In a certain world far beyond the reaches of our own, there are humans. Humans make war just like on Earth. They have an early modern level of technology- cannons, arquebuses, swords, axes, polearms, longbows, crossbows...and more.

They have one outlier. Steel Men, sets of power armor fashioned by skilled workers using rare crystals found underground. They have been made for over five hundred years. There are many things that go into the making of Steel Men. We won't go into them. There are five things to know.

  • Steel Men have two forms: the box form that can teleport to the wearer in need, and the armor form- where it splits into pieces from the box form and covers the wearer's body. Even in the armor form, they have gaps in the armor- around the neck and the joints. These gaps are vulnerable enough to allow an ordinary footsoldier to stab through them and into the undefended flesh of the wearer underneath (if they could get a hit off...)
  • Steel Men can fly and turn extremely fast, although they are sluggish while on the ground. How fast? Mach 3.. They increase the reflexes of their wearer to allow them to actually control them at this speed.
  • Steel Men are as durable as they need to be to survive colliding with each other at full speed (they weigh over 500 kilograms, with some weighing 800). Survive, not come out undamaged- which they will be, severely. They also limit the transmission of force to their wearers to make sure they don't get instantly turned into paste.
  • Steel Men only equip premade melee weapons as durable as them. Ranged weapons are slow and weak.
  • They are draining to use: the longer one wears them and the more intensive activity, the more it drains their energy. The longest anyone can last in them is two days, the shortest merely thirty minutes. When the limit is reached, the wearer goes unconscious.

Based on these five rules, how would a combat between two Steel Men users look like?

  • 2
    $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Worldbuilding Meta, or in Worldbuilding Chat. Comments continuing discussion may be removed. $\endgroup$
    – L.Dutch
    Nov 30, 2023 at 5:01
  • 1
    $\begingroup$ @NotIamNot Don't worry, I feel that way pretty much every time I ask a question here $\endgroup$
    – M S
    Nov 30, 2023 at 14:14
  • 3
    $\begingroup$ @Joachim You don't actually need to look at all how common they are; The question asks "only" for a duel between two of these steel men. $\endgroup$ Nov 30, 2023 at 17:02
  • 1
    $\begingroup$ @Demigan, If the opponents are the only thing in the sky, sure, but if they have a little maneuverability, they'd be able to use terrain (like in Independence day). If they have a lot of maneuverability, they'd be able to use buildings or forests. None of this would be able to block something that can withstand Mach 3, but there are plenty of opportunities to play hide and seek. $\endgroup$ Dec 1, 2023 at 19:12
  • 2
    $\begingroup$ "They also limit the transmission of force to their wearers to make sure they don't get instantly turned into paste" --- unfortunately this is simply impossible. Humans can't survive much more than 9 g's of acceleration, and that only for a few seconds. If you want to decelerate from mach 3 to 0 at 9 g it will take more than 11 seconds, which is likely to kill the wearer. But a collision is obviously going to take much less time than that, which means the acceleration will be much higher. No matter how much magical shock absorbers the suit has your humans are tomato puree. $\endgroup$
    – N. Virgo
    Dec 2, 2023 at 6:34

7 Answers 7


Frame Challenge

Okay - so - 2 of these Steel Men can survive an impact where they are both going at Mach 3.

A single Steel Man, massing 500 kg, travelling at Mach 3, has a whopping ~264 MJ of energy. 2 of them colliding will have 528 MJ of energy.

To put that into perspective, an M1 Abrams APFSDS round has a muzzle energy of 12 MJ. A 14 inch BL naval gun (the standard British battleship gun) - has a muzzle energy of 206 MJ.

TL;DR - if your armor can dissipate 528 MJ (even if that leaves you heavily injured) - there's not a standard melee weapon that is going to scratch this armor. Even assuming the melee weapon is as durable as you are - the speed at which it would need to be swung to inflict damage is silly:

A 7 kg weapon (double the weight of the largest 2 handed swords) - would need to be swung at 7,570 m/s or Mach 22 to come close (that's 200 MJ of energy there).

