If Horus could have chosen the legions that sided with him..

[GhostMalone]

Hmmm see that's when they're in euphoria they are still aware it's been stated before its more like an auto pilot. If they have set strategies they can still undertake them. That was a full on smash them into the ground situation.

 

If angron and his sons can pull of heavy mechanised sieges I think they can have enough restraint if pre ordained

[Gree]

Hmmm see that's when they're in euphoria they are still aware it's been stated before its more like an auto pilot. If they have set strategies they can still undertake them. That was a full on smash them into the ground situation.

 

If angron and his sons can pull of heavy mechanised sieges I think they can have enough restraint if pre ordained

 

Again, Betrayer does not really describe what you state. It shows the World Eaters being robbed of reason and sanity.. At one point Khârn tries to call out for support and he realizes that nobody is responding because they are too badly berserking and they can't even understand his orders. The Ultramarines take pretty big advantage of this, luring the World Eaters into ambushes and traps were they are simply too insane to avoid.

 

Maybe the World Eaters were relatively coherent earlier on in the Great Crusade, but by the time of Betrayer they seem to have degenerated more and more. Angron in fact was noted to actually get worse in his madness as time went on.

[Kol Saresk]

 

 

Then why did the Ultramarines not easily beat the World eaters ?

.....because they where heavily outnumbered by the combined forces of the World Eaters and Word Bearers? I already stated that. Even then the Ultramarines were noted to have inflicted heavy losses on the World Eaters, heavier losses then WE should have taken against a force that size. ( I assume you are referring to Betrayer)

 

 

Actually, they weren't. One of the problems mentioned in Betrayer in relation to the battle of Armatura was that the force that was there, would not be able to take the defenses because the defenses were that superior. But two king-ships later, the orbital blockade was broken. From there, the World Eaters were constantly throwing themselves at the defenders while the Word Bearers held back and "consecrated" the grounds. It wasn't until Lorgar joined in that the Word Bearers actually started fighting. And yet, Armatura fell.

 

At Nurceria, there were only a few thousand Traitor Marines present with a total of three ships. But when the Ultramarines showed up, it was with dozens of ships, the least of which had a carrying capacity of a thousand Ultramarines and at least one Dominus-class battle barge which carried three thousand Astartes. One Dominus and two standard battle barges have the troop capacity to land five thousand Astartes where only 600 World Eaters(the Eight Company and the Triarii who numbered 500, or five companies) plus the Word Bearer forces. Although the Triarii remained in orbit and defended the Conqueror against boarders like they were supposed to. And somehow they didn't kill members of their own crew while they were in the midst of the Nails.

 

But ultimately, due to the Ultramarines coming in waves and the Fidelitas Lex and the Conqueror only being classed as secondary targets while the fleet divided itself between attacking the Trisagion and landing troops, the Ultramarines fleet would suffer devastating losses.

 

Ironically, the Ultramarines were beaten both times not through superior numbers, but by superior tactics. The first being two highly maneuverable, starfort-equivalent ships destroying the orbital defenses along with two fleets of unknown strength, and then two battle barges and a king-ship severely hampering the efforts to land troops. When the Ultramarines left, one battle-barge would be destroyed, another severely crippled. No idea on the losses suffered by the Word Bearers and World Eaters.

[Gree]

Actually, they weren't.

 

Do you have any source stating that the Ultramarines were not outnumbered at Armatura or at the ground at Nurceria? I believe It's made fairly clear in the former and the Ultramarines were only able to land a portion of their forces at Nurceria.

 

Ironically, the Ultramarines were beaten both times not through superior numbers, but by superior tactics. The first being two highly maneuverable, starfort-equivalent ships destroying the orbital defenses along with two fleets of unknown strength, and then two battle barges and a king-ship severely hampering the efforts to land troops. When the Ultramarines left, one battle-barge would be destroyed, another severely crippled. No idea on the losses suffered by the Word Bearers and World Eaters.

 

You seem to miss my point, again. The evidence you cite doesn't actually address or change any of my points provided. The only thing in the former is Lorgar's help and assistance in breaching the defenses of Armatura where they could overwhelm the outnumbered Ultramarines. The latter is more credit to the female Captain that commanded the World Eaters fleet (forgot her name) rather than to the World Eaters themselves. My points stand.

[Kol Saresk]

Well first, let me start out with point out that your point is that the World Eaters and Word Bearers outnumbered the Ultramarines. I also must point out that I never said it was the World Eaters who deployed the superior tactics, only that those two battles were won because of superior tactics. So thank you for repeating what I said, I guess.

