Russ is on Terra?

[Scribe]

Looking at the old timeline from the HH Weekender (its in that thread again) Russ on Terra/Vengeful spirit, is old old news. I wish I had the whole series so we could actually plot this all out...

 

Either way Wade kills it again.

[Phoebus]

So....the only reason the Alpha Legion didn't leave Russ a frozen corpse in the void was because the Dark Angels came in like the cavalry.

 

Russ's new plan is to go straight for the Sons of Horus, a Legion that is larger and more accomplished than the XX, who are also traveling with the Death Guard.

 

Wow. So executioner. Such planning. Much brilliant. Very tactician.

 

Hence my earlier point.  The standard was set when Ferrus Manus decided the best approach to beating Horus on Isstvan V was to land on the planet, advance through a meticulously prepared kill-zone, and assault a heavily fortified position - all with a significantly outnumbered force.  His tactics, such as they were, amounted to "You go left, you go right, and I'll take the middle!"  By that standard, is Russ's plan that jarring?

 

I don't think so - but that's just me.

 

Russ is basically proposing that he can overcome 4-1 odds (or better, or worse) long enough to get on the Vengeful Spirit and put his hands around Horus.  That's actually not bad compared to some of the craziness other primarchs have come up with.  Sure, it's not on par with the sober hit-and-run routine that Curze pulled off for two years against the Lion.  It's not the seminal come-from-behind effort Guilliman made at Calth.  But it's not Angron's "Greatest Hits of Stragedy" (I spelled it that way on purpose), either.

 

HonestIy, the only part of Russ's plan that I found zany was the "Pathfinder Mission", which basically amounted to forced drama/a way to get the Knights Errant involved.

[Leif Bearclaw]

Have to come to the defence of The Gorgon here. His plan for Istvaan is a lot less stupid than Russ' apparent 'I'm gonna go pick a fight with Horus of my own' plan. The loyalists weren't massively outnumbered, both the DG and EC could put fewer Astartes in the field than any of the 1st bwave after istvaan III (this is a little tricky though, because Massacre doesn't tell us how many of the X were actrually deployed, only that the ground war and fleet action cost them tens of thousands), plus the loyalists made it through the kill zone and were inflicting heavy losses of the Traitors. But chiefly that ignores the principal failing of the Istvaan V attack. More than half the forces deployed were actually on Horus' side. That is what cost the Loyalists, not some flaw in Ferrus' plan. If another 4 loyal Legions had been backing the first wave, is there any doubt the Traitors would've been crushed?

[Kol Saresk]

Well, Massacre does and doesn't tell us how much the X fielded. Fulgrim tells us that the first wave was ten thousand, an was then followed by the rest of the 52nd Expedition. Massacre tells us that the 52nd totaled at two-thirds of the Legion's strength. So at 113,000, the X Legion ultimately put out something in the neighborhood of 75,000 troops, plus their armoured regiments.

[RapatoR]

Now I can't get rid of the mental image of Space Wolves as legion of dodges. Thanks Wade.

[Leif Bearclaw]

Well, Massacre does and doesn't tell us how much the X fielded. Fulgrim tells us that the first wave was ten thousand, an was then followed by the rest of the 52nd Expedition. Massacre tells us that the 52nd totaled at two-thirds of the Legion's strength. So at 113,000, the X Legion ultimately put out something in the neighborhood of 75,000 troops, plus their armoured regiments.

But even then, we don't know how many of those 75,000 made it planetside, how many died on their ships, and how many got away. Or are those numbers hiding somewhere?

[Kol Saresk]

True. But that can also be said of any of the Legions that were there.

[Leif Bearclaw]

True, but at least as far as the Loyalists go, we have the least specifics about the X (at least as far as I'm aware). Especially as they had their Legion fleet dripping into the massacre thanks to the fastest ships going on ahead. We know that 80,000 RG deployed and only 3000 got out, and something like 83,000 Salamanders were sent, and they suffered 98% losses, so that's only 1660 escaping Istvaan.

[Kol Saresk]

Well, not entirely true. We know about 3,000 made it back to Deliverance. We know Sharrowkyn is out there somewhere and there are also the ones who made it to Ultramar, but we don't have specifics on numbers. The Salamanders are even worse, but then again, they're suppose to be.

