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Of all the Traitor Primarchs, these three seem to have the weakest, and most contradictory motivations. Are they just poorly written, or am I missing something?

Mortarion professes to despise Psykers, yet throws his lot in with the powers of the Warp. He claims to have unbeatable endurance and will, yet is broken down by Nurgle, and begs for salvation. He supposedly hates tyrants, yet eagerly becomes one, and bends the knee to an evil God. I mean, there's hypocrisy and double-standards, then this is a bit much.

Magnus is the worst though. I can understand why he abandoned the Imperium, but why actively join the Traitors? If he's truly a devotee of the manipulative Tzeentch, then surely he must have realised Horus set him up? So why immediately throw his lot in with him? Sure, he was trying to save himself and his Legion, but when they all get turned to dust, why stay loyal to Chaos then? For a Demon Prince of Tzeentch to be such a fool is akin to a Prince of Khorne being scared of the sight of blood.

The only real mitigation I can think of in the examples of Magnus and Mortarion is that the process of attaining Demonhood may strip away some free will, and as both were under duress at the time, may no longer be able to rebel against their new masters, despite, effectively, having been screwed by them.

Perturabo is different, in that he's clearly pretty evil from the start. He's massively insecure and spiteful, to the point that he decimates his own legion when still loyal, just because he feels they've made him look bad by not being the absolute best out of all the legions.

His inconsistency though is that he supposedly has no loyalty to the Gods of Chaos, being someone governed by logic, and in fact despairs at Fulgrim's transformation into a Demon Prince, yet ends up fully embracing Chaos and Demonhood himself, instead of following the Night Lords example. He rebels, partially, because he feels used and unappreciated, yet stays loyal to the Traitors despite Fulgrim trying to kill him.

I think the point of the Primarchs falling was to solidify Chaos's far reaching and immense power.
Mortarion and Magnus, were the most powerful created in their particular field, second only to the Emperor in all of real space.
The devoted attentions of Nurgle and Tzeentch completely broke the wills of two of the most powerful beings in the galaxy.
Mortarion and Magnus were completely outclassed by ancient entities beyond their level, or comprehension for that matter.

Perturabo was pooped on by everyone who looked at him. Now he wants to poop on people. Fair enough.
I think he was trying to find someone who would care about him.
Or maybe he just said Feth it.

Mortarion more or less joined Horus for nebulous reasons, but he didn't actively join Nurgle of his own free will. He got stuck in the Warp and was forcefully brought into Nurgle's corrupting influence via horrible disease.

Magnus was pretty much forced to betray the Imperium because the Emperor got mad at him for screwing up his plans for the Imperial Webway and sent Russ after him. Russ was then was manipulated by Horus into thinking Magnus was a traitor, and so Russ tried to kill him instead of just bringing him back for a scolding like he was originally ordered. Magnus assumed his father wanted him dead, and he was basically like "I was trying to help you and this is how you treat me? Screw this." Tzeentch provided Magnus with knowledge and sorcery that the Emperor refused to allow Magnus to explore and study; very hypocritically, I might add. It makes sense that Magnus would want to join up with Tzeentch after he left the Imperium. I also would like to note that Magnus is far from buddy buddy with Horus and his followers. In fact, I think there's some fluff that Magnus actually refused an audience with Abaddon when he was trying to recruit forces for his Black Crusades.

Perturabo is perhaps the most justified traitor. The guy wasn't "evil" from the start. He was incredibly bitter and angry at everyone because he and his Legion got the short end of the stick at every opportunity. His entire Legion and he were disrespected at every opportunity, never getting any credit or recognition for the things they did for the Imperium. Peturabo was a brilliant inventor and tactician, but his own brothers treated him like the redheaded stepchild. The Iron Warriors turned traitor because they thought they would finally get some damned recognition for all the work they put in, which they clearly weren't going to get under the Imperium's banner. It's possible that Perturabo accepted Daemonhood because it was a sign of someone (the Chaos Gods) recognizing his worthiness and gave him something he had been refused up to that point: a reward for his deeds.

The point with Magnus though is that surely, as a Prince of Tzeentch, the master of plots, he should be able to understand that Horus tricked him? And if the main reason he turned to Chaos was in a moment of weakness to save his legion, then surely he must understand that Tzeentch played him? Especially after virtually his legion gets turned to dust, rendering the entire reason for his rebellion moot.