 

Betrayer, page 27

 

'You can't attack Armatura with a fraction of your fleet.'

 

Betrayer, page 29

 

'Watch,' he said.

 

'I'm not sure I want to watch two Legions die in the skies above Armatura.'

 

Betrayer, page 30

 

Above and beyond the shipyard was the first concentric ring of void defences. Here, weaponised satellites and fire platforms bristled with turrets, alongside independent landing decks for fighter craft in lockdown.

 

Beyond those, the true defences began. Castles in the sky: great fortress-stations with their own racks of fighters and entire battlements given over to plasma batteries, laser broadsides and ship-killing lance arrays. In highest orbit, the outer sphere of satellites was a three-dimensional spread of solar panels, clockwork engines and slaved servitor brains all connected to vast long-range weapons arrays.

 

Amidst that outermost sphere waited the Evocati fleet. While the Legion mustered at Calth, the XIII Legion's war-world could never be left undefended. The Evocati was comprised of several thousand Ultramarines drawn from a dozen Chapters, awarded the highest honour of all: overseeing the operations of Armatura and the training of new recruits, commanding an Imperial fleet to rival any other.

 

Betrayer, page 37

 

A billion human soldiers. A billion. Not even counting the Titans or Mechanicum skitarii. Not even considering the tank battalions stationed down there. Not even adding in the thousands of Ultramarines Evocati. The numbers had to be exaggerated, or they were all dead.

 

Okay, I think that sums up Armatura not being numbered in the XII and XVII's favor and why they needed the superior firepower of two king-ships to break open the planet. Now on to Nurceria.

 

Betrayer, page 329

 

'Forty-one,' Lehralla said, her voice distant the way it always was when she was seeing through the ship's scanners rather than her own eyes. 'Forty-one enemy vessels.'

 

Betrayer, page 347

 

The Ultramarines drop pods were just the first wave. The XIII Legion came down across the city, deploying in force - even mauled by the loss of Calth, they were still numerous enough to fill Nuceria's heavens.

 

Betrayer page 352

 

Thirty Warhounds. Would it be enough? Audun Lyrac was certain it would - he was equally certain many of them wouldn't survive, and prayed to the Omnissiah that he wasn't about to end his career on his very first walk.

 

 

 

Unfortunately, I can't find any exact numbers of the forces at Nuceria. But there is more than enough evidence that points to it still being an iffy battle until Angron ascended. If you wish, I can and will transcript the sparknotes of the entire battle, from the death of the Fidelitas Lex to Guilliman beating in Lorgar's face to Angron beating in Guilliman's face to the Librarians dying, and even Argel Tal being stabbed in the back by Erebus.

[Gree]

Well first, let me start out with point out that your point is that the World Eaters and Word Bearers outnumbered the Ultramarines. I also must point out that I never said it was the World Eaters who deployed the superior tactics, only that those two battles were won because of superior tactics.<br /><br />Betrayer, page 27<br /><br />'You can't attack Armatura with a fraction of your fleet.'<br /><br />Betrayer, page 29<br /><br />'Watch,' he said.<br /><br />'I'm not sure I want to watch two Legions die in the skies above Armatura.'<br /><br />Betrayer, page 30<br /><br />Above and beyond the shipyard was the first concentric ring of void defences. Here, weaponised satellites and fire platforms bristled with turrets, alongside independent landing decks for fighter craft in lockdown.<br /><br />Beyond those, the true defences began. Castles in the sky: great fortress-stations with their own racks of fighters and entire battlements given over to plasma batteries, laser broadsides and ship-killing lance arrays. In highest orbit, the outer sphere of satellites was a three-dimensional spread of solar panels, clockwork engines and slaved servitor brains all connected to vast long-range weapons arrays.<br /><br />Amidst that outermost sphere waited the Evocati fleet. While the Legion mustered at Calth, the XIII Legion's war-world could never be left undefended. The Evocati was comprised of several thousand Ultramarines drawn from a dozen Chapters, awarded the highest honour of all: overseeing the operations of Armatura and the training of new recruits, commanding an Imperial fleet to rival any other.<br /><br />Betrayer, page 37<br /><br />A billion human soldiers. <em>A billion</em>. Not even counting the Titans or Mechanicum skitarii. Not even considering the tank battalions stationed down there. Not even adding in the thousands of Ultramarines Evocati. The numbers had to be exaggerated, or they were all dead.<br /><br />Okay, I think that sums up Armatura not being numbered in the XII and XVII's favor and why they needed the superior firepower of two king-ships to break open the planet. Now on to Nurceria.<br /><br />Betrayer, page 329<br /><br />'Forty-one,' Lehralla said, her voice distant the way it always was when she was seeing through the ship's scanners rather than her own eyes. 'Forty-one enemy vessels.'<br /><br />Betrayer, page 347<br /><br />The Ultramarines drop pods were just the first wave. The XIII Legion came down across the city, deploying in force - even mauled by the loss of Calth, they were still numerous enough to fill Nuceria;s heavens.