[Phoebus]

Have to come to the defence of The Gorgon here. His plan for Istvaan is a lot less stupid than Russ' apparent 'I'm gonna go pick a fight with Horus of my own' plan. The loyalists weren't massively outnumbered, both the DG and EC could put fewer Astartes in the field than any of the 1st bwave after istvaan III (this is a little tricky though, because Massacre doesn't tell us how many of the X were actrually deployed, only that the ground war and fleet action cost them tens of thousands), plus the loyalists made it through the kill zone and were inflicting heavy losses of the Traitors. But chiefly that ignores the principal failing of the Istvaan V attack. More than half the forces deployed were actually on Horus' side. That is what cost the Loyalists, not some flaw in Ferrus' plan. If another 4 loyal Legions had been backing the first wave, is there any doubt the Traitors would've been crushed?

Let's be clear about what source I'm working from: the novel Fulgrim. Within the context of the novels, Ferrus Manus's plan amounts to nothing more than a shock frontal assault:

 

“The Morlocks and I will take the vanguard,’ said Ferrus. ‘Corax, your Legion is to secure the right flank of the Urgall Depression and then push into the centre. Vulkan, you have the left wing.”

 

Excerpt From: Graham McNeill. “Fulgrim.” iBooks.

What makes it inexcusable is the context of his situation. He's basically outnumbered 3:2 or 4:3 and assaulting through a prepared killing zone and a heavily fortified position. If he waits a few more hours, he can (theoretically; we all know he can't, because he's being "reinforced" by traitors) do the same thing while outnumbering Horus's forces by at least the same ratio. His qualifier - that they can't waste the element of surprise - is a zinger all in itself. It assumes Horus wasn't able to detect the arrival of two-point-something legions arriving in-system. It assumes the Warmaster didn't have his men on combat footing. Corax and Vulkan express reservations about his plan, but stay quiet. The end result of their assault? No surprise: it doesn't work. The bulk of the assault force has to withdraw to the dropsite, while Ferrus presses on with his suicidal advance. Had the other four legions been genuinely coming to his aid, Ferrus would have had to eat a giant helping of crow. Corax and Vulkan would never have let him forget the Raven Guard and Salamanders he wasted on the Urgall for the sake of his pride and rage.

 

Unlike Ferrus Manus, Russ is not taking a theoretically advantageous situation and letting his emotions turn it into a disadvantage. Nine legions have gone traitor. Guilliman is, essentially, a renegade. Sanguinius probably is as well (at this stage of the game). Vulkan is missing and his Salamanders are all but annihilated. Corax has a few thousand Space Marines left, but the Raven Guard are no longer a viable main-line force. The Iron Hands are loyal, but they too are doing their own thing. The loyal forces that the Emperor can count on amount to the Dark Angels, the White Scars, the Imperial Fists, and his own Vlka Fenryka - which has been mauled twice over. In that light, Russ's effort amounts to a sacrificial chess move. He's a Bishop willing to let himself be taken off the board, so long as he gets to eliminate the enemy's Queen in the process. Is that move a game-changer? Russ and Malcador both seem to think so, even if the latter feels that keeping Russ and the Rout at Terra is the safer strategy.

 

As for the feasibility of Russ's plan, Vengeful Spirit shows that there are ways to incorporate subtlety and deception in seemingly straightforward void warfare tactics. We know that Russ is capable of subtlety: see his conversation with Malcador re: his hidden hunters, watching his flanks. Ferrus Manus, by contrast, didn't even consider adding nuance to his shock assault - neither in Fulgrim or in Massacre. Despite being outnumbered, he was going to smash into the traitors and push on until the Alpha Legion, Iron Warriors, Night Lords, and Word Bearers arrived to restore parity to the fight and win him the battle.

 

Does Forge World's Massacre cast Ferrus Manus in a more positive light? Yes, to a degree. They expand a good deal on the action, provide graphics that show individual objectives, and - in general - give a better perspective of the overall battle. Where Ferrus's depiction is concerned, Massacre also includes a key detail that compliments the Gorgon: his planet-side assault is expertly executed, and gets his vanguard as close to the void shields protecting Horus's fortifications as possible. This mitigates the prepared killing zone of the Urgall Depression to an extent, and makes his otherwise straightforward assault viable.