Why stay loyal to Tzeentch and Chaos when they betrayed him and screwed him over way more than the Emperor did? If he's not aware of those facts, then he's pretty bad at the whole Tzeentch-ing thing.

I would argue Perturabo was evil from the start. He murdered 10% of his legion, because he was insecure and bitter. He's essentially the school-shooter of the Primarchs. He feels nobody appreciates his genius, so he'll kill them all. That'll show 'em! I appreciate evil is tricky to define (especially when separating from mental illness) but I feel Perturabo was. He put his own petty ego ahead of billions of other people's lives.

I agree that he probably took Demonhood as he saw it as finally getting the recognition he deserved. In retrospect, I can see his motivations. I just feel they were the most pissy of everyone's (which, to be fair, is the point of his character)

Mortarion just seems like an idiot, with ideas above his station and ambition beyond his reach, and gets justifiably punished for his hubris. He picked a losing horse, and despite possibly being the only one to realise he may have not entirely thought this whole Heresy thing through (while trying to turn Jaghati Khan) rode it to the end anyway.

They might be poorly written, but they might also just be very flawed.

Hierophant wrote:
Mortarion professes to despise Psykers, yet throws his lot in with the powers of the Warp. He claims to have unbeatable endurance and will, yet is broken down by Nurgle, and begs for salvation. He supposedly hates tyrants, yet eagerly becomes one, and bends the knee to an evil God. I mean, there's hypocrisy and double-standards, then this is a bit much.

Jaghatai Khan calls him out on this in Scar. Basically, Mortarion threw in his lot with the wrong crowd and realised too late his mistake. At some point doing the Horus Heresy, he tried to recrute Khan in an effort to quell the spread of sorcery within the traitor ranks. He didn't get anything out of it tho since Khan would have none of that, and their wasn't any other primarch within the traitors ranks, who would support him in this.

Khan: But it has gone wrong hasn't it? You have completed your great mission, but there are more sorceres than ever. Horus has sponsored them, Lorgar has shown them new tricks.

Khan: They played you well. You have done their work for them, and soon you will be dragged into it yourself, as warp-sick as they are.

Khan: You've tasted the fruits of treachery and found them bitter. Don't drag me into your ruin. You're on your own, brother.

And on the subect of tyranny.

Mortarion: We are all tyrants. Do not fool yourself. We were bred for nothing else.

Hierophant wrote:
Magnus is the worst though. I can understand why he abandoned the Imperium, but why actively join the Traitors? If he's truly a devotee of the manipulative Tzeentch, then surely he must have realised Horus set him up? So why immediately throw his lot in with him? Sure, he was trying to save himself and his Legion, but when they all get turned to dust, why stay loyal to Chaos then? For a Demon Prince of Tzeentch to be such a fool is akin to a Prince of Khorne being scared of the sight of blood.

He most likely can't reject orders from Tzeentch, now that he has become his underling.

Hierophant wrote:
Perturabo is different, in that he's clearly pretty evil from the start. He's massively insecure and spiteful, to the point that he decimates his own legion when still loyal, just because he feels they've made him look bad by not being the absolute best out of all the legions.

His inconsistency though is that he supposedly has no loyalty to the Gods of Chaos, being someone governed by logic, and in fact despairs at Fulgrim's transformation into a Demon Prince, yet ends up fully embracing Chaos and Demonhood himself, instead of following the Night Lords example. He rebels, partially, because he feels used and unappreciated, yet stays loyal to the Traitors despite Fulgrim trying to kill him.

Perturabo was a spiteful and malicious little git. It is as simple as that. No one liked him since there was nothing likeable about him in the first place.
You could say, that Perturabo's primary goal was to be granted a new purpose in life. Now Hours, he had other ideas about it. Much ike Mortarian and Angron, Horus used Perturabo like a tool.

Hierophant wrote:
His inconsistency though is that he supposedly has no loyalty to the Gods of Chaos

While he may not owe any loyalty to the chaos gods, he does have a connection the the great eye, someting that was unique amongst the primarchs. Perturabo was likely corrupted very early in his life.





Automatically Appended Next Post:

 Darth Bob wrote:
Perturabo is perhaps the most justified traitor. The guy wasn't "evil" from the start.

The guy was undeniably evil from the very beginning. Remember, the first thing he did when he took command over his legion, was to have every 1 out of 10 of his sons beaten to death. And all that for the simple crime of not being the best legion in existence.

