesn't hold together under a couple of blows. How did this happen? The materials are of the highest quality, the blacksmiths have done this work for years and they didn't notice anything wrong during the process of making the weapons and armor, obviously this shouldn't be happening.

What did the saboteurs do to the materials, tools or finished products that only after delivery they were found useless?

• It'd be ideal if both weapons and armor are sabotaged but it could be just one.

• There is magic in this world, but I would prefer a non magical solution if possible.

• It shouldn't look like a sabotage at all.

• The period is set in Late Middle Ages (1200-1500)

• Sabotaging the process might be possible, but it would take a whomping good bribe to sabotage the blacksmith himself. He'd know about anything wrong with the process and would certainly know that he was producing substandard equipment. I suspect this question is more about the blacksmith than it is the process of subverting the process of blacksmithing. Jan 10 '19 at 4:17
• In Late Medieval Europe creating weapons and armour was already a specialised task, the Guild of Armourers in London was founded in 1322 the Guild of Cutlers granted a charter in 1416. It was also before the days of centralised manufacturing there would be several craftsmen performing those task in a city rather than one, a smaller town one would,be more likely. Jan 10 '19 at 4:45
• "The swords break at the first clash, ... The materials are of the highest quality". Without magic this doesn't compute. The blacksmith will test the blade thoroughly, especially after one or two have been found to fail. The soldiers will test their swords as soon as they receive them - they won't wait for battle before even trying the weapon. Jan 10 '19 at 9:15
• Not enough time to post a full answer, but adding gallium to a batch of metal makes it annoyingly magnetic, brittle, and hard to separate out the gallium. I am sure there is probably something else more plentiful that would produce the same result but I can't think of it right now. Jan 10 '19 at 15:25
• If you'd consider a ret-con to this: "The city's main weapon and armor supplier has lost his contract arming the city's guard because the quality of the last batch of its products was so awful he refused to ship them." is a much simpler premise that allows for all sorts of sabotage to materials and tools that is detectable in the finished product but not easily diagnosed if the sabotage is subtle enough. Jan 11 '19 at 18:08

## Replicas

The blacksmith did his job to perfection - the equipment just never got to the army.

The saboteurs act as middlemen in the delivery system. The carriages holding the gear are intercepted midway and swapped with shitty quality replicas that look exactly like the blacksmith's equipment.

This could work in at least two ways:

1. The saboteurs have a few inside men. At least one of them should be one of the armour/weapon designers that would let the sabouteurs know, in advance, what the gear will look like. The others should be the members of the delivery crew;
2. As pointed by Mason Wheeler, they don't need an inside man to let them know what they're going to deliver, they just need what they deliver to be predictable and routine enough that the saboteurs can anticipate it.

This would also be profitable to the saboteurs, since they could still sell the high quality gear to someone else.

• +1 for giving the only answer I've seen so far that realistically works around the "the blacksmith would notice" problem without requiring the blacksmith to be a saboteur, in spite of what you wrote. They don't need an inside man to let them know what they're going to deliver; they just need what they deliver to be predictable and routine enough that the saboteurs can anticipate it. Jan 10 '19 at 16:08
• 'And the fact that you've got "Replica" written down the side of your swords, and the fact that I've got "Desert Eagle point five O" written on the side of mine...' Jan 10 '19 at 16:54
• This would also be profitable to the saboteurs, since they could still sell the high quality gear to someone else. - Why "someone else"? Why not just set up as another blacksmith in the same town, and sell the armor/weapons to the same city? Jan 11 '19 at 18:43
• @Clockwork-Muse Craftsman have their own unique mark they put on the things they make - the maker's mark would be an instant indication of who actually made it. Obscuring a metal stamped mark would be difficult, so best ship it far away and hope to sell it all before word spreads about the switch. Jan 11 '19 at 19:17
• Also, I don't really think there's a solid reason for these saboteurs take this risk. Their trade is... well... whatever pays good money with the least chance of being caught. Don't you think it would be a little shady that a new shop happens to open up with tons of gear just after a major shipment from another shop was stolen? Jan 11 '19 at 20:06

Heat up the products above the eutectoid temperature to form austenite and then rapidly quench it to induce the formation of martensite. This will induce the formation of hardened steel which is more brittle.