 

That's about as far as Forge World goes in making look Ferrus look better, though. Everything that's wrong with his approach, planning, and tactics in Fulgrim is still wrong here. Corax and Vulkan still don't look jazzed about Ferrus's consuming need to smash bad guys with the odds stacked against him. No one seems to think it's weird that four legions' worth of fleets are nowhere to be found.

 

A closing point: Credit to Forge World for taking Fulgrim's lemons and making lemonade out of them to the extent that they could. You have to take that into consideration when judging the merits of Russ's plan, though. You have to assume that Forge World would also give Russ that courtesy (if such a mission was actually to be undertaken).

[Phoebus]

Random side-rant:

 

I hope someone who writes good fan-fiction tackles Horus's perspective of the Isstvan V Dropsite Massacres in a comical way.  I am convinced that Horus expected Ferrus to wait for his other four brothers and attempt an attack with overwhelming force.  The ideal scenario for him would have been to sit behind the remarkable fortifications the Dark Mechanicus had erected out of the xenos ruins and the Urgall Depression and catch the Iron Hands, Raven Guard, and Salamanders in a ridiculous crossfire before they even got into his lines properly.

 

I imagine Horus went ballistic when he realized Ferrus went Full Gorgon on him, since that meant that thousands of Sons of Horus, Death Guard, Emperor's Children, and World Eaters would die needlessly.  :D

[Wade Garrett]

@ Phoebus:

 

If you're going to declare Guilliman and Sanguinus renegades based on the events of "Unremembered Empire", then so are the Lion and the Dark Angels, what with Johnson signing off on the whole "The Emperor is most likely dead! Long live the Emperor!" ploy of Imperiun Secundus.

[Conn Eremon]

And the White Scars were still an unknown factor at that time, with more tied to the Traitors than the Loyalists.

[Kol Saresk]

Actually, not really. In Fulgrim, Ferrus is attacking four worn down and bloodied Legions with three fresh(ish) Legions with four more coming behind. His "frontal assault" was a beachhead. And in that context, he succeeded. There was really no alternative. Too many ships in orbit to just bombard the fortified, void-shielded fortress, so the only other thing to do is, well knock.

 

And the plan was also a sound one-two punch. First wave drags the Traitors out and bloods them, and the second crushes them. It wasn't Ferrus' fault that he had been outplayed by Horus.

[Scribe]

Ferrus didnt pull back as planned however...

[Kol Saresk]

That was after the fact. And as you just said, "Not part of the plan".

[Scribe]

I'm in a sickness and drug fueled semi-coma, but actually wasnt Ferrus always in disagreement with the whole 'retreat' part?

[Leif Bearclaw]

Can't really comment in any detail about the plan in Vengeful Spirit, as everything I know about it I've picked up from this thread.

 

But as far as Istvaan V goes (bear in mind it's something like 6/7 years since I read Fulgrim):

 

As I remember the maps in Massacre, the three 1st wave Legions pretty much filled the front at the Urgall Depression, so the Loyalists would be looking at two waves anyway, as trying to pack 7 Legions into that space would be letting the Traitors maximise any killzone effect. Like Kol said, first wave to tie up the Traitors, second wave to finish the job.

 

Of course Corax and Vulkan aren't particularly jazzed about the plan, it's going to be bloody, even if 100% successful, and they don't have as strong a vengeance motive as Ferrus to cloud that realisation. But they're faced with an entrenched, shielded enemy leaving them little option but the frontal assault, bombardment would be rendered moot by the voids, and Istvaan III had already demonstrated how ineffective exterminatus could be on prepared Astartes.  And the odds weren't stacked against him, 7 Legions vs 4 bloodied Traitor Legions, numbers should have been on his side.

 

As for the absence of the Traitor's fleet, what else were the Loyalists meant to do? Stand around because the fleet was elsewhere? Retreat? Really they did the only thing they could do, continue with their mission of attempting to destroy the traitors.

[Phoebus]

@ Phoebus:

If you're going to declare Guilliman and Sanguinus renegades based on the events of "Unremembered Empire", then so are the Lion and the Dark Angels, what with Johnson signing off on the whole "The Emperor is most likely dead! Long live the Emperor!" ploy of Imperiun Secundus.

I still may, depending on how the events of the next few novels and short stories play out. Last Corswain knew, the Lion was going to demand answers from Guilliman. He thought his primarch was prepared to inflict violence on Macragge if Guilliman ended up being a traitor (or what have you). Based on Leman Russ's news, Malcador and the Emperor are both treating the Lion as loyal. I don't see why Russ would not.

