Scadrial vs. Roshar post Lost metal.

[Frustration]

Alright, given everything we've learned in LM, if Roshar and Scadrial we're to fight who would win?

For the purposes of this thread we will be assuming that each side only gets their native powers and people. So Scadrial doesn't get the Ghostbloods, Roshar doesn't get Nightblood.

Shards and Dawnshards will not be considered.

Edited November 17, 2022 by Frustration

[Karger]

Sadly this duty falls to us.

It still depends on the rules of engagement.  The invaded side seems like it will usually have the advantage just because of how difficult it is too move large numbers of people through the CR. 

Both sides have WMDs now.

Roshar's knights are more powerful in combat but far less efficient.  Roshar has also had far more wars and thus understands warfare much better. 

Scadrials scientific and commercial arts are more developed.  Additionally they have a better bureaucracy.

[kenod]

Roshar likely has better shock troops and high-level combatants, as well as better access to battlefield support magic, though if Scandrial goes ham on the hemalurgy they can probably get some pretty decent combatants too, though I'm not sure how viable it is, since you're also reducing your total number, unless you're just grabbing support powers not very useful on their own, like Duralumin.

Scandrial has better tech though, right now, especially militarily speaking. And, if the South joins in, I suspect they also have a more potent airforce, or at least a more diverse one, which isn't just focused on dogfighting. And, to be honest, top-level combatants like Shardbearers, Radiants, Mistings and Ferrings are rare enough that regular military force is likely still more important, and here Scandrial's access to firearms will likely allow them to beat Roshar, though only if they can deploy them effectively.

Population levels could be an issue though, Scandrial's populations (or at least inhabited territory) still feels somewhat small compared to Roshar, but I'm not sure to which degree urbanization makes a difference here.

That said, one very big issue is that, as stated in the beginning of LM, the North's military forces, aside from smaller peacekeeping forces, are still very new, with no real previous engagements. This means that their military likely still has a lot of issues owing to lack of experience. It also wouldn't surprise me if their logistical base, while strong on Scandrial itself, isn't well-suited for offensive deployments, while Roshar's is quite experienced in that.

Personally I'd say that if Scandrial pulls themselves together fast enough to gain the necessary military experience and make adjustments to their plans and doctrines, they can probably win, while if they take too long, even if they can hold defensively, Roshar will eventually develop their own versions of firearms and other heavier weapons, at which point their superior numbers, shock troopers, and experience, will allow them to conquer Scandrial.

Edited November 15, 2022 by kenod

[Knight Oblivion]

I still argue that from a physiological standpoint it would be difficult for Roshar to project power outside of itself. It's gravitational field is below the Cosmere norm and their atmosphere is more oxygen rich. Both of which will give non-Radiant Rosharans (especially if they're not Windrunners) a severe disadvantage both cardiovascularly and activity-wise. 

 

Everything will be harder for them if they try to go to a planet like Scadrial. Everything. Meanwhile, a normal Scadrian on Roshar would be almost like Captain America, stronger and able to last longer when it comes to physical exertion.

[StanLemon]

In terms of conventional military power? Scadrial would destroy Roshar. There is a reason Hoid mentioned to Jasnah how infantry doesn't last against more modern weaponry.

In terms of Invested military power? Roshar in several ways has the edge do to the higher raw power, though without a Bondsmith to empower the Radiants they would run out of Stormlight relatively quickly so they would be most useful in assaults meant to destroy Scadrian military infrastructure.

I think whoever is the aggressor would be the one at a major disadvantage and most likely would lose. 

[Wadders]

I am not sure how well shardplate would hold up against semi-automatic rifle fire.

In additon people with weight medallions shooting the heavy guns that wax has been using would be pretty devastating.

[Kasimir]

4 hours ago, Karger said:

Scadrials scientific and commercial arts are more developed.  Additionally they have a better bureaucracy.

Would not underestimate the importance of logistics.

To be fair, Roshar can't be awful at it, given the number of wars they'd've fought in, but that being said, feels like Soulcasters etcetera have given them an edge in not having to worry as much about supply lines. Not sure this functions as well for them if waging a war of aggression (defense is probably a different story.)

Edited November 15, 2022 by Kasimir

[Karger]

27 minutes ago, Wadders said:

I am not sure how well shardplate would hold up against semi-automatic rifle fire.