 

i suggest you clean the post up first. It's hard to understand you with all the pagebreaks.

 

Anyway, at least on the Ultramarines I'll let the author speak for me.

 

 

 

Sort of. Remember, there really weren't that many Ultramarines there. A few hundred Ultramarines hammered thousands and thousands of World Eaters and Word Bearers on Armatura (Khârn and co. keep lamenting how they're getting pulped by superior tactics and brotherhood, and running into the Ultramarines' traps), and when a few thousand more Ultramarines show up, still outnumbered, Guilliman holds off two Traitor primarchs on his own.

 

The deal is, it's a story about a disaster suffered by the Ultramarines. So they're not going to win it. I'm still pretty confident they didn't look dumb, though. They slaughtered way, way more World Eaters and Word Bearers than taking casualties of their own.

 

And here.

 

 

 

That's what happens to the World Eaters when the Nails bite. It's why they take such horrendous casualties on Armatura despite massively outnumbering the Ultramarines (they keep charging into ambushes and urban defence traps), and it's why the Space Wolves beat them so soundly on the Night of the Wolf. They have the strength of individual ferocity, but we can look historically at the Romans versus Just About Anyone to see how well an army of individual fighters will fare against organised military tactics. There's a reason the phalanx and maniple systems conquered most of the known world (actually, there're many reasons, but one of them was this): anyone fighting them in broken formation was one man against two or three men, and those two or three soldiers were also defending each other at the same time as they fought for themselves.

 

That's rather the point of the battle. The Ultramarines never really held an advantage at Armatura. They were never going to win it. Yet despite the odds arrayed against them they were able to inflict more losses on the traitors than the WE could do to them.

 

Nuceria is simply the Ultramarines being unable to land most of their troops on the surface. Which is mostly a ragtag force hastily assembled by Guilliman. All tactical innovatuons done in the book where by the Word Bearers or the non-Astartes officers.

 

Which was my point. The World Eaters suffered heavily at the hands of the Butcher's Nails and really could only overwhelm the Ultramarines with numbers. The most important contributions to the Ultramarine defeat was from non-World Eaters.

[GhostMalone]

Kol is in the right here.

[Gree]

Kol is in the right here.

 

He is certainly not. If anything he's proven my point further. The World Eaters where able to defeat the Ultramarines because of non-World Eater support, while Khârn spent a good deal of the book lamenting on how uncontrollable the World Eaters themselves were.

[Kol Saresk]

 

 

Kol is in the right here.

 

He is certainly not. If anything he's proven my point further. The World Eaters where able to defeat the Ultramarines because of non-World Eater support, while Khârn spent a good deal of the book lamenting on how uncontrollable the World Eaters themselves were.

 

 

I wasn't disproving that point. I was disproving that in Betrayer, the World Eaters and Word Bearers only won because of superior numbers. Which, they didn't.

[Gree]

 

 

Kol is in the right here.

 

He is certainly not. If anything he's proven my point further. The World Eaters where able to defeat the Ultramarines because of non-World Eater support, while Khârn spent a good deal of the book lamenting on how uncontrollable the World Eaters themselves were.

 

I wasn't disproving that point. I was disproving that in Betrayer, the World Eaters and Word Bearers only won because of superior numbers. Which, they didn't.

 

They very much did. Not the sole reason admittedly, but larger numbers of World Eaters and Word Bearers outnumbering the Ultramarines certainly played a role in the defeat of the Ultramarines, who, to their credit inflicted heavy losses on the berserk World Eaters on the ground and in such conditions.

[Kol Saresk]

And where are the inferior numbers of the Ultramarines listed? Could you please provide a source or cited pages, as I just did to prove that the Word Bearers and World Eaters were outnumbered at Armatura and more than likely at Nuceria since even the Titans were iffy on numbers?