Martensite is formed in carbon steels by the rapid cooling (quenching) of the austenite form of iron at such a high rate that carbon atoms do not have time to diffuse out of the crystal structure in large enough quantities to form cementite. [...] Too much martensite leaves steel brittle; too little leaves it soft.

A skilled artisan will use this process to make the outer of the product hard, but he would do it to the right point, so that the core is left resilient.

The saboteur would just move past this optimum and ruin the final result. A bit like baking a pizza 5 minutes more: from crust to char with the blink of an eye.

• Comments are not for extended discussion; this conversation has been moved to chat.
– L.Dutch
Jan 10 '19 at 19:42

@JBH points out the difficulty. If you provide poor materials the smiths will detect problems because the metal will not act right. Quality control is integral to their line of work. Also, the smiths are not really bribable - it is their livelihood and if they get a reputation for turning out shoddy products that is the end of their work. A bribe would have to be enough to retire on.

Sabotaging the materials after they are made is really hard too. They are steel and steel is durable. Damage enough to make them fail on first use will be readily evident, certainly to the smiths but probably to anyone familiar with such items.

I can think of only one option.

Changeling.

Fairies take human children and leave in their place supernatural creatures who pretend to be children. The changeling children are sickly or weird or spooky. This has to be the solution for the armor and unfortunately, it probably requires magic. Magical entities (though probably not fairies, given they hate iron) steal the finished high-quality arms and armor and substitute pottery items, with a glamour cast upon them to make them look and sound like the originals. Of course, the changeling armaments fail immediately on use.

I like the idea that when someone figures out how to dispel the glamour, the crude pottery items are seen to have scrawled on them dirty words and obscene drawings labeled with the names of various knights.

• A more mundane version of this idea is to hijack the equipment during shipment and replace it. It's a two-fer! You get the good stuff and your enemy gets bupkis. Jan 10 '19 at 6:04
• Intercepting during shipping could potentially heat the equipment and infuse some weakening chemical (or magic?) into it before cooling and letting it on its way to delivery. Jan 10 '19 at 9:36
• A bribe would have to be enough to retire on and to flee. The penalty for military sabotage in a mediaeval society isn't likely to just be loss of livelihood Jan 10 '19 at 9:43
• @ChrisH Sabotaging military equipment is going to put you in serious trouble even in modern democratic societies. We're talking about treason, here. Jan 10 '19 at 11:09
• Somehow I did not think of the alternative proposed b y @JBH because I was picturing it happening under the noses of the smiths. But if the shipment of arms is intercepted and substitute shoddy crap swapped in, that would work without magic. It is out of the control of the smiths and the end users have never seen the items so will not notice a change. That happens all the time in the real world. Jan 10 '19 at 16:42

Adding too much phosphorus to the iron makes it "cold short", i.e. brittle at low temperatures.

The effects of cold shortness are magnified by temperature. Thus, a piece of iron that is perfectly serviceable in summer, might become extremely brittle in winter. There is some evidence that during the Middle Ages the very wealthy may have had a high phosphorus sword for summer and a low phosphorus sword for winter (Rostoker & Bronson 1990, p. 22).

Iron ore

• Two problems with this: (i) the blacksmith would notice, (ii) wrought iron is good because impurities work their way out at least to some extent. If you could continuously contaminate the iron with P or C, and the smith was under time pressure, you may be able to get him to make substandard work Jan 10 '19 at 9:38
• Cut off their source of a few key materials and they won't be able to flux the pot of metal, leaving all sorts of crap in there. Jan 10 '19 at 10:57
• @Mazura they'll notice they're missing the materials. Jan 11 '19 at 1:07
• @immibis - If they're used to using limestone from a specific location, and that becomes tainted or unavailable, and then they have to start using borax, it might take a while to get the process down again. Jan 11 '19 at 1:11
• Maybe they are made in a warm place, and tested after collection, in the same locale - and they pass. They are THEN sent to a war, but the war is in a cold location, and the sabotaged steel - which passed the tests in a warm climate - are JUST - sabotaged enough to be unreliable in a frozen wasteland. Think WW2 - weapons made and tested by the Black Sea, then shipped up to Leningrad for use in the frozen north. Jan 12 '19 at 18:24

## Weaken essential parts instead of the whole thing

My source for all of this is that I work at a historical armoury and have actually assembled/disassembled quite a few pieces for restoration.

I know which damages are fixed easily and which ones take ages. I also know which ones render a weapon/armor useless and which ones don't.