Pretty well actually.  I believe we have a WoB about it.  The stuff is durable.  Godmetals may tend that way given bavadium

28 minutes ago, Wadders said:

In additon people with weight medallions shooting the heavy guns that wax has been using would be pretty devastating.

If you could get enough of them.  Growls at Brandon.  You still haven't explained them yet!

[Wadders]

Considering everyone on an airship crew would need a medallion and their airships don't seem that rare in southern scadrial. My guess is that the limit is more to do with the number of metalborn available to create them. In the event of an interplanetary war I think they might be more willing to work with the northerners.

Also it occurs to me that they have cannons, artillary and are not far off rocketry which the Rosharans don't really have an effective means to counter.

Edited November 15, 2022 by Wadders

[NameIess]

Something to remember is that as long as the timeline doesn't get shifted, Roshar in SA 4 is still ~10-20 years behind Scadrial, so they'll have that much time to catch up technologically. Considering how quickly they've advanced in the books (a period less than half of the most conservative estimate) I wouldn't count on Scadrial having a absolutely overwhelming technological advantage. Fabrial science went from floating platforms to Bridge 4 in about a year, and that was before getting access to the Sibling or having an easy way to transfer investiture between gemstones.

All in all, I think an invasion would be a loss for whoever initiated it. Roshar would be better at it because of Elsecallers and Bondsmiths (assuming they figure out offworld Radiants of course), so long as they had time to spy out essential targets beforehand without Harmony interfering, but they'd still lose. North Scadrial knows basically nothing about war and less about Shadesmar, so they'd have an incredibly hard time getting any substantial force to Roshar, and they'd still have to deal with the chokepoint of the perpendicularities.

[+robardin]

Well as we know it as of now (TLM and SA4), the Metallic Arts are FAR more portable than Surgebinding... Neither Stormlight nor people with Nahel Bonds can be taken off of Roshar (yet).

So yeah, if Scadrians landed on Roshar, the Radiants have home field advantage for sure, but I can't see an army of 3+ Ideal Radiants finding their way onto Scadrial.

[snowbreaker]

19 hours ago, robardin said:

Well as we know it as of now (TLM and SA4), the Metallic Arts are FAR more portable than Surgebinding... Neither Stormlight nor people with Nahel Bonds can be taken off of Roshar (yet).

So yeah, if Scadrians landed on Roshar, the Radiants have home field advantage for sure, but I can't see an army of 3+ Ideal Radiants finding their way onto Scadrial.

IDK seems implied in chapter 70 that some skybreakers are on Scadrial - the 8 'allomancers' that fly away to sink the ships after checking the legality of it with the governor. So I'm team Roshar here. 

[+robardin]

3 minutes ago, snowbreaker said:

IDK seems implied in chapter 70 that some skybreakers are on Scadrial - the 8 'allomancers' that fly away to sink the ships after checking the legality of it with the governor. So I'm team Roshar here. 

Why would you think they were anything other than Coinshots? Certainly Steris didn’t think anything odd about them flying off, like “huh, I didn’t see them drop any coins” (not that they’d need to, anyway, in a city like Elendel that’s full of metal achors at many heights).

[TheOneKEA]

5 minutes ago, snowbreaker said:

IDK seems implied in chapter 70 that some skybreakers are on Scadrial - the 8 'allomancers' that fly away to sink the ships after checking the legality of it with the governor. So I'm team Roshar here. 

Good catch! That seems very significant.

[snowbreaker]

1 minute ago, robardin said:

Why would you think they were anything other than Coinshots? Certainly Steris didn’t think anything odd about them flying off, like “huh, I didn’t see them drop any coins” (not that they’d need to, anyway, in a city like Elendel that’s full of metal achors at many heights).

They could be but seems a bit more significant to me. First, they are Ghostblood agents. Then, the dialogue around legality - "You are certain this is legal? The mass sinking of private ships?"

Steris dismisses them because, well, why wouldn't she. But we know better.

[CaptainRyan]

16 hours ago, snowbreaker said:

They could be but seems a bit more significant to me. First, they are Ghostblood agents. Then, the dialogue around legality - "You are certain this is legal? The mass sinking of private ships?"

Steris dismisses them because, well, why wouldn't she. But we know better.

This seems like a huge stretch to me. 

We know Kelsier is still trapped on Scadrial at this point. If the Ghostbloods know how to get a Nahel bond off Roshar, then Kelsier would almost certainly know how to leave Scadrial. 