[Gree]

And where are the inferior numbers of the Ultramarines listed? Could you please provide a source or cited pages, as I just did to prove that the Word Bearers and World Eaters were outnumbered at Armatura and more than likely at Nuceria since even the Titans were iffy on numbers?

 

You proved nothing in the former, merely that Armatura had formidable defenses and only ''several thousand'' Ultramarines present. You proved nothing at the latter.

 

If you want proof I would have to scout my copy of Betrayer for a bit, but I think the author's quotations above should suffice. Even if you take it as his opinion, it's very much the intent that the Ultramarines were outnumbered in said battle.

[Kol Saresk]

So let me get this straight, I could prove that Armatura was defended by not only thousand of Ultramarines, but a billion mortal soldiers, tanks regiments, mechanicum skitarii, a Titan Legio, an entire fleet plus orbital defenses, but because at one point in the battle, hundreds of Ultramarines were charged by the World Eaters, you would say that the defenses of Armatura are outnumbered?

 

As far as Nuceria, well we can't say one or the other unless we know the loading capacity of a Glorianna-class battle-barge and how filled to capacity the Fidelitas Lex and the Conqueror were versus the forty-one ships that attacked and dropping enough troops to 'fill Nuceria's heavens', according to Betrayal page 347.

 

Although how did we get this far off topic?

[Gree]

So let me get this straight, I could prove that Armatura was defended by not only thousand of Ultramarines, but a billion mortal soldiers, tanks regiments, mechanicum skitarii, a Titan Legio, an entire fleet plus orbital defenses, but because at one point in the battle, hundreds of Ultramarines were charged by the World Eaters, you would say that the defenses of Armatura are outnumbered?

No, I was talking about the Ultramarines themselves. I could hardly care about the rest of the forces. I was referencing the nature of the Astartes vs Astartes combat. By the author's own comments on the matter, the Ultramarines were outnumbered when facing the World Eaters.

 

You did read A D-B's comments?

As far as Nuceria, well we can't say one or the other unless we know the loading capacity of a Glorianna-class battle-barge and how filled to capacity the Fidelitas Lex and the Conqueror were versus the forty-one ships that attacked and dropping enough troops to 'fill Nuceria's heavens', according to Betrayal page 347.

 

Although how did we get this far off topic?

That happens on the internet. I really should have never responded to you in the first place. That was a waste of time for me.

[Wade Garrett]

Do we know how many Ultramarines were in the square when Khârn charged their shield wall with "the broken remnants of three companies" and proceeded to tear down said shield wall and butchered all the Ultras?

 

The thing to remember is, the Butcher's Nails don't just drive their wearers insane...they also insure the crazy person is going to be faster, stronger, and regard any injury that isn't instantly fatal as a mild annoyance that can be attended to when the bloodshed stops. Which are wonderful traits for violent psychopaths to posses.

[Gree]

Do we know how many Ultramarines were in the square when Khârn charged their shield wall with "the broken remnants of three companies" and proceeded to tear down said shield wall and butchered all the Ultras?

I don't recall any statement. Khârn seemed to regard it as a ''last stand'' for the Ultramarines although he also noted the World Eaters pretty much had to succeed in the first charge.

 

The only other indication of numbers is this line:

 

"World Eaters gunships juddered overhead, their spotlights raking the ground, scouting ahead of the main forces. He had outriders on jetbikes, as well as recon teams ranging ahead, and for the last few hours they’d played the invasion out as any other Legion would. Rain, doubtless inspired by the atmospheric disturbance of thousands of vessels in low orbit and making planetfall runs to disgorge troops, lashed down in a tidal pour. It did nothing for the dust beyond turning the ground to clinging mud. It did, however, go some way to cleaning the World Eaters bloodstained armour."- Betrayer ebook edition.

 

Apparently the traitors had ''thousands'' of ships still landing troops. I guess you could probably say some of those were Ultramarines, but Armatura apparently only had ''several thousand'' Ultramarines, with most of them evidently deployed on the surface.

[Kol Saresk]

Not specifically, no. If we go by A D-B's post, there were hundreds in the square reinforced by artillery while the total number on the planet(according to the book) were in the thousands. Assuming you want to use an Astartes/Titan versus Army/Astartes/Mechanicum/Titan conflict as a basis for Astartes vs Astartes conflict and discount the billion troops, the Titans that intervened and everything else that was involved.

