The Imperium Secundus Arc: Waste of Great Potential

[b1soul]

Feel like this could've been a really cool arc...but it ended up being a bunch of inconsequential primarch battles and rather pointless diversion.

 

I think the arc needed a villain other than Curze. It should've been turned into a campaign w/ WE, WB, and NL involved

[ZebraM]

It's really weird how the Imperium Secundus arc almost completely neglected the Word Bearers and World Eaters, even though they should really be the Ultramarines biggest concern.

[b1soul]

I was thinking...

 

If you're gonna make this a big deal...turn it into a large sub-campaign

 

BA, UM, DA vs. WB, WE, NL

 

Have WB and WE stick around instead of leaving early on

[Apothecary Vaddon]

still might be a lot of stories to be told in the arc, but I'd imagine they'd be reserved for shorts. 

[Lucien Eilam]

It's really weird how the Imperium Secundus arc almost completely neglected the Word Bearers and World Eaters, even though they should really be the Ultramarines biggest concern.

 

The Word Bearers and World Eaters are gone. They withdrew from Ultramar after Angron's ascension, off to rejoin Horus. Imperium Secundus is founded after those events.

[Praetor of Calth]

With the recent news from Convention Secundus suggesting we literally have two books to go until the end of the arc, well one now with the release of Pharos. It feels like we've had this huge buildup which resulted in very little.

 

I actually think a choice of a second big "villian" is a very good idea. There are still a massive amount of Word Bearers and World Eaters tearing :cuss up across Ultramar, yet we've seen very little of this. That being said I wouldn't want to see Lorgar and Angron being the secondary main villans, I feel like the confrontation between Lorgar and Guilliman brought the arc between the two to a close. I don't feel like any continuation of that arc could produce anything of value to the series at this point.

 

In my eyes, if wasn't for all the superspy stuff we've been forced to endure throughout the series, the Alpha Legion would have been the perfect second big villian to introduce into Imperium Secundus. I.S is effectively founded upon misinformation, or rather a lack of, this is something the Alpha Legion excels at. I think it would have been incredible to see the AL launch a massive misinformation campaign, killing anyone, traitor or loyalist alike, that might threaten the one thing that keeps I.S alive. The idea that the Emperor is dead. That's something that actually fits with the original idea with the Alpha Legion, rather than the whole superspy stuff we have now.

 

I also feel like we should have seen a book each to show how each of the three loyalist primarchs were effected by the founding of the new Imperium. By the looks of things we'll see one about The Lion, but I want a book showing how the Codex. Astartes came about (Yes I know we've had snippets) or how Sanguinius dealt with being Emperor.

 

The potential and ideas are there, the content covering them isn't.

[Kriegsmacht]

I am in agreement with the OP. It would have been fine if it was the Ultramarines but it felt more like they shoehorned the other legions because they couldn't have the Blood Angels and the Dark Angels(with the Space Wolves) race back to Terra with the new stretched timeline. Like they were suppose to in the original storyline.

[ZebraM]

In my eyes, if wasn't for all the superspy stuff we've been forced to endure throughout the series, the Alpha Legion would have been the perfect second big villian to introduce into Imperium Secundus. I.S is effectively founded upon misinformation, or rather a lack of, this is something the Alpha Legion excels at. I think it would have been incredible to see the AL launch a massive misinformation campaign, killing anyone, traitor or loyalist alike, that might threaten the one thing that keeps I.S alive. The idea that the Emperor is dead. That's something that actually fits with the original idea with the Alpha Legion, rather than the whole superspy stuff we have now.

 

It would of been interesting to see the Alpha Legion fostering rebellion within the 500 Worlds and then Guilliman having to deal with said rebellions. It'd also help fester the hatred between the two primarchs.

[Praetor of Calth]

 

In my eyes, if wasn't for all the superspy stuff we've been forced to endure throughout the series, the Alpha Legion would have been the perfect second big villian to introduce into Imperium Secundus. I.S is effectively founded upon misinformation, or rather a lack of, this is something the Alpha Legion excels at. I think it would have been incredible to see the AL launch a massive misinformation campaign, killing anyone, traitor or loyalist alike, that might threaten the one thing that keeps I.S alive. The idea that the Emperor is dead. That's something that actually fits with the original idea with the Alpha Legion, rather than the whole superspy stuff we have now.