At best, this is Brandon deliberately tweaking people's noses for fun. At worst, this is an example of how this community sometimes reads a bit too much into things.

(All my opinion of course, happy to be proven wrong.)

[snowbreaker]

11 minutes ago, CaptainRyan said:

At best, this is Brandon deliberately tweaking people's noses for fun. At worst, this is an example of how this community sometimes reads a bit too much into things.

It could be a nose tweak, but I'd be shocked if it's just a random coincidence. A lot of things previously thought to be extremely difficult/almost impossible are happening, and I think some sort of Rosharan exodus is being hinted at, so I wouldn't be surprised if they are Skybreakers. 

[kenod]

17 minutes ago, CaptainRyan said:

This seems like a huge stretch to me. 

We know Kelsier is still trapped on Scadrial at this point. If the Ghostbloods know how to get a Nahel bond off Roshar, then Kelsier would almost certainly know how to leave Scadrial. 

At best, this is Brandon deliberately tweaking people's noses for fun. At worst, this is an example of how this community sometimes reads a bit too much into things.

(All my opinion of course, happy to be proven wrong.)

One big thing we should look for is how they destroyed them. I can't really remember myself, but aside from the flight, destroying boats with steelpushing would look very different from Gravitation or Division.

[Karger]

33 minutes ago, kenod said:

One big thing we should look for is how they destroyed them. I can't really remember myself, but aside from the flight, destroying boats with steelpushing would look very different from Gravitation or Division.

They also didn't glow nor were they particularly tall nor did the speak in an odd manner.  I think they just wanted to avoid run ins with law enforcement later.

[Chaos]

@robardin You need to spoiler tag any Secret Project information at all, as many are trying to avoid it.

[Frustration]

On 11/15/2022 at 3:33 PM, Wadders said:

I am not sure how well shardplate would hold up against semi-automatic rifle fire.

Incredibly well.

On 11/15/2022 at 5:13 PM, robardin said:

Well as we know it as of now (TLM and SA4), the Metallic Arts are FAR more portable than Surgebinding... Neither Stormlight nor people with Nahel Bonds can be taken off of Roshar (yet).

Mraize said that it was just a connection issue(RoW 188), any Bondsmith should be able to make it work.

 

I've been preparing for this for a long time, and have participating in similar discussions in the past. And I have been severely underestimating Roshar.

I'll break this up into multiple parts

1. Roshar is impossible to invade.

Spoiler

The first problem is the spren. Not radiant spren, emotion spren. In particular angerspren. Angerspren are noted as dangerous(OB 887), enough that even Nahel spren fear them. Try marching an army of sufficient size to be a threat through the CR without drawing a host of these.

The second problem an invading force would have to deal with is perpendicularities. There are over thirty of them on Roshar, all of them controlled by natives. The Oathgates will only work for a Radiant so those are unusable for invaders, while the others are in the horneater peaks, which are cold enough to kill south Scadrial's without them tapping far too much heat to be sustainable. On top of that the peaks are difficult to transverse and far from any targets of importance.

The third problem is the storms. The Highstorm and Everstorm come consistently, and would completely destroy and airships they managed to build (because the perpendicularities are too small to bring them with). And the rain would set off any Harmonium they had, while also likely ruining their gunpowder, and possibly killing most of their forces.

The fourth problem is the oxygen. Now with lower gravity and higher oxygen the Scadrial forces would be feeling pretty good physically. But it would also cause them a lot of problems. Khriss warns worldhoppers about fire, anything from cookfires to guns become a lot more dangerous on Roshar than what the scadrians would be used to. I expect it will take several accidents, and likely several deaths before they fully realize this. Firearms may even prove deadly to the person using them.

The fifth problem is the natives. Yeah, Rosharan resistance is number 5. Rosharans are tall and strong. Kaladin would be 7 feet by our standards and to Roshar that's only 6'4. (https://wob.coppermind.net/events/374/#e12138 + https://wob.coppermind.net/events/7/#e7144). Rock and Eshonai are both 7 feet tall to Rosharans, so we're looking at 7'6 - 7-10. Rosharans are massive and incredibly strong. Not to mention warforms and regals being even stronger.

The Sixth problem is surgebinders. Weapons that can sever the soul, armor that resists bullets(https://wob.coppermind.net/events/100/#e3561). Healing, flight, teleportation, lasers, infinite stormlight etc. No scadrians magic can outperform surgebinding. Mistborn, Feruchemist, compounding, it doesn't matter, none of them can beat 4th oath Radiants with any level of reliability.