 Darth Bob wrote:
His entire Legion and he were disrespected at every opportunity, never getting any credit or recognition for the things they did for the Imperium.

They got a whole lot of respect from Guilliman and the Ultramarines, right up to the point where Perturabo took charge of the Iron Warriors.

 Darth Bob wrote:
his own brothers treated him like the redheaded stepchild.

And for obvius reasons...

 Darth Bob wrote:
The Iron Warriors turned traitor because they thought they would finally get some damned recognition for all the work they put in, which they clearly weren't going to get under the Imperium's banner.

They turned traitor because they slaughtered the inhabitants of their homeworld and joined Horus rebellion as an convenient way to avoid sanction for their crimes.

hopefully the next Graham McNiell book 'Crimson King' will give us more info on Magnus' decision to join Horus.


Automatically Appended Next Post:
I have a theory tho.

The Emperor asks Magnus to sit on the Golden Throne.

Magnus realises that this will involve an eternity of isolation, unbearable pain and torture.. and that he is effectively required to give up all of his ambitions...

.. and he decides he'd rather not.

Magnus hasn't yet turned to Chaos in his personal story line. He's fled Prospero and set up shop in the Eye of Terror, but he hasn't yet shed his mortal form, nor has he devoted himself to Tzeentch.

Not sure about that.. at the end of a thousand sons it does look that way.

He certainly doesn't portray himself as a slave of tzeentch. Doesn't mean he isn't.

Rather than state Perturabo had good reasons to do what he did, I'd actually argue he was probably one of the most evil of the Traitors. A lot of the others reasons may have been weak, but at least you could kind of understand them. Purturabo's were just childish.

Angron and Kurze were mentally ill, and neither particularly wanted to be a Primarch, and neither was given the help they needed, and in Kurze's case, requested.

Horus was arguably fundamentally altered on Davin. When he's killed by the Emperor, it's mentioned he regains his freedom of thought moments before death as the Gods withdraw their power from him., and is horrified by his actions, essentially making him a puppet more than a free agent.

Alpharius/Omegon are possibly still loyal, or were manipulated into doing something they thought good.

Magnus was an idiot, but was tricked into a no-win situation. He turned purely in order to survive.

Lorgar went to Chaos knowingly and freely, but he was never anything other than honest about his motivations. He wanted to serve a higher power by design, and it was hardly his fault the only higher powers were evil. Of course, he could have gone against his own nature - that he chose not to is evil in itself - but he's arguably more a conduit for evil. If the Gods were good, he probably would be too.

Mortarion is a weird one, as his betrayal is the least explained. However, he has doubts about Chaos, and is only fulled turned in a situation similar to Magnus.

Perturabo is spiteful, hateful, jealous and petty from the start. His sole complaint is the incredibly pathetic justification of 'nobody appreciates me', despite, off the bat, doing everything he could to make sure everyone had good reason to dislike him. His only real competition in the unjustified evil book is Fulgrim, who turned for similar reasons. Even though he was conversely lavished with praise, he still felt unappreciated due to sheer narcissism.

Both were entitled little children who were willing to resort to mass murder in order to feel better about themselves.

Hierophant wrote:

Alpharius/Omegon are possibly still loyal, or were manipulated into doing something they thought good.

Alpharius is still loyal
During the 'Alpharius vs Robute Gulliman' fight, he captured Gulliman and took his place, hence so little records about it
Then he swapped again when fulgrim went to kill gulliman
(Ok no one really knows but this is some mind-fu**ery right here)
The alpha legion put down more 'Just as Planned' than Tzeench!

Perturbed may be seen as arbitrarily cruel, but he does have a fair bit of logic behind him. The Iron Warriors as a legion were performing well before meeting their primarch, but not well enough. In a logical way, by decimation, he sacrificed that tenth of his men to strengthen the rest. It was through these early brutal practices that shaped the iron warriors into the fierce legion that would carry them through the war. We all know that the iron warriors hated the lot they drew in life, but there was little else that could be done because few other primarch were willing to make the tough calls.

commander dante wrote:

Hierophant wrote:

Alpharius/Omegon are possibly still loyal, or were manipulated into doing something they thought good.

Alpharius is still loyal
During the 'Alpharius vs Robute Gulliman' fight, he captured Gulliman and took his place, hence so little records about it
Then he swapped again when fulgrim went to kill gulliman
(Ok no one really knows but this is some mind-fu**ery right here)
The alpha legion put down more 'Just as Planned' than Tzeench!