Actually, not really. In Fulgrim, Ferrus is attacking four worn down and bloodied Legions with three fresh(ish) Legions with four more coming behind. His "frontal assault" was a beachhead. And in that context, he succeeded. There was really no alternative. Too many ships in orbit to just bombard the fortified, void-shielded fortress, so the only other thing to do is, well knock.

And the plan was also a sound one-two punch. First wave drags the Traitors out and bloods them, and the second crushes them. It wasn't Ferrus' fault that he had been outplayed by Horus.

Kol,

Before we get way deep into this, I want to remind you of my original point, to Wade. I'm not using Isstvan V to argue that Ferrus is an idiot. I'm trying to point out that we have to balance the in-universe fact that primarchs are brilliant strategists and tacticians with the real-world fact that the primarchs' actual strategies and tactics are determined by science fiction authors. In that light, we have to be careful about making light of Russ's grand plan to kill Horus without viewing it within the context of the setting - and its writers' limitations.

That's all I'm ultimately trying to get at.

Now, that having been said... you know I'm a sucker for a debate! I went ahead and threw in my points in a spoiler, even though I suspect we'll eventually agree to disagree with one another.

Any way you cut it, the initial odds were against Ferrus. Probing attacks often use numerically inferior elements, I'll grant you that. So do feints. Reserves are also held for the purposes of exploiting flanks or defending them. All that makes sense. Ferrus Manus, on the other hand, threw practically everything he had into the fight - despite categorically knowing that he was going uphill (literally) against a numerically superior and fortified enemy - and his follow-on act was going to be to throw everything he had into the fight again. That makes no sense to me.

Beyond that, we need to make sure we're working with the same technical terms before this discussion goes awry. Please bear with me. I'm not trying to be a jerk; I just want to make sure we're on the same page.

A beachhead is a temporary line created when a unit reaches a certain point and defends it until follow-on forces arrive and operations can continue or commence properly. Agreed?

Ferrus Manus achieved his beachhead at the very beginning. Proof of that is the fact that his follow-on forces forces (the balance of the Raven Guard and Salamanders legions) were able to land and deploy in good order. His follow-on assault on the Urgall Depression was exactly that: an assault - a very straightforward assault. Page 37 of Massacre qualifies, I think, that Ferrus's assault did not succeed. The beachhead? Yes. The assault? No. It was a dreadfully costly stalemate, which ended up with the majority of his force withdrawing. "Tens of thousands" of the Space Marines under Ferus's command were lost, in large part because they attacked a numerically superior enemy.

Nothing about Ferrus Manus's plan would have suffered had he waited for the other four "loyal" legions to arrive (well, other than that whole betrayal thing). Any traitor forces that took advantage of those hours to venture outside the void shields and potentially contest the drop sites themselves would have been annihilated by the orbital barrages - Massacre makes that abundantly clear. He still would have led a vanguard that still would have landed at the edge of the void shields, and still would have been able to launch a follow-on assault once the second wave landed. The difference is that said second wave would not have been just the balance of the Raven Guard and the Salamanders. It would have been roughly six legions strong.

The proposed alternative is launching an assault with a force that is numerically inferior and qualitatively (man for man) no better than the defenders. And then launching a second assault with just the four fresh legions or with the badly mauled (and, potentially, exhausted) survivors of the first wave, as well. Again, that doesn't make sense to me... but such is life!

[Phoebus]

Can't really comment in any detail about the plan in Vengeful Spirit, as everything I know about it I've picked up from this thread.

 

But as far as Istvaan V goes (bear in mind it's something like 6/7 years since I read Fulgrim):

 

As I remember the maps in Massacre, the three 1st wave Legions pretty much filled the front at the Urgall Depression, so the Loyalists would be looking at two waves anyway, as trying to pack 7 Legions into that space would be letting the Traitors maximise any killzone effect. Like Kol said, first wave to tie up the Traitors, second wave to finish the job.

 

Of course Corax and Vulkan aren't particularly jazzed about the plan, it's going to be bloody, even if 100% successful, and they don't have as strong a vengeance motive as Ferrus to cloud that realisation. But they're faced with an entrenched, shielded enemy leaving them little option but the frontal assault, bombardment would be rendered moot by the voids, and Istvaan III had already demonstrated how ineffective exterminatus could be on prepared Astartes.  And the odds weren't stacked against him, 7 Legions vs 4 bloodied Traitor Legions, numbers should have been on his side.