[Blood Angel Scout]

One thing to point out that will bring your mini-debate to an end and back toward topic CONTEXT.....the context of the end of Betrayer being that a Demon Prince of Khorne is now leading the beserkers, hope/reckon we may see more of the martial theme behind the Blood God, more God of War and that the WE LEGION didn't disintegrate til after the HH and Scouring to what is 40K, remember still 30K here, 1st Foundings and all shiny and new etc

 

So, with regard to context, at this stage of the series, Horus is in command of 9 legions, 3 who have primarchs that have ascended and all the "blessings" that brings against several individually scattered crippled/reduced, isolated and confused legions who by now are only beginning to understand what has happened...the traitors know or at least have been tasked with a battle plan, loyalists are still unsure who it is they are to fight until fired upon, which are ideal conditions for the WE, AL and NL to perform in, while other legions can be used to their merits in securing ground on approach to Terra, all in line with Horus's MO of speartip strike.

 

The only thing that would change if he had different legions would be what legions would do what instead of the existing version, as he sees them as the tools to apply his plan...the players my change but game remains the same, stick to the plan...and until we see the detail/context of how the plan and his entire being came unstuck from the Emp's soulnuke then, at this point in the series, he's on for the win

[Kol Saresk]

So, with regard to context, at this stage of the series, Horus is in command of 9 legions, 3 who have primarchs that have ascended and all the "blessings" that brings against several individually scattered crippled/reduced, isolated and confused legions who by now are only beginning to understand what has happened...the traitors know or at least have been tasked with a battle plan, loyalists are still unsure who it is they are to fight until fired upon, which are ideal conditions for the WE, AL and NL to perform in, while other legions can be used to their merits in securing ground on approach to Terra, all in line with Horus's MO of speartip strike.

 

The only thing that would change if he had different legions would be what legions would do what instead of the existing version, as he sees them as the tools to apply his plan...the players my change but game remains the same, stick to the plan...and until we see the detail/context of how the plan and his entire being came unstuck from the Emp's soulnuke then, at this point in the series, he's on for the win

Yes. And no. If you change the players, the game itself may not change, but how you play does. We can give Horus the fantasy football team of everyone's dreams. The problem is, he is trading the most erratic, bloodthirsty, hard to control Legions for the well-controlled, coherent and organized Legions. He was able to so amply defeat the well-controlled Legions precisely because they were so well-controlled, coherent and organized. He can't use the same plans to knock those Legions out of the fight. If he is willing to suffer the losses, he can easily lure the World Eaters into an ambush and then wear them down to nothing. Change the players, and everything else has to change.

[Wade Garrett]

Something else to consider:

 

Horus's end goal was not just to kill his dad, but to take the throne and rule in his place.

 

We know from Know No Fear and Horus Rising that Dorn, Guilliman, and Sanguinus were all possible candidates for the role of Warmaster. Horus may have chosen Primarchs who he felt would follow his orders (Lorgar, Mortarion) or who had zero interest in ruling anything (Curze, Angron) because he had no intention of winning at Terra and promptly having to fight say, Guilliman or the Lion for the crown.

[GhostMalone]

True, you still want an army under your command.

 

Dad kept them in check whereas no emperor everyone can seek their own agenda

[Stonerhino]

 

 

Isstvan is too horrifying to be preventable or even made less of a massacre by anyone not crazy or paranoid. Which, yeah, does add up a bit in the case of the Emperor's Children.

 

None of the so-called "unpredictable" seem to be doing that badly. The World Eaters ravaged the Ultramarines empire. Same for the Word Bearers, though they keep a lot of hidden agendas. But Lorgar's as commited as they come. The Night Lords only lost the Thramas crusade because of the goddamned thingamagig the Lion found. Perturabo is in a good mental spot, getting fiercer by the day. Fulgrim is the only truly unreliable one, he'll actively destroy the traitor's cohesion if it means a new scale for his tail. The Alphas are extremely efficient. Sure they're very obscure, but they sow confusion and that's an invaluable asset. They contribute to the Ravens' fall, if I recall. Mortarion is a great soldier and probably the best ally Horus has, also one of the few to remain the Warmaster's brother, along with Perturabo.

 

Unpredictability is awesome. No one sees it coming, which in wartime means no one sees anything else.

 

Except the World Eaters aren't unpredictable. The World Eaters are very predictable. They have one main tactic that they almost always use and Angron doesn't even actually ''lead'' his Legion, so much as charge screaming while his men try to pick up the pace behind him. The World Eaters merely have the good fortune to have great superiority in numbers and allies in pretty much every time they fight in the Heresy.