The seventh problem is fabrials. Painrails, soulcasters, regrowth fabrials, Shields, suppression etc.

2. Scadrial can be invaded quite easily.

Spoiler

Scadrial has only one perpendicularity, but with Bondsmiths and Elsecallers that isn't a problem. Roshar could even move an Oathgate to Scadrial, which would spell the end for any resistance, as Roshar could simply resupply too quickly.

Once their Scadrial has little in the way of barriers to stop invasion. The basin is too open, and its rail lines too easily severed. A single oath 3 skybreaker could eliminate all railways in a week. From there Scadrial couldn't do more than put up token resistance and sue for peace.

The thing is Roshar has too many advantages. Their magic is superior, their mobility superior, their fabrials superior, their population is higher. The only thing Scadrial has going for it is a slight edge in conventional technology, but Roshar's fabrials are quickly eating up that difference.

Edited November 17, 2022 by Frustration

[NameIess]

4 hours ago, Frustration said:

1. Roshar is impossible to invade.

  Reveal hidden contents

I agree, although I don’t think guns would be overly affected by the increased oxygen. The biggest problem is the chokepoints in the perpendicularities, and the travel through Shadesmar itself.

Quote

2. Scadrial can be invaded quite easily.

I disagree on this point. Scadrial has the Ghostbloods, who hold the capability to wreak havoc on the supply lines and leadership of Scadrial. Additionally, there’s the Kandra, who will be able to conduct excellent recon and further sabotage.

Roshar may be able to make perpendicularities, but they currently only have one person capable of doing mass transit and resupplying Stormlight on Scadrial. Elsecallers are able to get themselves over, maybe even small groups, but that’s the extent of it. They certainly won’t be getting any Bridge 4’s onto Scadrial. Also, there’s the question of whether or not Bondsmiths can even leave Roshar. Considering how important the Stormfather is to the planet, it might not be safe to disconnect him enough to allow worldhopping. Could end up in a similar situation with Ba-Ado-Mishram, probably even worse.

As for Scadrial’s defenses against an invasion, they have the Bands, as long as they can recharge them, a whole bunch of metalborn, even some potential Mistborn with Wax’s Lerasium dose, and of course Marsh. Marsh is a full compounder with centuries of experience, practically a second Lord Ruler. Any potential invasion will have to go through him. Additionally, they have plenty of airships, easy access to aluminum, firearms, high explosives, rockets, mortars, and warships. Radiants might be basically unkillable with enough Stormlight, but regular soldiers are not. And as we all know, Shardbearers can’t hold ground.

looking at the regular soldiers, there’s even more of a problem: the increased gravity and decreased oxygen levels. Radiants can shrug that off, but regular soldiers will have a very hard time adjusting. I doubt they’ll be in fighting shape for quite some time after they arrive. Beyond that, they tend to wear metal, and use metal weapons, both of which will make them extremely vulnerable to steelpushes. And of course there’s the tech disadvantage, with Scadrial’s guns, grenade launchers, and soon to be rockets ripping apart any organized force that tries to invade. Which means no big armies, which means no full-scale invasions.

TLDR:

full-scale invasion of Scadrial: basically impossible.

Conducting interplanetary terrorism on Scadrial: Super easy, barely an inconvenience!

[Frustration]

1 hour ago, Nameless said:

Conducting interplanetary terrorism on Scadrial: Super easy, barely an inconvenience!

I'm just imagining a skybreaker going full division flying through some skyscrapers in Scadrial 9/11 right now, thank you sir.

1 hour ago, Nameless said:

I disagree on this point. Scadrial has the Ghostbloods, who hold the capability to wreak havoc on the supply lines and leadership of Scadrial. Additionally, there’s the Kandra, who will be able to conduct excellent recon and further sabotage.

So, I'd say the only ghostbloods allowed are scasrian natives. And Kandra cannot mimic Radiants, or singers, and any Elsecaller, Lightweaver, or Willshaper can see what they are by looking into the CR.

1 hour ago, Nameless said:

Roshar may be able to make perpendicularities, but they currently only have one person capable of doing mass transit and resupplying Stormlight on Scadrial. Elsecallers are able to get themselves over, maybe even small groups, but that’s the extent of it. They certainly won’t be getting any Bridge 4’s onto Scadrial. Also, there’s the question of whether or not Bondsmiths can even leave Roshar. Considering how important the Stormfather is to the planet, it might not be safe to disconnect him enough to allow worldhopping. Could end up in a similar situation with Ba-Ado-Mishram, probably even worse.