Bearing in mind a 'fast' sword swing is about 20 m/s.

So even if you have super speed strength and get it up to 20 times a normal "fast" swing - 400 m/s - you'd need a weapon that massed the same as a mid-sized SUV (2 tonnes) to get into the right ballpark.

Edit - Frame Challenge Part 2

So - I think I have found a 'cool' and somewhat believable way to make your idea work (as I said in my comment - flying Super Soldiers are cool).

I'm going to reference one of the coolest 1980s Jet Fighters - the F14 Tomcat. What does that have to do with medieval super soldiers?

Variable geometry wings - AKA swing wings. There's a setting for low-speed flight and a setting for low-drag, high speed flight (swept all the way back, looking cool AF).

Let's incorporate this idea: for your Steel Men to travel at top speed - aka Mach 3 - their suit has to be sealed and made rigid. This means they can't move their arms and legs whilst travelling at this speed and this extra rigidity something something magic armor something is what enables them to survive a Mach 3 impact.

However, in order to move their arms and legs, they can't have this sealed/rigid mode - this limits their speed (200-300 mph is plenty fast enough) and because of the need to move their arms and legs this is what necessitates the gaps in the armor. Now - depending on how quickly you can transition from high speed mode to low speed mode will dictate the combat.

If it's instant or near instant, you'd have a fighting style where one combatant would come in at full speed, then at the last possible second, slow-down, transition into fight mode, attempt to land a blow, then shoot off in full speed mode before the target can parry/counter etc.

If it's a few seconds in transition (which I think is the better version) - you'd still have an element of rush in and surprise, the target wouldn't have time to go to high-speed mode and evade, and you'd have a window of opportunity where both parties would attempt to get a decisive blow, then both would retreat off, try to gain some tactical advantage and then repeat.

It would kinda resemble a sort of fencing whereby they would come in, have a few blows then retreat - very quickly.. Except it would be in a 3D plane. You might even have a scenario where 2 skilled practitioners wouldn't opt to retreat - and you would have a hybrid of WW1/WW2 dog fighting maneuvers (think things like a vertical rolling scissors) whereby the goal is not to get on the tail of your opponent, but to position yourself to where you can target one of their weak spots.

I think this visually would look the coolest - but then I'm biased cause I like planes.

  • $\begingroup$ So to conclude your answer, the best way for these metal beasts to duel is to go bare-handed and charge at one another. $\endgroup$ Nov 30, 2023 at 0:29
  • 9
    $\begingroup$ @NotIamNot Gaps in their armor? At Mach 3? Nope. $\endgroup$
    – JBH
    Nov 30, 2023 at 0:32
  • 3
    $\begingroup$ @JBH We're not here to deny one explicitly stated world premise of the querent, regardless of whether they make sense with real-world. However... You can very easily frame-challenge two premises with one another, here the armor gaps and surviving the crash. $\endgroup$ Nov 30, 2023 at 0:38
  • 3
    $\begingroup$ For your second frame challenge, the incoming soldier would absolutely not transition to make a melee attack. They would just impact their non-sealed target, pulverizing them and creating a crater in the ground. $\endgroup$ Nov 30, 2023 at 15:01
  • 1
    $\begingroup$ @MichaelRichardson - good point - there's probably something else I could add here to eliminate that as an option (as it's just not interesting having Kamikaze knights) - but yeah - I did my best with the question :D $\endgroup$ Nov 30, 2023 at 19:01

Throw rocks at each other

You've got moderate impact resistance and weaknesses.

Your best defence is to always be moving fast enough that an opponent with a small light weapon can't get to the gaps in your armour. You could neutralise that defense to kill your target. This leads to one of your fighting styles, get in close and grapple with daggers. Always have a wingman to help prevent getting caught from behind and try to prevent your opponent from driving you into the side of a mountain while grappling.

They're sluggish on the ground, see if you can ground your opponent while staying airbourne yourself. You don't say anything about how they take off and being 2cm off the ground is still technically airbourne, so not a lot to work with here.