 

It would of been interesting to see the Alpha Legion fostering rebellion within the 500 Worlds and then Guilliman having to deal with said rebellions. It'd also help fester the hatred between the two primarchs.

It certinally would have done, I think the best way to have done this story wise, would have been to have one of the Loyalists discover this "secret" after defeating the AL in battle. I'd fit it in in this sort of direction;

 

Unremembered Empire- End of the AoD arc, start of I.S.

 

War Without End Anthology- (Laurel of Defiance, Safe and Shadowed Place etc)

 

Deathfire- The Salamanders take Vulkan back to Nocturne

 

Rules of Engagement- Thiel and Guilliman form the Codex Astartes.

 

Dreadwing- The Lion follows his own secret agenda on the far reaches of Ultramar.

 

Virtues of the Sons- The I.S lies ablaze, Sanguinius stands as regent, his brothers follow their own agendas. Unable to leave Ultramar, Sanguinius must rely on the virtues of his sons.

 

Pharos- The Night Lords attack the Pharos beacon.

 

The Serpent Beneath- The UM search for the DA in the far reaches of Ultramar, where they are ambushed by the Alpha Legion. Upon combating them they uncover a grave secret. The Emperor lives and Terra still stands.

 

Nightfall- The loyalists regroup at Macragge preparing to head back to Terra. Sanguinius orders the Pharos beacon to be pointed towards Terra, which will leave Ultramar divided. While schism rifts through the loyalist camp. A massive Night Lords fleet descends on Macragge, intent on recovering their primarch.

[ZebraM]

Yeah that would of been much better. It would of also made things like the attempted assassination of Guilliman by Alpha Legion marines dressed as Ultramarines have actual cause and effect within the storyline, rather than a random occurrence.

[b1soul]

 

The Word Bearers and World Eaters are gone. They withdrew from Ultramar after Angron's ascension, off to rejoin Horus. Imperium Secundus is founded after those events.

They should have stayed for the sake of a better story

[b1soul]

In my eyes, if wasn't for all the superspy stuff we've been forced to endure throughout the series, the Alpha Legion would have been the perfect second big villian to introduce into Imperium Secundus. I.S is effectively founded upon misinformation, or rather a lack of, this is something the Alpha Legion excels at. I think it would have been incredible to see the AL launch a massive misinformation campaign, killing anyone, traitor or loyalist alike, that might threaten the one thing that keeps I.S alive. The idea that the Emperor is dead. That's something that actually fits with the original idea with the Alpha Legion, rather than the whole superspy stuff we have now.

Mate...this is just brilliant. Perhaps Alpharius himself could be involved. Maintaining the Imperium Secundus' erroneous belief that father is dead...perfect job for the AL.

 

Instead we're getting all this silly Curze business.

[Phoebus]

The only real problem I have with the Imperium Secundus story arc is, well, the Imperium Secundus part.

Lorgar's Ruinstorm was a great way to explain the rather awkward way the XIII Legion had been absent from everything post-Calth in the older lore. Know No Fear was a great way to start the story off. Betrayer really showed just how much the Five Hundred Worlds suffered in that dark time between Isstvan V and the Siege of Terra. The Pharos, the Shattered Legions, the Blood Angels, and the Lion coming to Macragge? All also very good ideas.

The Word Bearers and the World Eaters leaving is likewise no big issue. They did what they came to do. Lorgar wanted revenge, a ritual that would fuel his cause while crippling Ultramar, and a way to remake Angron - not necessarily in that order. Angron wanted to break stuff and, eventually, gain vengeance for his tragic treatment in Nuceria. All those goals were met.

But honestly, that whole angle about having to set up an Imperium because the loyalists trapped by the Ruinstorm had no way of knowing that Horus hand't sacked Terra is such a reach.