Actually it would be fine.

Spoiler

Questioner

Does the spren have to be present for a Surgebinder to have their abilities? Because with Dalinar, the Stormfather won’t be around all the time...

Brandon Sanderson

Good Question! Fortunately, the Stormfather is a little more omnipresent. Normally you’re gonna have to have your spren close, but the Stormfather absorbed... is basically Honor’s Cognitive Shadow, which means he’s got a connection to a lot of different things, so he’s not bound by a lot of the rules that others are.

Shadows of Self San Francisco signing (Oct. 9, 2015)

Additionally they can use Tai-na gemhearts to store stormlight, or use cohesion to make larger perfect gemstones.

1 hour ago, Nameless said:

As for Scadrial’s defenses against an invasion, they have the Bands, as long as they can recharge them,

Let's assume this works(which I believe it will) that's one person, and only so many attributes. Have Elsecallers soulcast an aluminum box around him, harry them with Windrunners, atrack with Lightweavers, jusr wear them down. They'll run out of attributes eventually.

1 hour ago, Nameless said:

a whole bunch of metalborn, even some potential Mistborn with Wax’s Lerasium dose

The lerasium only appeared once, and hasn't been able to be replicated. And Wayne ate all of it.

1 hour ago, Nameless said:

Marsh is a full compounder with centuries of experience, practically a second Lord Ruler. Any potential invasion will have to go through him.

Inqusitors have to rest a lot and it gets worse as they get older. I doubt Marsh can manage more than a few active hours a week. Additionally he isn't fullborn, he only has 21 spikes, 2 are for Atium, and there are probably multiple a-steel ones.

1 hour ago, Nameless said:

Additionally, they have plenty of airships,

Scadrian airships make about 25 mph, and can be brought down by a single squire.

1 hour ago, Nameless said:

Beyond that, they tend to wear metal, and use metal weapons, both of which will make them extremely vulnerable to steelpushes.

A rosharan will be heavier than their scadrian counterpart.

1 hour ago, Nameless said:

And of course there’s the tech disadvantage, with Scadrial’s guns, grenade launchers, and soon to be rockets ripping apart any organized force that tries to invade. Which means no big armies, which means no full-scale invasions.

Sibling sheild generators should do the trick. 

[TheTuninator]

6 hours ago, Frustration said:

Incredibly well.

Mraize said that it was just a connection issue(RoW 188), any Bondsmith should be able to make it work.

 

I've been preparing for this for a long time, and have participating in similar discussions in the past. And I have been severely underestimating Roshar.

I'll break this up into multiple parts

1. Roshar is impossible to invade.

  Reveal hidden contents

The first problem is the spren. Not radiant spren, emotion spren. In particular angerspren. Angerspren are noted as dangerous(OB 887), enough that even Nahel spren fear them. Try marching an army of sufficient size to be a threat through the CR without drawing a host of these.

The second problem an invading force would have to deal with is perpendicularities. There are over thirty of them on Roshar, all of them controlled by natives. The Oathgates will only work for a Radiant so those are unusable for invaders, while the others are in the horneater peaks, which are cold enough to kill south Scadrial's without them tapping far too much heat to be sustainable. On top of that the peaks are difficult to transverse and far from any targets of importance.

The third problem is the storms. The Highstorm and Everstorm come consistently, and would completely destroy and airships they managed to build (because the perpendicularities are too small to bring them with). And the rain would set off any Harmonium they had, while also likely ruining their gunpowder, and possibly killing most of their forces.

The fourth problem is the oxygen. Now with lower gravity and higher oxygen the Scadrial forces would be feeling pretty good physically. But it would also cause them a lot of problems. Khriss warns worldhoppers about fire, anything from cookfires to guns become a lot more dangerous on Roshar than what the scadrians would be used to. I expect it will take several accidents, and likely several deaths before they fully realize this. Firearms may even prove deadly to the person using them.

The fifth problem is the natives. Yeah, Rosharan resistance is number 5. Rosharans are tall and strong. Kaladin would be 7 feet by our standards and to Roshar that's only 6'4. (https://wob.coppermind.net/events/374/#e12138 + https://wob.coppermind.net/events/7/#e7144). Rock and Eshonai are both 7 feet tall to Rosharans, so we're looking at 7'6 - 7-10. Rosharans are massive and incredibly strong. Not to mention warforms and regals being even stronger.