The most fun one to play with is the high speed impact damage

As has already been mentioned, there are massive energies at play. The first round or two of any fight is going to be about throwing rocks, big ones, small ones, pointy ones, cannon balls, whatever, it doesn't really matter for these purposes.

The trick is getting airbourne holding your object of choice, get some speed up, aim at your opponent, let go of said object and dodge away. You've effectively released a kinetic impactor at mach 3, even if you miss your target you're going to make a big mess of the castle/city/army behind it.

In conclusion:

You say they have cannons, but they won't use them. Steel men throwing rocks is more effective than any ordinary cannon, so the concept would never get significant development. As a technology they make a vast number of other early combat technologies redundant to the point where they'd never be developed. No city walls, or at least a vastly different concept of them, no artillery, minimal heavy cavalry. It's all redundant in the face of a steel man throwing rocks (or themselves).

You'll have to create an entire new concept of medieval combat and war around this technology.

  • $\begingroup$ Note that the querent asked only about steel men duels ^^. Still, you answered the question and it's very, very, very useful to understand that things would be very different overall if you apply better warfare strategy in this world. $\endgroup$ Nov 30, 2023 at 11:06
  • 5
    $\begingroup$ @Tortliena it's a standard problem, people want a classic medieval world with one extra feature, mythical beasts, dragons, magic etc and forget to allow for the fact it doesn't work like that. You can't have these things without making the entire world into something completely different, which means you can't meaningfully answer the question without a holistic viewpoint. $\endgroup$
    – Separatrix
    Nov 30, 2023 at 11:15

Throw tiny things

Let's skip the problems of the armour, like that smashing into each other at mach 3 will magically protect the wearer so they'll survive. You say it does, so it does.

The fact that the armour is so strong means that you can basically assume the armour is invincible. The only thing that will work is via the gaps in the armour. To do that, we have an easy solution. Throw gravel.

If you would put two people in medieval armour and throw gravel, you'll have an ok chance to hit the vital parts. It isn't a surefire way, but decent enough. The problem in normal combat is that you cannot throw hard enough for it to matter.

The armour however does not have this problem. With the capability to reach mach 3 and the reflections to react at those speeds means that you can throw gravel hard enough to wound.

Is this perfect? Hell no! With these speeds the distance between combatants can be much farther away at a moments notice. Avoiding a scatter, or being far enough away that they lose enough energy or scatter too much to reliably hit the exposed areas will be a problem. However, that is a problem of all weapons. With this technique you'll make sure to have the best possible chance.

Won't that be an epic ballad? Two grown men in high tech magical steel armour in an epic duel to the death, flying at high speeds through the air, throwing gravel at each other.

The ammunition supply lines will be grade A gravel/rocks towards the frontlines, together with men foraging for rocks as they go.

  • 2
    $\begingroup$ To tackle several standard infantry that way you'd need to take a rather uncomfortable angle of attack. Indeed, you would need -roughly- to move towards the ground at mach-3. Not impossible on plains, but highly inconvenient in mountains. Another solution is just to grab a big bag of bigger rocks and go in, lazy dog bombing style. If you can fly at mach-3, there would be not much issues flying at low speeds with an heavy payload. Just take into account that those rocks need to be a bit heavier due to a lack of good aerodynamics. $\endgroup$ Nov 30, 2023 at 13:52
  • $\begingroup$ @Tortliena good point. I somehow keep thinking these people go towards the ground for battle. I'll remove that part from the answer, as it's not answering the actual question anyway. $\endgroup$
    – Trioxidane
    Nov 30, 2023 at 16:32
  • $\begingroup$ @Tortliena mountains are not an issue - if we can hit another mach 3 metal man without issue, some rock shouldn't be an issue either. Soil would have a greater risk of getting you stuck. As for weaponry - get the largest bucket of rough gravel you can and carry it with you. Release while passing overhead. $\endgroup$ Dec 2, 2023 at 3:17
  • 1
    $\begingroup$ @DanielVestøl You should read back the question; Two steel men colliding at mach 3 is not done without issue. $\endgroup$ Dec 2, 2023 at 8:02

Aerial jousting.