Look, first of all, "Imperium Secundus" was a fancy way of rebranding what was left of the Five Hundred Worlds. That's it. As far as Ultramar being the continuation of the Imperium and carrying on the flame of Humanity... it was doing that by default, whether Guilliman had to declare it or not. As far as the legitimacy of his experiment, there was absolutely nothing to be gained by rebranding Ultramar into Imperium Secundus... unless you were a publishing house looking to bestow a name upon a story arc within a larger series you were publishing. The people of Ultramar knew who their lord was. Whether Terra was sacked or not, their loyalty to Guilliman and his ideals wasn't going to change.

Beyond that, if Horus did manage to sack Terra and kill the Emperor, it's not like the Five Hundred Worlds are going to stop him from finishing his bid for galactic domination. Where loyalists are concerned, it's not like there was any question as to who actually ruled that realm. Is there some Theoretical wherein some older loyalist Primarch might show up and claim that his "seniority" over Guilliman gives him legitimate claim over Ultramar? I suppose... but then, Guilliman was apparently so selfless and pragmatic that he was willing to let either of the two Primarchs who actually did make it to Macragge sit on his contingency throne as a figurehead regent/Emperor. Aside from those, Guilliman didn't know whether the Khan was loyal or not, but could reasonably surmise he wouldn't be interested in vying for leadership of a realm. Guilliman must also have known that Corax and Vulkan couldn't challenge him (their legions were shattered).

That leaves Leman Russ and Rogal Dorn.

Of those two, Dorn was found earlier, is cited as being right up there with Horus in the early novels, and clearly enjoyed the Emperor's confidence (serving as his praetorian). I think it's fair to say that if Guilliman was willing to accommodate the Lion in his schemes, he'd certainly have room for Dorn. Where Russ is concerned, there's a legitimate reason to worry that the Vlka Fenryka might have clashed with the Ultramarines... but (A) that's still not reason enough for an Imperium Secundus... and ( nothing would be more likely to provoke such a fight from them THAN a declaration of Imperium Secundus.

All that just makes it such a thematic headache for me. A very valid premise for a storyline is made needlessly complicated with a political twist that doesn't do anything to further the plot. Take away the pointless pomp and circumstance and hand-wringing over setting up regents or what have you, and you still have the potential to tell strong stories about marooned legions itching to get back into the greater fight.

Speaking for myself, I only saw one angle likely to keep "Imperium Secundus" interesting: the Lion's advertised intent to bring the pain to Guilliman in the event that he, too, was guilty of treason. That chance evaporated before the end of The Unremembered Empire, though. Such is life!

[veterannoob]

I hope to finish it today so I'm not reading the second half of this page yet but I did see Convention Secundus mentioned and was wondering what that was about so I can grab my notes from CS;)

 

Stupid work blocking my reading time :(

[Legatus]

Lorgar's Ruinstorm was a great way to explain the rather awkward way the XIII Legion had been absent from everything post-Calth in the older lore. 

 

In the older lore, Calth had been attacked at the same time when the rest of the traitors were attacking Terra, so it wasn't all that awkward. Also, the traitors had moved from Istvaan V directly to Terra, and hadn't hung around for seven years.

[Kelborn]

At the beginning I thought that the whole heresy line would be like:

-one book for each legion to introduce the most important characters and to show, what happened to them during the heresy, which occure about the same time

-a couple of books to get an overview

 

But now we have 7 years, filled with all kind of ideas the authors came along, like the IS :/

[Phoebus]

 

Lorgar's Ruinstorm was a great way to explain the rather awkward way the XIII Legion had been absent from everything post-Calth in the older lore. 

 

In the older lore, Calth had been attacked at the same time when the rest of the traitors were attacking Terra, so it wasn't all that awkward. Also, the traitors had moved from Istvaan V directly to Terra, and hadn't hung around for seven years.

On the one hand, we have the old Ultramarines lore, which, for a good while, advertised that the Ultramarines really didn't have much of a role in the Horus Heresy.