It's pretty easy to discern accidental change from something a person did on purpose - in my case the deliberate changes were made by past restaurators but seeing as their goal is also to not have their work noticed I think the methods would be the same as a saboteurs - only the goal is the complete opposite.

I think it wouldn't be easy to sabotage the actual armor plates or blades. Even after centuries they are still basically unchanged and usable. Any sabotage that effectively weakens a plate would probably be visible or at least discernible as sabotage. Likewise a good blacksmith would notice changed raw materials or sabotage during production.

Also all armor, weapons and especially guns were tested before being accepted by the army. This means that any major faults like a suit of armor breaking on the first hit would be noticed before they even leave the armourers workshop.

Therefor I would suggest to go for the things keeping it all together. After all what use is a suit of armor if you can't fix it to your body?

## Leather straps

Sabotage: Armor, scabbards, guns

You could have them treat the leather straps with oil that has gone bad. This will turn the leather acidic which will cause it to go weak and break.
Upside: The chemistry of why the leather breaks wasn't yet known in the middle ages so it would probably be blamed on the blacksmith using poor materials.

Downside: It takes a few years.
Complexity of fixing it: You need to replace the leather straps - for armor that is complete disassembly and reassembly. Scabbards and guns: quick fix
Source: This actually happened accidentally after WWII when supplies were short and the armouries batch of petroleum had gone bad. This is the reason why there are so few original leather pieces left.
(btw: do NOT use petroleum for leather! Even if it hasn't gone bad it's not a good idea)

## Rivets

Sabotage: Armor, scabbards, polearms, shields

Every piece of a suit of armor is connected to another part or a strap by rivets. If you don't know how handmade rivets in armor works: It's basically a nail that is stuck through a tiny hole in the plate and let's say a leather strap and then flattened with a hammer on the other side.
Your saboteurs could file off that flattened piece of the rivet. Not completely so it doesn't fall out immediately but if it's just slightly bigger than the hole in the leather strap and plate it will eventually slip through with movement which leads to the armor falling apart.

Upside: it would look exactly like shabby workmanship but wouldn't be spotted by a rough inspection
Complexity of fixing it: Depending on which rivet breaks you might have to disassemble the armour completely. Scabbards and Polearms: quick fix
Source: I've seen this happen when we had to replace the leather strap and the new rivet wasn't done properly.

## Hilts

Sabotage: Swords, sabres, daggers...

A sword isn't much use without a hilt. Mostly the blade has a smaller metal part protruding from the back. The crossguard is fixed to that piece and then leather/wood/wire is wrapped around it to form the actual handle.
If the leather/wire is loosened the handle will come apart leaving you with an acceptable blade you can't wield. If the handle is wood the saboteurs could saw off a tiny bit on one end so that it moves a bit between the crossguard and the pommel. It doesn't actually destroy anything but makes the sword awful to swing. If they saw off just a tiny bit it would look like the blacksmith fitted the handle poorly.

Complexity of fixing it: reasonably quick fix
Source: Quite a few handles have loosened by age and some of the wooden handles in the armoury have shrunk giving that loose effect.

## Scabbards

Soldiers don't run around with drawn weapons all the time so sabotaging the scabbards is also worth a shot. You can do the same thing as I described above with the armor rivets.
You could also make slits or holes in the outer layer of leather. It normally prevents moisture from reaching the wooden part inside. If the slit is directly next to a metal band or the tip protector it might look like the blacksmith damaged the leather when assembling it.
Not so much for discrediting the blacksmith but still useful: You can also pour blood or salt water into the scabbard which will cause the sword to rust in its scabbard. (This is the reason why they have to be cleaned before being put back into the scabbard) Combined with a slit here and there and if you're lucky people assume the liquid got in through the slits which would be the fault of the blacksmith.

Upside: looks like the soldiers weren't careful with their weapons.
Downside: rusting takes a few days to weeks - depending on other circumstances.
Complexity of fixing it: if the blade is just rusty: reasonably quick fix, if it is rusted stuck in the scabbard: they would probably cut the scabbard off the blade and make a new one so reasonable to long fix (in the museum we have to preserve both)

## Pole weapons

Most pole weapons are mounted to the wooden staff by metal bands that run down the wood and are nailed to it.
These nails can be loosened quite easily. The can also be filed off a bit like rivets.