They have long lances and fly straight at each other at high speed.

Spectacular, knightly, requires great courage and skill. Pennants and streamers for added visual effect, aim for the cracks in the other knight's armor and keep your nerve until that bone-jarring impact...every pass results in two broken lances, the knights re-arm and come at each other again...

  • Reflex speedup: a subjective flight speed of 10m/s would be quite fast with normal reflexes, especially in the vicinity of obstacles or other suits. This means that at Mach 3 (which equals about 1km/s), your reflexes would have to be 100 times as quick as normal! Many aspects of this simplify when you look at them from the point of view of the fast thinking suit wielders: everything looks more or less like they'd only fly at 10m/s. However, once they actually hit anything, they release 10000 times more energy!
  • One big factor will be how fast the suits are able to accelerate. In one extreme, their acceleration would be relatively 'slow', like falling from a plane without air resistance: Mach 3 equals about 1 km/s, so at ~10m/s² (normal gravitational acceleration) you'd take 100s, or almost 2 minutes, to reach full speed - and that time would feel significantly longer, given the improved reflexes. From the point of view of normal humans, this is already a very quick acceleration, and yet it's almost the lower limit if you realistically want to reach Mach 3.
    In the other extreme, suits could accelerate from 0 to Mach 3 basically instantly. If "instantly" still meant it took one second, this would mean an acceleration of 100G, which would already be lethal to unenhanced humans, but would still feel like 100s to the pilots. Acceleration from 0 to Mach 3 in one subjective second would imply 10kG, which should destroy melee weapons made from normal materials.

    If acceleration took subjective hours (at maximal reflex acceleration), the kinetics of combat would be very "positional", except that the "arena" could move around at insane velocities. Relative velocities during sustained combat would be relatively low, but it would be hard to dodge a full speed attack with a "spear" (discussion on weapons below).
    If acceleration was fast, your "position"/inertia wouldn't matter nearly as much, and it would all be about quick reactions/interactions - dodging or deflecting attacks, trying to hit your enemy in a weak spot, or simply confusing them with chaotic maneuvers.
  • Is flight Newtonian or "Aristotelian" (think Star Wars fighters)? In Newtonian combat, changing your direction gets harder the faster you are. If you can easily change your direction, "slowing down" by moving in zig-zag lines becomes a possibility, and combat is "simpler" in general (you don't need to care about your inertia vector, only your speed). Newtonian combat can be more "dangerous", in that a unwise maneuver might lead to combatants damaging themselves on mountains etc. they cant dodge in time.
  • Suit durability: As another answer already mentioned, surviving head-on collisions means the suits are pretty much invulnerable to anything except full speed collisions (which aren't even lethal). Offensively, suits can kill pretty much anything by "slowly" (maybe at Mach 1) flying through their target - at only about a tenth of their maximal impact energy, they shouldn't take much damage, yet would still hit like railgun projectiles. If these insane characteristics are not desired, maybe the suits could drastically reduce the inertial mass of their wearer - though that would complicate their function, since they'd still need a huge amount of propulsive power to overcome air resistance. This means the joints of the armor are the only vulnerability that matters (except for involuntary crashes, that release energy in the order of magnitude of 100 kg TNT).
  • Life support: when cruising at Mach 2, you have to deal with temperatures in excess of 100°C (the front of the Concorde reached 127°C at Mach 2). That means that even the seams/joints of the armor have to protect the occupant from heat. Not to mention that you wouldn't want to be breathing at Mach 3 even if you were heat resistant - you'd experience 11 bar of pressure from the direction of flight (close to sea level), and extreme turbulence on other sides. Or, when flying relatively high, there might not be enough air. So the armor effectively has to contain a fighter-grade life support system to be usable.
  • Weapons: Since the armor itself is mostly invulnerable, the obvious strategy is focusing on the "gaps" at the joints. To do this, I'd recommend a "metal toothbrush": many thin, long spikes at the end of a stick (ideally one that is longer than the opponents). The spikes hitting the armor will break off (or, if your material science permits, bend), while any that hit a joint will pierce the occupant (and bend/break on the inside, turning the occupant to mush). The propulsive power and/or inertia of the armor will easily penetrate any kind of under-armor protecting the joints, if an appropriate material is chosen for the weapon.
    The "pebble"-idea from another answer would also work quite well - though instead of pebbles, I'd use small metal or stone fragments you could throw at approaching opponents. The denser, the better - and reducing air resistance by making them bullet/arrow shaped would further increase the effective range. The important part is quantity though: you want to cover a large area with enough projectiles, that you can be sure a few will hit the joints of the target.
    If you wanted to try to break through the armor itself instead of attacking the joints, I see 2 options:
    a) really sharp lance: you hit an enemy with a long spike that is fixed to your armor, has a relatively large base and a very narrow point. This means the kinetic energy/inertia is highly concentrated on the opponents armor, while on your armor the force is distributed over a large area (and therefore less dangerous). Making the lance relatively heavy further shifts crash damage from the attacker to the target.
    b) a really heavy mass: you effectively let the opponent collide with a suits worth of metal, that isn't attached to yourself. This means you shouldn't take any damage at all with correct usage, but would have to lift a 500kg object with you. A major problem with both of these is that they depend on high relative speeds - eg. a charge at a stationary target. If the opponent is able to match its speed to yours, you likely wont be able to release enough energy to even scratch their armor. So "hedgehog halberds" will be the most dangerous melee weapon against suits, with ranged "knife storm" attacks being excellent opening salvos.