 

From the old Ultramarines Index Astartes article:

 

 

When Horus turned against the Emperor and led the galaxy into the most destructive civil war it had ever seen, the Ultramarines were engaged deep in the galactic south. Their very successes had carried them far from Horus' armies in the north-east and Guilliman did not receive word of the betrayal until the battle for Terra was under way. Gathering his Legion, Guilliman led his forces towards Terra, en route destroying a rebel fleet on its way to reinforce Horus. The war had been won by the time Guilliman's warriors reached Terra, but the Imperium was in turmoil.

From the old Codex: Ultramarines:

 

 

Whilst the Horus Heresy plunged the Imperium into savagery and civil war, the Ultramarines were engaged on the southern edge of the galaxy. Their very success had carried them far from Earth and isolated them from the conquering armies of Horus in the north-east. News of Horus's treachery did not even reach the Ultramarines until the attack on Earth was underway.

 

And then, on the other hand, we have the old Word Bearers lore, which advertised that the Ultramarines had, in fact, been embroiled in a rather massive campaign that only culminated (as opposed to kicking off) with the Battle of Calth.

 

From the old Word Bearers Index Astartes article:

 

 

When the Heresy erupted and the shackles of loyalty were cast off, the Word Bearers set upon the Sons of Ultramar with unbridled hatred. The Ultramarines were initially stunned, and Lorgar was able to push them back to Ultramar, the region of space that the Ultramarines govern and defend. It was upon the world of Calth that the final battle would take place.

Like I said, awkward. Sure, the "default setting" of early Imperial history is "knowledge corrupted and/or altered to the point that it resembles mythology", but the fact remains that the early lore had almost opposite perspectives for the Ultramarines and the Word Bearers. To me, that's awkward. To you, maybe not. To each their own.

 

Beyond that, it's not like the Traitors have been "hanging around" for a seven-year period. The Forgeworld books do a better job (in my humble opinion) of qualifying this, but the newest lore shows how the Siege of Terra needed to be preceded by a comprehensive conquest of the Imperium. Again, this is just my perspective, but regardless of how new the seven year period is, only the most unrealistically literal reading of the old lore (which typically summarized the whole of the Heresy in two-three paragraphs) would have one presume that Horus simply marched from Isstvan to Terra with no significant stops inbetween.

[Marshal Rohr]

 

 

 

 

Lorgar's Ruinstorm was a great way to explain the rather awkward way the XIII Legion had been absent from everything post-Calth in the older lore.

In the older lore, Calth had been attacked at the same time when the rest of the traitors were attacking Terra, so it wasn't all that awkward. Also, the traitors had moved from Istvaan V directly to Terra, and hadn't hung around for seven years.

On the one hand, we have the old Ultramarines lore, which, for a good while, advertised that the Ultramarines really didn't have much of a role in the Horus Heresy.

 

From the old Ultramarines Index Astartes article:

When Horus turned against the Emperor and led the galaxy into the most destructive civil war it had ever seen, the Ultramarines were engaged deep in the galactic south. Their very successes had carried them far from Horus' armies in the north-east and Guilliman did not receive word of the betrayal until the battle for Terra was under way. Gathering his Legion, Guilliman led his forces towards Terra, en route destroying a rebel fleet on its way to reinforce Horus. The war had been won by the time Guilliman's warriors reached Terra, but the Imperium was in turmoil.

From the old Codex: Ultramarines:

Whilst the Horus Heresy plunged the Imperium into savagery and civil war, the Ultramarines were engaged on the southern edge of the galaxy. Their very success had carried them far from Earth and isolated them from the conquering armies of Horus in the north-east. News of Horus's treachery did not even reach the Ultramarines until the attack on Earth was underway.

And then, on the other hand, we have the old Word Bearers lore, which advertised that the Ultramarines had, in fact, been embroiled in a rather massive campaign that only culminated (as opposed to kicking off) with the Battle of Calth.

 

From the old Word Bearers Index Astartes article:

When the Heresy erupted and the shackles of loyalty were cast off, the Word Bearers set upon the Sons of Ultramar with unbridled hatred. The Ultramarines were initially stunned, and Lorgar was able to push them back to Ultramar, the region of space that the Ultramarines govern and defend. It was upon the world of Calth that the final battle would take place.