Complexity of fixing it: quick fix
Source: Shrinkage of wood over time has caused lots of our poleweapons to have the nails come loose and they have become wobbly.

## Gun powder

I don't know if there are firearms in your universe but if there are your saboteurs might want to refrain from doing the obvious and corrupting the lock. That's the first place one would look for sabotage. Seeing as the mechanism of a flintlock is actually pretty simple any damage would be quickly spotted by a blacksmith as soon as they take the lock off the gun.
Every gun was inspected and tested after being finished so again I would instead opt for the accessories. After all a gun without powder is useless.
It's hard to pin this on the blacksmith though. One way of doing that would be to temper with some of the black powder. If the powder is more powerful it might explode the barrel of the gun. This also happened with poorly crafted barrels. If too many barrels explode the blame will be put on whoever made the powder though.

Upside: if the gun explodes you also take out a soldier at the same time
Complexity of fixing it: an exploded barrel can't be fixed
Source: lots of people have tried shooting antique firearms but they used modern powder. Modern powder is more powerful and explodes old guns.

## Splints

Sabotage: guns

Gun barrels are fixed to the wood by (most of the time) two splints and one two three screws. All of the screws are in the back next to the lock while the splints are placed along the length of the barrel.
Pull out those splints and all the strain is put on the screws. They are relatively small and sometimes go missing on their own. It could either be that the blacksmith forgot them in the first place or made them too thin so they fell out.

Complexity of fixing it: quick fix
Source: So many old weapons missing the splints.

## Bolts and Screws

Sabotage: guns, some swords, some armor

Screw them in extremely tight so there is more pressure on the screw. This might snap off the head or damage the thread if there is some fault in the material already. Damage the slot so it can't be used properly anymore. This usually happens by accident when fixing something but it could also be done on purpose.

Upside: soldiers don't usually touch the screws so any damage to them would only be noticed by a blacksmith who would then know that the one previously handling the object was an idiot who didn't use a fitting screwdriver - discredit the blacksmith among his peers!
Downside: mangled screws are only a problem once you want to fix the object because it has another problem
Complexity of fixing it: very annoying reasonable fix
Source: If the slot of a screw is mangled we actually have to fit a screwdriver to it so we can get the screw out

## Mismatch equipment

Sabotage: swords, guns, armor

Mix swords and scabbards so they don't fit properly anymore. Same with armor parts like the front and back of a suit of armor.
With guns it's even easier because soldiers had to make their own bullets. All of that equipment is handmade and fitted to the barrel - switch it up with another and they don't fit properly anymore.
Also if you take two guns and switch out their locks it might even render the gun completely useless. There is a small hole in the barrel right were the pan on the lock is. When firing this is were the spark from the powder on the pan goes through to ignite the powder in the barrel. Because no two guns are exactly the same the small hole might be off or even covered by the pan if the wrong lock is fixed to the barrel.
If confronted about it the blacksmith himself will probably realise what happened but it's something you can't really prove. There are no serial numbers to show which parts belong together and to a layman they all look the same.

## Conclusion

Some of these will be harder to pull off than others and some have the added benefit of annoying the army blacksmith who has to fix it.
All of these equipment failures would probably happen anyway so with your sabotage you are just going to increase the frequency. Of course if suddenly everything goes wrong all at once people will get suspicious especially if the blacksmith has always delivered quality work before.
None of these are particularly big but all of them show a lack of attention or skill if they happen to fairly new weapons.
So even though the blades and plates this blacksmith makes are actually pretty good he will earn a reputation of not taking care of details and slacking with the unglamorous parts.

Use a STASIS spell to alter the supply chain, and later remove the spell to destroy the weapons.

Replace the Carbon used in the smelting and forging with Carbon-11, which has a half-life of about 20 minutes, but apply a stasis spell to the carbon to keep it from decaying. This could be done by a magic-user placed at the gates, watching for the ox carts filled with coal or charcoal.

The incorruptible smiths smelt the iron and forge the swords with the Carbon-11. It works in the forge the same way. The strength is tested, and the swords are pronounced excellent. They get the martensite profile just right. The swords are deployed to the troops. They work perfectly during training. Against other foes, they work as expected -- they are sharp and subtle, yielding to glancing blows, yet slicing through armor and bone. But -- when the critical battle starts, remove the stasis spell. The swords and armor will quickly become weakened as the carbon turns to boron and the crystal structure breaks down.