This is based off d4chan's fan fiction, which based that part of a very old Index Astartes article about the Alpha Legion, which was meant to be hazy.

 Unyielding Hunger wrote:
Perturbed may be seen as arbitrarily cruel, but he does have a fair bit of logic behind him. The Iron Warriors as a legion were performing well before meeting their primarch, but not well enough. In a logical way, by decimation, he sacrificed that tenth of his men to strengthen the rest. It was through these early brutal practices that shaped the iron warriors into the fierce legion that would carry them through the war.

You're not very familiar with siege warfare are you? When besieging a defensive position, it's imperative to have numeral advantage over the defending force. By killing 1/10 of his own men, Perturabo basically reduced his legions effectiveness at performing siege warfare, and for no gain at that. Furthermore, many of those iron Warriors, who died in the culling, were distinguished soldiers. These were warriors, who even someone of such high standing as Guilliman, felt were worthy of considerable praise.

 ChazSexington wrote:

commander dante wrote:

Hierophant wrote:

Alpharius/Omegon are possibly still loyal, or were manipulated into doing something they thought good.

Alpharius is still loyal
During the 'Alpharius vs Robute Gulliman' fight, he captured Gulliman and took his place, hence so little records about it
Then he swapped again when fulgrim went to kill gulliman
(Ok no one really knows but this is some mind-fu**ery right here)
The alpha legion put down more 'Just as Planned' than Tzeench!

This is based off d4chan's fan fiction, which based that part of a very old Index Astartes article about the Alpha Legion, which was meant to be hazy.

Isnt every bit of Alpha Legion Information supposed to be hazy?

 Redcruisair wrote:

 Unyielding Hunger wrote:
Perturbed may be seen as arbitrarily cruel, but he does have a fair bit of logic behind him. The Iron Warriors as a legion were performing well before meeting their primarch, but not well enough. In a logical way, by decimation, he sacrificed that tenth of his men to strengthen the rest. It was through these early brutal practices that shaped the iron warriors into the fierce legion that would carry them through the war.

You're not very familiar with siege warfare are you? When besieging a defensive position, it's imperative to have numeral advantage over the defending force. By killing 1/10 of his own men, Perturabo basically reduced his legions effectiveness at performing siege warfare, and for no gain at that. Furthermore, many of those iron Warriors, who died in the culling, were distinguished soldiers. These were warriors, who even someone of such high standing as Guilliman, felt were worthy of considerable praise.

I am very familiar with siege warfare. Numbers mean nothing when you have the imperial army to take the casualties for you. That 10 percent had many veterans, and they were part of the problem. The remaining 90 percent learned the lesson, stepped up, and became even more effective. My point still stands. He tore them down and built them to what they should have been.

In Perturabo's case, I'd like to point out that he actually had some guilt after purging Olympia. And he joined Horus side as a form of redemption, seeing the latter's gift (Ferrus warhammer Worldbreaker) as the symbol of this forgiveness. Of course he also joined because the purging of his homeworld would cast the Imperium's wrath upon him, but that was not all. It actually a non-evil feeling that made him ironically turned completely traitor

 Unyielding Hunger wrote:
The remaining 90 percent learned the lesson, stepped up, and became even more effective. My point still stands. He tore them down and built them to what they should have been.

Did they actually learn a lesson and step up? I don't recall that part being mentioned but its been a while.

 Unyielding Hunger wrote:
I am very familiar with siege warfare. Numbers mean nothing when you have the imperial army to take the casualties for you.

So far, all depictions of the IW have them taking center stage in their seiges. To claim, that IW had "others" to take the casualties in the sieges, is to disregard all source material pointing towards the IW as being the ones to clearly suffer the most loses and hardship during the crusade. Hell, Perturabo's main complaint was, that he and his legion was the ones taking the heat in the sieges, and not the imperial army and the other legions.

 Unyielding Hunger wrote:
That 10 percent had many veterans, and they were part of the problem.

How so?

 Unyielding Hunger wrote:
The remaining 90 percent learned the lesson, stepped up, and became even more effective. My point still stands. He tore them down and built them to what they should have been.