Like I said, awkward. Sure, the "default setting" of early Imperial history is "knowledge corrupted and/or altered to the point that it resembles mythology", but the fact remains that the early lore had almost opposite perspectives for the Ultramarines and the Word Bearers. To me, that's awkward. To you, maybe not. To each their own.

 

Beyond that, it's not like the Traitors have been "hanging around" for a seven-year period. The Forgeworld books do a better job (in my humble opinion) of qualifying this, but the newest lore shows how the Siege of Terra needed to be preceded by a comprehensive conquest of the Imperium. Again, this is just my perspective, but regardless of how new the seven year period is, only the most unrealistically literal reading of the old lore (which typically summarized the whole of the Heresy in two-three paragraphs) would have one presume that Horus simply marched from Isstvan to Terra with no significant stops inbetween.

2nd edition lore fight!

[b1soul]

I like how they've made the Horus Heresy a methodical campaign of conquest and consolidation by the Traitors rather than simply a rushed decapitating strike.

 

It makes sense. Black Library just doesn't have enough talented authours to do such an epic campaign justice.

[Mantras]

 

 

Lorgar's Ruinstorm was a great way to explain the rather awkward way the XIII Legion had been absent from everything post-Calth in the older lore. 

 

In the older lore, Calth had been attacked at the same time when the rest of the traitors were attacking Terra, so it wasn't all that awkward. Also, the traitors had moved from Istvaan V directly to Terra, and hadn't hung around for seven years.

On the one hand, we have the old Ultramarines lore, which, for a good while, advertised that the Ultramarines really didn't have much of a role in the Horus Heresy.

 

From the old Ultramarines Index Astartes article:

 

 

When Horus turned against the Emperor and led the galaxy into the most destructive civil war it had ever seen, the Ultramarines were engaged deep in the galactic south. Their very successes had carried them far from Horus' armies in the north-east and Guilliman did not receive word of the betrayal until the battle for Terra was under way. Gathering his Legion, Guilliman led his forces towards Terra, en route destroying a rebel fleet on its way to reinforce Horus. The war had been won by the time Guilliman's warriors reached Terra, but the Imperium was in turmoil.

From the old Codex: Ultramarines:

 

 

Whilst the Horus Heresy plunged the Imperium into savagery and civil war, the Ultramarines were engaged on the southern edge of the galaxy. Their very success had carried them far from Earth and isolated them from the conquering armies of Horus in the north-east. News of Horus's treachery did not even reach the Ultramarines until the attack on Earth was underway.

 

And then, on the other hand, we have the old Word Bearers lore, which advertised that the Ultramarines had, in fact, been embroiled in a rather massive campaign that only culminated (as opposed to kicking off) with the Battle of Calth.

 

From the old Word Bearers Index Astartes article:

 

 

When the Heresy erupted and the shackles of loyalty were cast off, the Word Bearers set upon the Sons of Ultramar with unbridled hatred. The Ultramarines were initially stunned, and Lorgar was able to push them back to Ultramar, the region of space that the Ultramarines govern and defend. It was upon the world of Calth that the final battle would take place.

Like I said, awkward. Sure, the "default setting" of early Imperial history is "knowledge corrupted and/or altered to the point that it resembles mythology", but the fact remains that the early lore had almost opposite perspectives for the Ultramarines and the Word Bearers. To me, that's awkward. To you, maybe not. To each their own.

 

Beyond that, it's not like the Traitors have been "hanging around" for a seven-year period. The Forgeworld books do a better job (in my humble opinion) of qualifying this, but the newest lore shows how the Siege of Terra needed to be preceded by a comprehensive conquest of the Imperium. Again, this is just my perspective, but regardless of how new the seven year period is, only the most unrealistically literal reading of the old lore (which typically summarized the whole of the Heresy in two-three paragraphs) would have one presume that Horus simply marched from Isstvan to Terra with no significant stops inbetween.