There may also be a benefit from the positron radiation emitted by the iron after the stasis is released.

• In medieval times, the carbon used in smelting and forging came from the coal being used to provide the heat. It would take one heck of a complicated stasis spell to permit coal to burn without letting it decay radioactively.
– Mark
Jan 11 '19 at 0:12
• It could be a simpler spell, since it need affect only the nuclus and could leave the electrons to wander at will.
– cmm
Jan 11 '19 at 1:44

Given the answer of Willk, it appears to be unlikely to manipulate the process without the smith noticing it. If you don't want to use magic directly, use something similar instead: Alchemy.

Some mixture has been used for the iron which takes over time with incrementing effect over days or weeks. The initiator could be the heat applied in the forge or the water to cool it off - which means the mixture could be applied even earlier. It would render the metal brittle until it unexpectedly breaks, but given the progress rate it would occur quite rapidly. The blacksmith could not notice anything because the effect is near non-existent in the first days or weeks.

The process wouldn't require some form of "intelligence" which magic would usually contain (do effect x when y is triggered, but not z). It would rather be a fictional chemical process. Maybe something in the real world exists which does something similar or works similarly.

• I wouldn't know how to create something like this without the biochemist in my game telling me that what I'm saying is not possible. If something like this exists in the real world, this definitely will be accepted as the answer, thanks. Jan 10 '19 at 16:15
• Does your biochemist allow you to have rust monsters? Jan 10 '19 at 17:40
• I'm not aware of anything that would work on iron. Mercury would work just fine for damaging aluminum swords, but aluminum is a lousy material for making swords out of.
– Mark
Jan 11 '19 at 0:16

The blacksmiths use a very sophisticated technique to produce their legendary swords that requires repeated forging and cooling. This produces a very special flexible and durable but also very sharp steel.... Unbeknownst to them, the process requires certain trace elements to be present in the ore, and they get this (or more likely wootz steel made from this) special ore shipped from a neighboring country.

The adversary manages to capture some of these shipments and replace it with wootz steel from a different mine. To the blacksmiths everything looks just the same, but the swords are too brittle now. No one understands what has happened.

Note that this has a precedent in human history: There is a hypothesis that Damascus steel got its very special properties from the presence of trace metals in the ore combined with a special manufacturing process. At some point in history the blacksmiths lost the ability to reproduce that steel and this might be because the respective mines in India were exhausted.

Wikipedia: Damascus steel

Reibold et al., Carbon Nanotubes in ancient Damascus sabre (2006), Nature 444, 286

• I can see this working with my setting, I'll consider it. Thanks. Jan 10 '19 at 16:04
• You could get a believable drop from exceptional swords to average swords this way, but a drop from "exceptional" to "defective" would be noticed during the forging process.
– Mark
Jan 11 '19 at 0:15

I'm assuming from your username and the setting details that you're running some sort of D&D or D&D-adjacent system. There's always one answer to that guy who got full plate before he should: the rust monster.

Rust monsters have strong corrosive materials in their antennae, and they're flimsy enough that an enterprising hostile kingdom or well funded crime syndicate could capture, breed, and harvest them.

Your saboteurs will need fairly lengthy access to the caravan to pull this off, but if the arms are coated in some kind of clear coat (varnish, lacquer, whatever - armor should come treated from the forge, but the weapons themselves may or may not be and would be the responsibility of the saboteur - shouldn't raise any alarms to find them coated) and stored with powdered rust monster antennae (in the sheath, on resin paper wrapping the armor, whatever), the arms themselves will:

1. Leave the blacksmith in good condition
2. Survive transit reasonably well, depending on the care taken by the saboteurs
3. Perform well in their initial inspection, if treated gently enough
4. Fail faster in the field if they were used in practice, but should fail eventually if used hard enough in battle regardless.
5. Show signs that look like water damage that could be blamed on an incompetent carman (wagon driver), marshal (officer in charge of transport), or lighterman (ship-to-shore ferryman)
• You are correct this is in a D&D campaign. I'll have this in mind, thank you. Jan 10 '19 at 20:25
• The usual protective coating for iron is oil.
– Mark
Jan 11 '19 at 0:20
• That's called "bluing" the armor, and that's closer to seasoning an iron pan. You quench the hot armor in oil, and it forms a protective coating that...honestly, lasts about as well as you'd expect, given how well a cast iron pan's seasoning lasts if you use metal utensils in it. Maintenance of armor involved a lot of removing and reapplying top coats. Squire duties after a battle would involve wiping it clean, scrubbing it with sand, then reapplying a coat that varied by time and geography. It's the sort of thing that D&D just handwaves over, though. Nothing takes much maintenance there. Jan 11 '19 at 15:53
• (Not to discount the use of oil/grease for lubrication - it's a real thing, and also important for maintenance.) Jan 11 '19 at 15:54