Let's start with why are they fighting and work from there.

In order for these IronSteel Men to be important in combat they have to be effective against other troops. It's powered armor, so it's almost certain that they're going to be stronger than the average. They may not be much faster, but it takes a very skilled swordsman (or spearman, or whatever) to actually get through the armor to kill the pilot. Meanwhile the pilot is devastating due to sheer strength.

In the air a pilot can do fly-bys at supersonic speed, with the resultant turbulence causing direct damage to ground troops if they're low enough (don't do this though, because nets suck) or simply by dropping bundles of short spears at Mach 3 over enemy formations.

So what are my objectives as a pilot in one of these engagements?

First I need to keep the enemy pilot busy so that my ground forces have a chance to do their thing. If taking them out is an option then that's good, but the suits are stupidly robust so that's going to be difficult. Mostly I just need to keep them away from my guys, and they need to keep me away from theirs.

Gound Combat

Let's get this one out of the way quickly. Once you're on the ground the objective is to force the other suit to engage one-on-one with you. Your respective ground forces will assist as and when opportunity arises, but you must prevent the other suit from rampaging through the weaker forces.

This is going to end up as a bit of a brawl, with the win probably going to whoever has the best agility in the suits. Power strikes and grappling are the main features to expect and train for, with a focus on crippling the other pilot to ensure they can't continue to fight. Ripping one of their limbs off will probably do the trick. But even just holding them down while friendly ground units try to breach the suit is viable.

Entanglement weapons are particularly useful in this scenario. Steel bolas, nets and ropes to entangle the suit will force the pilot to expend extra energy to break free, reducing their remaining operational time.

Air Combat

Here the objective is simply to keep pressure on the opponent to keep them away from your ground forces until they run down their energy and leave the field. You might get lucky and force a grounding, but an experienced pilot isn't going to be handing you that opportunity for nothing.

Considering the durability of the suits, the most likely mid-air tactic is going to be equivalent to shoulder-barging. It's going to be a flying demolition derby between two virtually indestructable contestants, bashing into each other and probably grappling in mid-air. Without ground leverage the grappling probably isn't going to result in much more than a lot of noise and changes in direction. The 'defender' is going to try to drag the 'attacker' down to the ground where they can be trapped amongst a prepared ground force with nets and spears, while the attacker is going to be trying to avoid exactly that happening.