 

 

 

To be fair, given I.S was founded on the premise the war on Terra had already finished, this isn't too far off. I personally like the idea of IS as it has fleshed out the UM's hugely, but its niave to think that huge aspects of the HH that happened are not remember in 40k. So much stuff about the traitors was "forgotten", IS is as much heresy as what Horus did IMO, but its never been mentioned in 40k that the Blood Angels/UM/ and Dark Angels set up their own little empire

[Phoebus]

I get what the premise of Imperium Secundus is; my whole point is that I don't think it's a very good one.

[Legatus]

In the original lore, as soon as Horus attacked Istvaan III and proclaimed his opposition to the Emperor, all over the galaxy governours and commanders rose up to side with Horus, and the galaxy wide Heresy began. After several months of galaxy wide civil war, and after long hesitation on the Emperor's part, then months of preparation to attack Horus, seven Legions attacked Istvaan V. With four more Legions siding with Horus and three loyal Legions destroyed, Horus then moved against Terra. In their confrontation, Horus is killed and the Emperor mortally wounded. The traitors retreat from terra, but fighting between traitors and loyalists continues for a further seven ears until the traitors have been banished into the Eye of Terror.

 

That is not just "Second Editio lore", since that course of events was still described in the Collected Visions artbooks. While the Horus Heresy indeed lasted over seven years, the attack on Terra happened very early on, and the remaining seven years were a struggle to chase out the traitors and restore order. In earlier editions, that entire conflict was called the "Horus Heresy". However, in later editions, the period after the battle for Terra was called "the Scouring", while the initial stage was more commonly referred to as the "Horus Heresy".

 

In that story, the Ultramarines do enter events very early on, but still only at the moment when Horus moves against Terra. It's just that this also happened early on in the campaign. If only those early stages are referred to as "the Horus Heresy", then the Ultramarines would get involved only at the very end, to then be involved prominently throughout the subsequent "Scouring" stage.

 

This story would have allowed for a few months of traitr/loyalist encounters in the wider region around the Istvaan System, as Horus' followers support uprising rebels. The traitor Legions then consolidate at Istvaan V when the loyalists attack. Then there is the battle for Terra (while the Word Bearers move against Ultramar), and then seven more years of traitor vs. loyalist action. While it may be a bit anti-climactic that Horus is already dead at this stage, so is the Emperor (effectively), and the Imperium is similarly leaderless at this point. While the traitors no longer follow a single leader, the Imperium struggles to maintain order and to establish a new governing body. The traitors also still have nine battleworn Legions at their disposal, the loyalists have five battered Legions and one fresh (and over-strength) with the Ultramarines.

 

 

With the new BL plot line, they added a gap ov several years between the loyalist attack on Istvaan V and the traitor attack on Terra. The Ultramarines do not enter play at the end of that gap (attack on Terra), but at the beginning. So now they have to have something to do during those years. And thus we have the "Imperium Secundus" plot line, which amonted to nothing and means the Ultramarines sat around and twiddled their thumbs while the Imperium burned (instead of crusading in ignorance). The three Legions taken out at Istvaan V not only miss the battle for Terra and then get a chance to rebuild during the scouring, they were taken out at the beginning of several years of "Horus Heresy". But I guess it's ok, the Ultramarines didn't do anything either. A lack of action seems to be the ordinary.

[Half Goat]

In my opinion the concept that the initial HH from horus turning to battle of terra spanning months, upto a year, is ludicrous when you take into account the as distances between forces and communication and how long each conflict would take to complete. I like the idea it has been stretched out spanning several years which reflects the reality of coordinating a military campaign so complex

[Legatus]

It is consistent with a universe where 300 Marines can cripple an average planetary military within a week (see 3rd Edition Codex Space Marines), or where 200,000 Marines (or even 2,000,000 in BL) can conquer around a million worlds witin 200 years. 

 

Obviously Horus would have covertly prepared his coup in advance, securing the allegiances of certain important worlds. After Istvaan III, it did take the loyalists a good few months to mount a response. And that was probably a bit rushed, since they did send the Night Lords, but were unable to reach the Ultramarines or Dark Angels. During those months Horus' forces could have secured important jump routes and figured out how possible get to Terra. And with three loyal Legions destroyed at Istvaan V and three other Legions (DA, SW, UM) too far away, what better moment to make the move on Terra?