Why did he tore them down? What was the need in that? Did he rebuild them because they had been performing poorly doing the great crusade?
No, IW did very well doing the great crusade, and they had many admires, including, but not limited to Guilliman and his Ultramarines.
Perturabo punished his legion because it was not the greatest one among all the legions.
This was an unreasonable expectation on Perturabo's part, especially so because they had to compete with other legions such as the Luna wolves and the Ultramarines, two mighty legions, who already had previously been reunited with their primarchs.

There was no logic behind Perturabo's decision to decimate his own legion. He was mad at the fact, that they hadn't been able to bring enough glory to his name, and thus he sought to remake the IW in the most extreme way possible.

Engrenages wrote:
In Perturabo's case, I'd like to point out that he actually had some guilt after purging Olympia. And he joined Horus side as a form of redemption, seeing the latter's gift (Ferrus warhammer Worldbreaker) as the symbol of this forgiveness. Of course he also joined because the purging of his homeworld would cast the Imperium's wrath upon him, but that was not all. It actually a non-evil feeling that made him ironically turned completely traitor

This actually makes him more evil.

Forgiveness is not Horus or Fulgrim's to give. That he accepted fake forgiveness rather than try to genuinely atone shows how little he actually cared about the people he killed, and how much he cared about his own ego and insecurities.

The symbol of forgiveness was a weapon given to him by his brother, that was stolen from the murdered corpse of another brother. Let that sink in a little...

You're feeling bad about yourself because your teachers are making you work hard and you don't have a lot of friends, so you go back to your school and shoot and kill everyone in it. You then start to feel bad about what you did, so ask your equally murderous friends for forgiveness. They tell you that you did nothing wrong, and hey, here, have this PS4 I took when I killed one of our mutual friends to make you feel better. If you'd read that in a news report, all you would see is evil, evil, evil.

That Perturabo sees this as a perfectly acceptable series of events shows how far off the rails he had gone. For someone who demanded perfection and logic in others, he was found wanting and behaved irrationally constantly. He was a hypocrite who chose to murder others rather than come to terms with his own double standards.

Peturabo was the wrong man for the job, and he knew it, he was a builder and engineer, but was forced to use those talents in siege warfare, as a by product of his upbringing when he got his legion he enacted decimation upon them, this does 2 things, enforces a kind of loyalty (badly) and serves to show the others that you are willing to sacrifice them to achieve a goal, this then encourages them to do the same, so from top to bottom every iron warrior knows to follow that order to storm.the breach, no matter the cost, this makes a very effective siege force and for a primarch to do something akin to this is not unusual.

Peturabo should have been given a job like guiliman or dorn, had he not been ostracised he would have remained loyal, try to imagine dorn and peturabo working together on the emperors palace, horus would have sharted himself at the mere thought of attacking that!

In Perturabo's defence he was raised by the tyrant of Lochos a man known for being shrewed and cunning even among the sea intrigue in his court. In fact one of the first things the tyrant does is put Perturabo as a boy to the test, having him face deadly and skilled warrior in hand to hand combat and faced with puzzles devised by the best scholars. Only after all of that was Perturabo "adopted" as the tyrants son, even after it could be said that Perty never returned any affection given to him as he knew knew that he was only viewed as a asset.

On the second note, from a young age Perturabo from his own accounts, was able to see the eye of terror clearly from where ever he was unless there was some intervening object
Even when he could not see it he could feel it "watching and judging" him. Considering the the eye is a the biggest gate in the galaxy to a realm of pure mind****ery, I have no doubt that chaos was working him over from also the very beginning, planting the seeds of paranoia, insecurity, and inadequacy.

If you actually look deeper into Perturabo's character he never wanted to be a conquerer as the emperor designed him but a architect of great and wonderous structures and a diplomat. When he builds a auditorium for Fulgrim, he feels fulfilled and almost at ease with himself. When Fulgrim is almost assassinated in said auditorium Perturabo is about as close to heart broken as we ever see him his great hall of entertainment and acoustics sullied by acts of war and violence.

Magnus was tricked by Tzeentch, not Horus. The Primordial Annihilator is an apparition/avatar/manifestation/underling of Tzeentch, and slowly nudges Magnus towards the plan - to destitute the loyalists from the Thousand Sons.

Magnus believes he's in control of the situation, but the Chaos plan was way bigger than just the TS - they were manipulating other events (especially with Kor Phaeron and Erebus) to the point Horus is wounded by the Nurgle-ish blade. It is there when Magnus notices a "disturbance in the force" and psychically tries to save Horus.