 

As for the absence of the Traitor's fleet, what else were the Loyalists meant to do? Stand around because the fleet was elsewhere? Retreat? Really they did the only thing they could do, continue with their mission of attempting to destroy the traitors.

 

I think this comes down to the forced drama that we sometimes see in this series.  Sometimes, this is a product of the author's lack of imagination.  For instance, some of the factors that determined the outcome of the Isstvan V Dropsite Massacres come down to "because".  You could, for instance, apply that to the very beginning of the battle:  why were the dozens and dozens of capital ships and strike cruisers not able to beat down the void shields protecting Horus's forces?  "Because".  I'm not trying to be a jerk here, but this is almost literally a case of plot armour.  ;)

 

Sometimes forced drama arises due to the author's limitations.  Not everyone will be able to do D-Day justice, for instance, because General Eisenhower, Lieutenant Colonel James Gavin, and Staff Sergeant William "Wild Bill" Guarnere had perspectives and experience not easily attainable by someone who writes fiction.  Again, that's not a knock on Graham or whoever else.  I don't even have the perspective and experience needed to write a novel capturing other people's perspective and experience, so it's not as if I think my limited military experience gives me license to insult the man!  :)

 

And sometimes, to be fair, the author is just painted into a corner.  Isstvan V was an established event years before Fulgrim was written.  Graham had to adhere to certain facts no matter what his personal opinion was.  I don't think it makes much sense for Space Marines to fight their signature battle of the setting on the ground, through conventional land battle... but there it is.

[Wade Garrett]

As I recall it, the World Eaters, Death Guard, Sons of Horus, and the Emperor's Children had to cull something like a third of their own numbers at Isstvan III, in addition to the casualties inflicted when Angron turned a simple "Nuke'em from orbit" into "GLORIOUS HAND TO HAND MELEE BECAUSE HONOR AND STUFF!" so the numbers might have been a bit more even for the Ravens, Salamanders, and Iron Hands.

 

Although probably not to the...what is it, 3 to 1 numerical advantage you're supposed to have assault a fortified position with any hope of success? (Is himself going by sci-fi and fantasy novels, thus unsure of his figures).

[Phoebus]

Yeah, I doubt the odds were greater than 4:3 or 3:2 in Horus's favor.  The Sons of Horus are thought to have had 70-110,000 Space Marines after Isstvan III.  The Emperor's Children had as few as 60,000 Space Marines after Isstvan III.  The World Eaters were estimated as having about 150,000 Space Marines, of which 75% went to Isstvan III.  A third of those were culled.  The Death Guard had about 95,000 Space Marines.  Worst case scenario, the traitors should not have had less than 240,000 warriors at Isstvan V.  That's assuming the Death Guard also culled about a third of their numbers, and that both they and the World Eaters lost an additional 25-30% of their warriors in the process of doing so.

Against that, we have the 83,000 Salamanders spoken of in Massacre, and I think roughly 90,000 Raven Guard.  To them, you can add however many Space Marines the Clan Avernii numbered.  I'm assuming there's a minimum of nine Clans of the Iron Hands, which means Ferrus Manus brought at least 12,000 warriors with him.  Or less.  I'm not sure!

 

Either way, it seems the Traitors' biggest advantage was being well-fortified.

[Conn Eremon]

79-80k Raven Guard.

[Leif Bearclaw]

Ferrus Manus achieved his beachhead at the very beginning. Proof of that is the fact that his follow-on forces forces (the balance of the Raven Guard and Salamanders legions) were able to land and deploy in good order. His follow-on assault on the Urgall Depression was exactly that: an assault - a very straightforward assault. Page 37 of Massacre qualifies, I think, that Ferrus's assault did not succeed. The beachhead? Yes. The assault? No. It was a dreadfully costly stalemate, which ended up with the majority of his force withdrawing. "Tens of thousands" of the Space Marines under Ferus's command were lost, in large part because they attacked a numerically superior enemy.