 

It doesn't take 7 years to get from Istvaan to Terra. And with the Imperium in a state of civil war, the traitor forces do not have to fight through countless Imperial blockades to get there. There would be enough routes claimed by the traitors, or even just contested ones that would not put up much resistance. Especially if Horus (with help of the Alpha Legion) had secured a route in advance of Istvaan III or in the months before the loyalists made a move on Istvaan V. Horus wasn't just slowly spreading the rebellion from Istvaan outwards. He had planted the seed of corruption in countless worlds in advance. Some worlds turned simply because they felt more aligned with the charistmatic warlord that liberated their world, rather than with the distant regent figure they were told about.

 

It's not implausibel at all. It's just anti-climactic, that's all. Horus and the Emperor duelling early on, and then seven more years of fighting with the Imperium in ruins.

[Phoebus]

Legatus,

 

There are two aspects to this discussion: the aspects of the timeline itself, and subjective opinions on what constitutes a "good" timeline.

 

In the original lore, as soon as Horus attacked Istvaan III and proclaimed his opposition to the Emperor, all over the galaxy governours and commanders rose up to side with Horus, and the galaxy wide Heresy began. After several months of galaxy wide civil war, and after long hesitation on the Emperor's part, then months of preparation to attack Horus, seven Legions attacked Istvaan V. With four more Legions siding with Horus and three loyal Legions destroyed, Horus then moved against Terra. In their confrontation, Horus is killed and the Emperor mortally wounded. ...

 

That is not just "Second Editio lore", since that course of events was still described in the Collected Visions artbooks.

 

Alan Merrett himself pointed out in the Collected Visions that the Horus Heresy finds its origins in a "small snippet of text" originally published in Chapter Approved - The Book of the Astronomican. I've never been able to spot that blurb, but I'll take his word for it!

 

In the older lore that followed (e.g., Codex: Ultramarines, Codex: Angels of Death, the Index Astartes articles), the Horus Heresy was summed up in a few paragraphs. There was no real timeline (that I'm aware of) - in terms of months, years, etc. - that indicated how long that conflict lasted. The closest thing I know is the Index Astartes article on the Codex Astartes, which briefly stated that "[The gods of Chaos] would strike and crush the Emperor with one swift blow. When rebellion erupted, Horus led more than half of the Space Marine Legions into the bloodiest civil war to engulf the galaxy and laid siege to the Emperor's palace."

 

Then we had the Collected Visions. I don't dispute that they present a condensed, months-long timeline. I do argue, however, that any attempt to condense a conflict the scale of the Horus Heresy into a matter of months is doomed to be awkward and poorly designed at best. I was disappointed that this is what such a key person in the development of the 40K IP was able to come up with.

 

Still, as Alan himself subsequently offered, the Horus Heresy was "embellished" and "added to" ever long before the soon-to-be-decade-old Horus Heresy series even started. Speaking purely for myself, if the price of a more sensible timeline is to present new lore, such as the Ruinstorm (and whatever else keeps the loyal Legions from getting back to Terra), then so be it.

 

While the Horus Heresy indeed lasted over seven years, ...

Can you remind me where that is stated? I'm almost positive it's not in Collected Visions; those books make references to "many months" passing between, e.g., Isstvan III and Isstvan V, and between Isstvan V and the Siege of Terra.The seven-year bit has to be somewhere, though. I don't think the Black Library team arbitrarily picked that number.

 

The traitors retreat from terra, but fighting between traitors and loyalists continues ... until the traitors have been banished into the Eye of Terror. ... the attack on Terra happened very early on, and the remaining seven years were a struggle to chase out the traitors and restore order. In earlier editions, that entire conflict was called the "Horus Heresy". However, in later editions, the period after the battle for Terra was called "the Scouring", while the initial stage was more commonly referred to as the "Horus Heresy".