THIS is where Tzeench's plans regarding Magnus and the TS comes to fruition: Horus believes more in Erebus than in Magnus (and that happened because of his daddy issues - no way a well-minded Horus would hear more from a Chaplain than from a brother Primarch). As he realizes Horus is lost, Magnus tries to warn the Emperor the fastest way possible - via the Warp. When he meets resistance above Terra, he forces his way through and falls on the Emperor's secret labs, killing a lot of psykers with the psychic backlash and important people inside the lab. This was planned by Tzeentch to cut father and son.

With the orders to arrest Magnus, Leman Russ supposedly meets Horus and have his orders altered from imprisonment to execution. After having his entire planet destroyed and offered a deal by the Primordial Annihilator, Magnus had to choose the deal to don't lose his entire Legion to the Space Wolves.

Later, Magnus shows up (psychically) in a meeting with other betrayers Primarchs and he states he'll side with them - but between going to the Planet of the Sorcerers and this meeting, a long time passed and the betrayers had to convince him to join them. Magnus only did that to avenge his Legion and the people who lived in Prospero, not because he was tricked by Horus in doing that.

Magnus got pushed into a corner by Tzeentch until he had no choice, he hated Horus but the survival of his legion was at stake if the loyalists won

Mortarion was closer to Horus than the Emperor, Horus was able to convince Mortarion that the Emperor's dabbling in the warp and tyrannical tendencies were enough to rebel. It played on Mortarion's own trauma from his days on Barbarus

Perturabo was angry/jealous/spiteful

The books imply that besides Horus/fulgrim/lorgar most legions and primarchs didn't even know what chaos was.

In Betrayed Kharn and his men are confused and terrified by all the weird demon gak that starts popping up around ultramar, implying they had no idea what they were getting into.

Mortarion seems to have left out of pride, totally unaware of Nurgle's existence until typhus traps them in the warp.

Mortarion joined Horus because he despises tyrants, and felt that the Emperor was overstepping his authority as Emperor.

Perturabo joined Horus because he blew up his home planet, killing billions, and felt that only Horus would forgive him. He was also a general pariah among the Primarchs and felt under-appreciated.

Magnus joined Horus because his legion was being hunted to extinction by the Wolves.

None of them trusted Chaos or felt especially obligated to them. They were all ensnared by indirect means.

The Emperor betrayed Magnus by sending Wolves and keeping secrets.

This is pure speculation but others around Perturabo may have been under the impression that he suffered from delusions of persecution and hallucinations as he could always feel and/or see the Eye of Terror and it felt like it was constantly judging his every action with perhaps more than a little contempt. Due to this, Perturabo feels to me like a paranoid schizophrenic and he seems to be viewed as such by those who know about his "hallucination." He probably was quite relieved when Fulgrim confirmed that the Eye of Terror was indeed real and that he actually wasn't hallucinating. But it had to have taken a serious toll on him constantly seeing or feeling something that others said wasn't there but he was certain was real.

And having the feeling that he was merely an asset reinforced again and again couldn't have been good for said delusions of persecution.

Magnus sold his soul to tzeentch when Russ was burning prospero on Horus' comman/lie
Mortarion had a better relation ship with Horus than Big E, and sold his soul to Nurgle to save his legion from being killed by super space aids
Perturabo helped horus because he hated Dorn and being treated like crap, and being giving all the gak jobs.

The only one I'm not 100% sure about is Perturabo.

Simply put: Primarch-sized egos.

It's oft overlooked these days, but the reason Mortarion got stuck in the warp to begin the long temptation of Nurgle's Rot was because by that time he'd realized his mistake and was going to attack Horus' fleet as soon as they dropped back into real space.

Nurgle told Typhus about that, so Typhus killed the Navigators.

Magnus is the little Emperor though. He truly believes his poo doesn't stink and that he can do no wrong. He was completely sure that he controlled all powers of chaos and that it could never influence him. Anything that ever went wrong was "not his fault".

Perturabo just didn't like warfare. He didn't like his job and took it as a personal affront that he had to keep doing it. He wasn't as mistreated as he liked to think, he merely convinced himself of that. He didn't understand that there were other Primarchs who felt that way and that they were only acting out of a sense of duty. He was too stubborn to be anyone's friend enough to figure out it wasn't just him doing the hard jobs. Look no further than his praetorian guard for evidence. Even Angron had brothers in arms, Perturabo built robots.