 

I'm rather amused as people trying to present the World Eaters and Night Lords as these unpredictable mavericks, when they're really not. They both have their rather predictable methods of war and temperaments, while lacking in discipline, good leadership and trust.

 

I mean, historically, disorganized and ill-disciplined troops are generally rather crappy troops. If anything, the WE and Night Lords being loosely organized lunatics would make them easier to outmaneuver and defeat.

Regarding Isstvan III, the Warmaster ended up capitalizing on it and having each remaining member of the traitor Legions fight his brothers. Sure, it cost him a lot in lives, but also prevented any future dissidense. And while that wouldn't have been likely, it's one thing to agree to the majority of your 50.000 traitor brothers and 'go with it'. It's another to bathe yourself in your best friend's blood to prove you're with the traitors. Look at Horus Aximand...second thoughts were creeping even after he killed Torgaddon. I'm not saying Angron's move paid off. I'm saying it'd be 100% plausible to see a few stories about members of the traitor Legions having regrets and trying to sabotage the whole thing if Isstvan III had ended with the fire

storm.

A soldier than cannot be controlled is in general, a worthless soldier in the end, no matter how ferocious or unrelenting he may be.

Then why did the Ultramarines not easily beat the World eaters ?

 

I am not through all of the post but to answer your question, the Word Bearers.

[Stonerhino]

Something else to consider:

 

Horus's end goal was not just to kill his dad, but to take the throne and rule in his place.

 

We know from Know No Fear and Horus Rising that Dorn, Guilliman, and Sanguinus were all possible candidates for the role of Warmaster. Horus may have chosen Primarchs who he felt would follow his orders (Lorgar, Mortarion) or who had zero interest in ruling anything (Curze, Angron) because he had no intention of winning at Terra and promptly having to fight say, Guilliman or the Lion for the crown.

Horus also had the issue of only picking legions that he had a good idea would turn.  To much overt action and the Emperor would have found out to soon.  or worse started the Heresy premature.

 

You do have a good point with the idea of not picking legions because they are a threat to your rule.  But first you need the victory before you even can have "Your rule".  With hind sight we can see that Horus made some poor choices.  And truefully he made the choices that he had to.  Maybe not the ones he would have chozen.  See Warmaster for details.

[Greyall]

Ultimately, it'd change too much. It's just impossible to think of Guilliman, Dorn, Sanguinius, Corax, Russ, Ferrus, The Lion or Vulkan betraying the Emperor. The Khan's motivations remain to be seen, it's not the fact that he is friends with Horus, it's normal to trust your friends. What 'worries' me about Jaghatai is his rebellious streak, I fear he may not be loyal enough to the Emperor.

 

But you've seen how the loyalists fight, it's not pretty either. Imagine what Malcador and Valdor would do with the World Eaters in their ranks. Heck, they might even flame Lorgar's religious streak to spur him into a frenzy. I don't see how the outcome would be radically different with the players trading factions. Different tools, different ways to play a game. Who's to say Perturabo wouldn't mount a better defense than Dorn? How do you factor in Chaotic influences?

 

I've mentioned the Blood Angels being even more frenzied than the World Eaters when slightly touched by Khorne, imagine having the Blood God sleeping upstairs every night. Who's to say the Imperial Fists wouldn't give in to Nurgle due to Dorn's rivalry with Perturabo or that Russ and his wolves wouldn't have gone down the Khornish way either...? To be honest, some Traitor Primarchs were very resistant to the Chaotic influence and even those that gave in were caught by surprise. Fulgrim was put in the back of his mind and likely had plenty of time to talk to Slaanesh. Angron was caugh up in Lorgar's gospel-of-Hell. Mortarion was betrayed by Typhon. Perturabo held like a boss, as did Curze and the Alphas.

 

Too many variables, in short. I'll say it again. Horus was just sighing when he wished for different allies, having a "grass is greener" moment.

[Stonerhino]

It has nothing to do with resistance to Chaos.  Some Legions would have just been better to have for the revolt then others.  Horus might have even been able to carry out a protracted war against his father with the backing of the 500 worlds and Gulliman.  Instead of the smash and grab approach he used.  With different Legions he might have ben able to isolate and destroy the loyal legions before even heading to Terra.  Resupplied and rearmed then show up at Terra with the better part of 9 legions.  Rather then the misfits he used in the real heresy.