The Sixth problem is surgebinders. Weapons that can sever the soul, armor that resists bullets(https://wob.coppermind.net/events/100/#e3561). Healing, flight, teleportation, lasers, infinite stormlight etc. No scadrians magic can outperform surgebinding. Mistborn, Feruchemist, compounding, it doesn't matter, none of them can beat 4th oath Radiants with any level of reliability.

The seventh problem is fabrials. Painrails, soulcasters, regrowth fabrials, Shields, suppression etc.

2. Scadrial can be invaded quite easily.

  Reveal hidden contents

Scadrial has only one perpendicularity, but with Bondsmiths and Elsecallers that isn't a problem. Roshar could even move an Oathgate to Scadrial, which would spell the end for any resistance, as Roshar could simply resupply too quickly.

Once their Scadrial has little in the way of barriers to stop invasion. The basin is too open, and its rail lines too easily severed. A single oath 3 skybreaker could eliminate all railways in a week. From there Scadrial couldn't do more than put up token resistance and sue for peace.

The thing is Roshar has too many advantages. Their magic is superior, their mobility superior, their fabrials superior, their population is higher. The only thing Scadrial has going for it is a slight edge in conventional technology, but Roshar's fabrials are quickly eating up that difference.

It's worth keeping in mind that while Sazed may not be able to do much directly (so far), having an active Shard holder in your corner is still a pretty big deal.

Anyways, since the more narratively interesting result is "they are more or less evenly matched", I suspect that's what the answer would be.

[NameIess]

1 minute ago, Frustration said:

So, I'd say the only ghostbloods allowed are scasrian natives. And Kandra cannot mimic Radiants, or singers, and any Elsecaller, Lightweaver, or Willshaper can see what they are by looking into the CR.

Considering how far Shai was willing to go to stop the invasion, I'd say that all the Ghostbloods are willing. Protecting Scadrial is literally their first tenet.

2 minutes ago, Frustration said:

Actually it would be fine.

  Reveal hidden contents

Questioner

Does the spren have to be present for a Surgebinder to have their abilities? Because with Dalinar, the Stormfather won’t be around all the time...

Brandon Sanderson

Good Question! Fortunately, the Stormfather is a little more omnipresent. Normally you’re gonna have to have your spren close, but the Stormfather absorbed... is basically Honor’s Cognitive Shadow, which means he’s got a connection to a lot of different things, so he’s not bound by a lot of the rules that others are.

Shadows of Self San Francisco signing (Oct. 9, 2015)

 

The Bondsmith would still be stuck on Roshar unless the Stormfather was unbound from it or his own bond were broken.

7 minutes ago, Frustration said:

Additionally they can use Tai-na gemhearts to store stormlight, or use cohesion to make larger perfect gemstones.

Very limited, in terms of a months-to-years long war. And supply chains will be difficult to upkeep.

8 minutes ago, Frustration said:

The lerasium only appeared once, and hasn't been able to be replicated. And Wayne ate all of it.

Well, it almost certainly did appear more than once, but Harmony probably won't be sharing any of it. In any case, I was more referring to Wax's descendants, as he's a full Mistborn now, if a weak one.

9 minutes ago, Frustration said:

Inqusitors have to rest a lot and it gets worse as they get older. I doubt Marsh can manage more than a few active hours a week. Additionally he isn't fullborn, he only has 21 spikes, 2 are for Atium, and there are probably multiple a-steel ones.

He's practically a Fullborn, in that he has steel and gold compounding. And with the Atium he's gotten, he'll be able to stay plenty active. Not like he'd need more than a few hours to destroy an army anyways.

10 minutes ago, Frustration said:

Scadrian airships make about 25 mph, and can be brought down by a single squire.

Not when they're staffed with Metalborn armed with aluminum they can't. And squires can't fly without Stormlight which, as previously mentioned, is rather hard to come by on Scadrial, even with perfect gemstones.

12 minutes ago, Frustration said:

Sibling sheild generators should do the trick. 

We don't know how those shields work, and they seem to require external gemstones which would be vulnerable to shelling. Besides, even if Roshar can get a footing, hunkering behind shields just gives Scadrial more time to aim the antimatter bombs.