## Quench bath contamination leading to Stress Corrosion Cracking down the line

As other answers here indicate -- these smiths' reputations and livelihoods are on the line here, so their processes would be in good nick and unlikely to change suddenly, and they would likely notice issues with raw material changes, say to the ore, charcoal, or fluxes used. Furthermore, even if they didn't, proofing of the blades (acceptance testing) by the quartermaster would weed out blades that were, say, extremely cold short due to phosphorous contamination.

This means we need to get diabolical here, and look at the things a smith or quartermaster cannot see, or catch immediately with tests. In particular, preindustrial forging relied exclusively on static, water-cooled quenching and tempering processes, and these will leave traces of salts present in the quench bath on the blade as it is removed from the bath (simply from water boiling off upon contact with hot iron).

Normally, this isn't an issue, as the contents of most water sources aren't going leave behind anything that will cause serious trouble down the line. However, if the quench bath was "spiked" with something that was a potent promoter of Stress Corrosion Cracking (SCC) in carbon steels (carbonates may work, depending on their activity at or near body temperature) under mild conditions, this could effectively, yet insidiously, sabotage their efforts to produce quality blades.

As such a contaminated blade was handled and used, moisture from the environment that gets past whatever oiling is used to protect the blade from rusting would combine with the boiled-out SCC promoters in crevices in the weapon, such as at the blade-to-handle interface. Furthermore, such points would also be stress risers in the blade, and combined with residual stresses from forging and heat-treatment as well as the rigors of usage, this could lead to stresses at the risers exceeding the SCC critical stresses for the material. Finally, a well-kept sword is going to be in an environment that is only mildly corrosive (due to normal maintenance activity vs. being exposed to rain, blood, etc).

The end upshot would be swords that look fine, proof fine when received by the quartermaster, yet snap in half like twigs months or years later. A modern failure analysis would reveal that the broken sword was spiderwebbed with invisible yet lethal cracks in key spots, despite looking the part of a well-kept sword by any account chosen.

• "carbonates may work" - Which carbonates are you talking about? A hand full of soda ash? Toss in a few TUMS? Doesn't matter? Jan 11 '19 at 0:59
• Any residual salts from the quench bath are going to be removed the first time the sword is cleaned.
– Mark
Jan 11 '19 at 1:59
• @Mazura -- soda ash would likely be the best choice, yes Jan 11 '19 at 3:17
• @Mark how? Swords are generally wiped down and oiled, but not, to my understanding, washed or otherwise cleaned with water.... Jan 13 '19 at 18:30

The saboteurs entered the blacksmiths guild. With some help they ascended in ranks, becoming the guild masters. They transformed the guild in a company with employed blacksmiths. They added a huge bureaucratic top-layer: Accounting, human resources, quality control, sales, marketing, R&D, supply chain management, legal and controlling. The blacksmiths got gradually replaced with inexperienced workers. The work got compartmentalized. As a result workers are unable to understand the entire organization. Then they started with quality degradation: Controlling argued that the contracted quality could still be meet while introducing inferior raw materials (iron ore rich in phosphor and sulfur). R&D had is scope changed to focus on lowering costs. Supply chain management squeezed every penny from the suppliers, resulting in raw material degradation. Legal sued the local news herald when they mocked the inferior quality.

When the city council became concerned about the degrading quality sabotage got further.

The saboteurs argued that city help is needed as competing cities are advancing in iron processing. They asked for import tariffs and city subventions and got them. They introduced a city-financed institute for advancement in iron processing. The council pressed the city council to force independent manufacturers into the iron conglomerate. The blacksmith school got incorporated into the iron institute and replaced by cheap least minimum training. The institute declared that the brittle iron weapons/armor parts are state of the art, opposing opinions got suppressed by libel charges and by media campaigns, accusing them to be non-patriotic.