Nothing about Ferrus Manus's plan would have suffered had he waited for the other four "loyal" legions to arrive (well, other than that whole betrayal thing). Any traitor forces that took advantage of those hours to venture outside the void shields and potentially contest the drop sites themselves would have been annihilated by the orbital barrages - Massacre makes that abundantly clear. He still would have led a vanguard that still would have landed at the edge of the void shields, and still would have been able to launch a follow-on assault once the second wave landed. The difference is that said second wave would not have been just the balance of the Raven Guard and the Salamanders. It would have been roughly six legions strong.

The proposed alternative is launching an assault with a force that is numerically inferior and qualitatively (man for man) no better than the defenders. And then launching a second assault with just the four fresh legions or with the badly mauled (and, potentially, exhausted) survivors of the first wave, as well. Again, that doesn't make sense to me... but such is life!

The plan of waiting does impose some questions, such as would the Urgall Depression be a viable landing zone after a few hours of sustained orbital bombardment? It's entirely possible that it would destroy the ground, rendering it impossible for the Loyalists larger landers and heavy gear to be landed successfully.

As for the assault itself, it was always going to be a costly slugging match, everyone knew that going in. Was Ferrus too impulsive with his attack, not waiting for all his troops, and his refusal to retreat? Yes. However, these mistakes, while still potentially costing Ferrus his life, would not have changed the outcome if both waves had been loyal. They could afford to keep slugging it out, Horus would run out of men before they did.

Tbh, when you sum up the plan like that, it has a distinct similarity to Soviet WW2 tactics, which, though brutal and costly, did work. Also it's worth remembering that the defenders would be as exhausted as the first wave, and didn't have reinforcements. If they'd been loyal (and Ferrus hadn't gone a bit crazy once he landed), you have a situation where the 7 loyal Legions can cycle in and out of the attack, resting and rearming, while the Traitors get no respite. While this effect would have been possible with 1 landing, I think it's a safe assumption that each Legion would work better as a single entity, so landing and attacking in 2 waves gives each attacking Legion the chance to bring it's full force to bear, as opposed clogging up a battlefield with 7 Legions attacking on narrower fronts. The latter also has more potential fracture points between the Legion, as the inter-legion support, comms and coordination is probably not as tight as it is within each individual Legion.

I think this comes down to the forced drama that we sometimes see in this series. Sometimes, this is a product of the author's lack of imagination. For instance, some of the factors that determined the outcome of the Isstvan V Dropsite Massacres come down to "because". You could, for instance, apply that to the very beginning of the battle: why were the dozens and dozens of capital ships and strike cruisers not able to beat down the void shields protecting Horus's forces? "Because". I'm not trying to be a jerk here, but this is almost literally a case of plot armour.

And sometimes, to be fair, the author is just painted into a corner. Isstvan V was an established event years before Fulgrim was written. Graham had to adhere to certain facts no matter what his personal opinion was. I don't think it makes much sense for Space Marines to fight their signature battle of the setting on the ground, through conventional land battle... but there it is.

On the first point here, while the answer does contain some 'because', there is some in fluff justification/precedent. It's a general point of the setting the orbital bombardments rarely worry surface installations with intact voids. I believe this is generally due to the plasma generators that power such tech are able to either be bigger, and/or can put all their output towards shields, whereas the equivalent generators on ships have to dedicate their output to life support, engines, weapons etc, so they never have 100% for one purpose. So its more of a setting wide 'because' than a specific issue with Istvaan V.

On the second point, if we apply too much logic, then most of the fights in 30k/40k should really be void war and boarding assaults, especially with Astartes. After all, it takes day/months for a conventional fleet to reach its target from jump points, plenty of time to intercept with space assests, and not endanger your planet based resource/logistic network. But how many time, outside of old BFG fluff, are invaders ever stopped in space?

[Kol Saresk]

Clan Avernii at least numbered 10,000 Morlocks. Plus the 80,000 and 83,000, the total rounds to 173,000. Plus the remainder of the 52nd Expedition not far behind, totaling at two-thirds of the X Legion's strength, the number goes up to 238,000. The Sons had 70,000 left afterwards, plus the EC's 50,000 survivors plus the World Eaters ~100,000(one-third was betrayed), they were facing ~220,000 plus whatever Death Guard survivors there were. And that's just the Astartes. Not a 1:1 ratio for sire, but not a 2:1 either since the Death Guard only numbered 95,000 before Istvaan III so the Traitors definitely are not 346,000-576,000 strong in just Astartes. At least, not until the other four Traitor Legions showed up.