Even within the Collected Visions, the Heresy is distinct from the Scouring. Within that book's "Aftermath" chapter, the wars of The Scouring are described as distinct from the Heresy. The same is true for the Index Astartes series of articles, whether by way of narrative or by describing these periods in separate sections. 
 

In that story, the Ultramarines do enter events very early on, but still only at the moment when Horus moves against Terra. It's just that this also happened early on in the campaign. If only those early stages are referred to as "the Horus Heresy", then the Ultramarines would get involved only at the very end, to then be involved prominently throughout the subsequent "Scouring" stage.

More precisely, in the Collected Visions books Horus sent Lorgar to attack Calth after the culling of the Loyalists on Isstvan III and before the Dropsite Massacre on Isstvan V (as show on page 158). Thus, either way, the Ultramarines are involved at the very beginning. They eventually rally, overcome Lorgar's treacherous blow, and finally launch for Terra right around the climax of the Siege.

 

While it may be a bit anti-climactic ...

This is purely my opinion, but yeah, any timeline that tries to define the Heresy as several years of "aftermath" preceded by mere months of the main action strikes me as anti-climactic, at best. 

 

So now they have to have something to do during those years. And thus we have the "Imperium Secundus" plot line, which amonted to nothing and means the Ultramarines sat around and twiddled their thumbs while the Imperium burned (instead of crusading in ignorance).

That's not entirely fair, though, is it? Black Library haven't had the Ultramarines "sitting around" by any stretch of the phrase. The Battle of Calth was followed by an extended war for that world. This was part of a larger effort that sought to fight off the Shadow Crusade waged by Lorgar and Angron. Subsequently, we have the events of Pharos, which bring the Night Lords into the mix. I have no idea what the future holds for Imperium Secundus, but I think it's obvious that the Ultramarines will either be shown having a hand in the greater conflict that is the Heresy - or their efforts will be alluded to (much like when we first catch up with the Lion, post-Fallen Angels, "Savage Weapons" simply mentions the two years of fighting between the Dark Angels and the Night Lords during the Thramas Crusade).

 

 

It is consistent with a universe where 300 Marines can cripple an average planetary military within a week (see 3rd Edition Codex Space Marines), or where 200,000 Marines (or even 2,000,000 in BL) can conquer around a million worlds witin 200 years.

If anything, this is another area where the newer lore has helped the setting make more sense. One of the first things Dan Abnett's Horus Rising helped with is in qualifying that there are more than four thousand primary expedition fleets operating at the closing years of the Great Crusade. Given two centuries and somewhat advantageous Warp transit, I would hope that close to a million worlds could be conquered by so great a force.  

 

As to what three hundred Space Marines can do, or what smaller and greater numbers are capable of (see: Know No Fear by Dan Abnett and Horus Heresy: Betrayal), it's always a good idea for any of us to inject our own dose of realism by remembering that any independent Legiones Astartes force arrives with warships capable of demolishing entire cities with a salvo from their weapons. Those same weapons would go a long way toward evening the odds against a numerically superior foe.

 

 

It doesn't take 7 years to get from Istvaan to Terra.

No, but it would take a long time to fight all the way to Terra. The disappointing thing about the old timeline was that there was so much handwaving involved. You literally have to assume, as you offered, that in the span of time between Davin and Isstvan III, Horus Lupercal and his fellow primarchs bribed, intimidated, manipulated, or sweet-talked whoever they needed to in order to secure an essentially instantaneous route to Terra.

 

 

It's not implausibel at all. It's just anti-climactic, that's all.

And if we were talking about a historical conflict, this would be all well and good. There would be no point, after all, in griping about how Hannibal convinced a number of cities ostensibly allied to Rome to more or less let him have his way and maneuver throughout Italy as needed.

 

This isn't a historical record, though. It's a fictional setting, based on which products ranging from novels to miniatures are sold for profit. So yeah, a primary consideration should be to create a rich, engaging, dramatic, and - to the extent possible - plausible storyline. With that in mind, front-loading the conflict before the climactic Siege of Terra makes all the sense in the world. Placing 6/7 of the Horus Heresy after the death of the demigod it was named, during a period that essentially serves as little more than an extended denouement, on the other hand?