In the end the entire iron processing ability of the city got corrupted. Since nobody realizes the dimension of the degradation it is unlikely that the cities iron processing ability will ever raise to past quality.

• HR, R&D, corporate, etc. in middle age?
– L.Dutch
Jan 10 '19 at 10:25
• It sounds like something between Orwell's "Animal Farm" and the revolutionary claims of that peasant in "Monthy Python and the Holy Grail". Jan 10 '19 at 11:07
• @L.Dutch The first recognizable corporations were formed in the middle ages. If memory serves, the first one was to develop a system of dams for harnessing water power for milling. Blacksmithing actually lends itself to this because, in spite of modern stereotypes, medieval smithing of is not really solo occupation - it takes a staff to keep the smithy functioning at peak capacity. Jan 10 '19 at 14:40
• @pojo-guy, I doubt medieval corporations had HR, accounting and all the circus..
– L.Dutch
Jan 10 '19 at 15:15
• @pojo-guy The detailed organization can end at shop level, with each smith responsible for the smith's shop. It's useful to have some sort of guild structure above that, but each blacksmith will be an independent business and will know what's going out of the shop. BTW, the "cheap on-the-job learning" is termed "apprenticeship", and is the standard way someone would learn to be a smith in those times. Real blacksmiths would sound the alarm on quality degradation, so it could not be done in any way quietly. Jan 10 '19 at 16:29

One option could be a poor quality ore the blacksmith was working with. If the ore had an excess of one metal or another to give it unfavorable qualities, then it may be possible the final product would fail. If it had excessive amounts of lead, tin or copper, the weapon would be too soft and deform easily. If it contained excessive amounts of nickel, cobalt or tungsten, the armor would be too strong, thus brittle and may crack upon receiving a blow.

Now, any good blacksmith would recognize that the metal is not tuning out as expected, however, if he had several apprentices, they may not recognize the poor materials and force the piece into the desired form despite the material not wanting to play

Not the most effective way but an interesting mythological occurrence of this by Loki can be read in places like here https://norse-mythology.org/tales/loki-and-the-dwarves/

The short version of this is Loki turned into a fly and distracted the dwarf who was working the bellows in an attempt to sabotage their attempts at crafting.

Transforming into a fly might not be a reasonable method but unleashing a plague of rats/vermin/sickness on the workers at the smithy could slow down their production, cause them to cut corners and release shoddy work.

The iron used to build everything (weapons and armors) could've been saboted by adding more carbon inside, before being sold to the blacksmith. If more than 2,11% of carbon is added to iron, it becomes steel and isn't as flexible as the iron. Then, it will break.

But if you have magic in your world, why not think about another material than carbon added to iron, which degrade it slowly (for the blacksmith not notice it) and make weapons and armor bad quality faster (degradation appears after the first fight you said).

• The problem with this solution is that the blacksmith would know instantly that the metal was bad. You're correct: up to 2% makes steel. Add just a bit too much carbon and you end up with pig iron --- strong but brittle. You can't add much more than that as I've read iron can only take so much carbon. A smith will Know, because the pig iron will literally crumble when he starts hammering it. He'll never be able to make a weapon from that. Jan 10 '19 at 5:02

Some techniques for differential hardening of blades (wherein the edge is very hard, while the core of the blade is more flexible to provide strength) involve the application of clay along the center of the blade before the final hardening. If your saboteurs tampered with this clay and changed its characteristics, it could lead to a blade that looked right, but was actually very fragile.

There are quality control protocols that would catch the issue (most bladesmiths do a fairly rigorous bend test to determine the flexibility and strength of their blades), but if your smith is working past his capacity, those might fall by the wayside.

• The characteristic of clay that matters is its insulating ability. I don't see how you could change this enough to make a difference while still having something that could be called "clay".
– Mark
Jan 11 '19 at 0:18

Contaminate the ore they are using randomly over time in small batches (so that they can not refine their process) with chemicals which make the steel more brittle or hard, or chemically unstable:

• Phosphorus
• Sulfur
• Silicon

https://www.steeltank.com/Portals/0/Articles/Effect%20of%20Chemical%20Elements%20in%20Steel.pdf?ver=2009-05-31-010753-797

• It will be quite obvious during the forging process that the iron they're working with is defective.
– Mark
Jan 13 '19 at 23:04