When all else fails, break towards the enemy force. He's just as invested in stopping you from harassing his ground troops as you are towards him. Throw out some collateral damage to his troops and he's going to have to do something about it. Feinting towards his troops will keep him interested... unless he's fine with mutual annihilation.

Mostly though this is going to look like a couple of guys in suits going hand-to-hand in mid air. Slow-motion Saiyen fight without the power attacks, just lots of bashing into each other and throwing each other around. Probably look really cool, but who has time to watch when you're being quick-marched into battle?


The simplest win condition is to field more suits than your enemy. If they have two you field three. If you turn up with three and they actually have four, get the hell out of there. Because each suit that isn't being tied up is going to be wreaking havoc on the ground.

Second is stamina. If your opponent has less flight capacity than you, you just have to wear them down until you get that numbers advantage. In the sky, on the ground, just beat them down until one side has the numbers to win. Once one of them falls you have freed up a pilot to go kill the ground troops. And if you do it through exhaustion, peel the pilot out of his suit and give it to someone else on your side. Instant domination!

Third, tactics and pure combat ability. The least important here due to the overwhelming dominance of numbers in the win/lose equation, but still important. Train your pilots in every form of entanglement weapon, both using and facing. Run them through endless grappling scenarios. Have them practice grappling and entanglement every single day against each other. Build better entanglement weapons: bolas are great, nets are classic, Kusarigama are freaking amazing when used well.

And the final winning strategy: black ops. Find out who the pilots are and kill them in their sleep. Poison their food. Hold their families hostage. Anything it takes to keep them off the field in the first place. Whatever you have to do, no matter how despicable, to get the numbers advantage. And if you can steal their armor and use it for yourself, all the better. Whatever. It. Takes.


NotIamNot, welcome. It would be similar to how plate-armored knights fought each other. They too had armor that could withstand most weapons of the time, but had gaps and weak points which could have been defeated more easily. So for Steel Men, think a fencing match at extreme fast forward. If you are interested in specific maneuvres, there are some combat manuals from the period which survive to this day, or you can consult your local HEMA group.

  • 2
    $\begingroup$ Be careful with old time manuals, the fact you have a much faster speed but still about the same range and you are fighting in a 3d space change a lot of things ^^. I remember Shadiversity making a point when duelling in space (and so in 3d), might be worth a look to understand some specifics : here $\endgroup$ Nov 30, 2023 at 1:04
  • $\begingroup$ @Tortliena, thank you. But does it really? As per the OP's description, the armor suit boosts the wearer's reflexes and maneuvrability to match the increased speed; and fencing always takes place in a 3D space. Despite all the new angles and dynamics, the presence of heavy armor ensures that the overall strategy of "strike a weak spot in the armor" remains the same too. $\endgroup$
    – ihaveideas
    Nov 30, 2023 at 9:17
  • $\begingroup$ While the goal doesn't change, the way of achieving it does. Here are three examples : First, I'll always try to be lower than you, relative to your body, so I can hit your legs and waist while you'll be in an awkward position, all bended over. Then, if one rotates 90° to the right or left and is horizontal, you'll need to adapt and defend differently, since all angles of attacks will be also turned by 90°. If you turn upside-down, you'll even have to fight an opponent mainly targetting your legs now ^^. Their attacks will also flip to the left for right-handed duellists (right for lefties). $\endgroup$ Nov 30, 2023 at 10:13
  • $\begingroup$ Let's note above that I restricted myself to 3d positionning only, with fighters with about the same kind of mobility on land... Just in air. With virtually no friction to "stand your ground" , you'll be pushed back at every parried hit, so you'll either have to thrust yourself back forward or actually fully accept it to get some breath. Footwork matters much less in the air. Let's add that you can accelerate your offensives for much longer (your speed can vary a lot more) and you get the gist ^^. $\endgroup$ Nov 30, 2023 at 10:35
  • $\begingroup$ Magnetic or Welded attachement, to bring full force to bear. $\endgroup$
    – Pica
    Nov 30, 2023 at 16:05

You must log in to answer this question.