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How do!

Yes I know what-ifs can be corny and lame. And no I can’t and won’t guarantee this one will be any different. But I can hope. And it’s exactly as the title says. But is also assuming such a conflict may have postponed the Heresy somewhat. Why? Well let me introduce you to my List Of Provisos. Or at least the ones I can perceive.

1. We’re talking the Great Crusade during or near its absolute zenith.
2. That means many of the galactic players of 40K just….aren’t in any shape to really play a role. Eldar are still reeling from The Fall. Orks have had a damned good kicking at Ullanor, destroying any kind of cohesion
3. Being unavoidably post-Ullanor, all the Primarchs have been united with their Legions.

Now…the sticky one. Would or wouldn’t The Emperor return to war to better lead his Sons and Legions against this new extra galactic menace? That I’ll leave to the individual to decide.

5. The Hive Fleets can produce any gribblies they can in 40K - so we’re assuming things like Tyrant Guard, Biovores and Zoanthropes were never adaptations gained by consuming Astartes, Orks and Eldar respectively, as speculated in the 3rd Ed Codex. This proviso is to avoid bogging down conversation.
6. We’ll see a similar if not outright identical invasion pattern of the Hive Fleets.

Those out the way? How do you think it might shake out?

My main thoughts is the Imperium could make a better hand of it, but not to the point the Hive Fleets are simply ROFLstomped. With few other foes of any existential threat at first, that’s a lot of men and materiel to be thrown at the Hive Fleets. And we know they’re especially vulnerable to space borne losses, as defeat in space not only reduces their number, but their feeding opportunities.

However. After Behemoth is dealt with (see proviso 6) multiple other Hive Fleets invade in rough unison. Which begins to present opportunity to the other species of the Galaxy. Not necessarily to “you were so busy over there we knacked Terra” opportunity, but enough to at least start bleeding Imperial Forces away from the threat and engagement against the Hive Fleets.

Would it prevent the sort of rebellion we saw in the Heresy? I honestly dunno. So I’ll let others kick that potential argument off.

I don't see the current amount of known hive fleets to be enough to put up any fight against the Imperium at its most powerful moment post Golden age.

In current 40k they are dangerous because Imperial forces are spread thin. They can hardly do any form of offensive and at the same time are still able to best or outright kill hive fleets without spending _that much_ ressources*.

So the current hive fleets against a united Imperium with all 18-20 Primarchs, their legions and led by the Emperor? No way.

It really depends on how many more Tyranids are "out there" outside of our galaxy.


*speaking on a galactic scale with a million worlds.

You could of course easily argue that Golden Age Imperial might would squash the gribblies flat without any issue.

However, let's remember the rascally speedy evolution of the Tyranids that makes them such a lovely scrap.

Let's say the first couple of tendrils get suitably curb stomped. The Hive Mind would change the game, the types of gribblies we would see I think would be different to their 40k versions if they are dealing with far more marines. More big brain type creatures would exist to try and combat the primarchs.

It's not an easy scenario to play out. The Tyranids aren't really like anything the Imperium has fought and while there are comparisons like with the Ullan-orks or Rangda, neither fits as a good show of what the Imperium would do as they were contained to specific areas of the galaxy and could be corralled more easily.

The issue with the Rangda is that in-universe the wars were so catastrophic that entire Legions worth of Astartes were killed (not specifically from any one Legion but in terms of casualties), Titan Legios destroyed, entire Expeditionary Fleets wiped out and hundreds of worlds were subject to Exterminatus with any survivors either sworn to secrecy or killed to prevent knowledge of the wars from spreading.
It is even theorised that one of the Lost Primarchs was killed during the Xenocides and it took the Emperor's personal involvement to end the 2nd Xenocide after 20 years of conflict.

Would the Imperium win these new Tyrannic Wars? Probably but the chances are the Imperial project would be damaged beyond repair.

Another concern? It only takes a single Genestealer getting lucky to implant a Primarch.

Now of course that doesn’t mean ‘suddenly super hybrids’, as we’ve nothing to suggest Primarchs ever procreated, or were (are?) even capable of that.

But a Primarch under the sway of a Broodmind could be a right spanner in the works as in terms of sheer authority and “everyone tends to do what I say” the taint could be be spread far and wide. Which for all we know is what happened to one of the Lost Primarchs.

We then have the Hive Mind’s very nature vs even Absolute Zenith Imperium’s far flung nature.

Sure any Hive Fleet engaged in space is going to have a pretty rough time of it. Not just because The Imperium of that era could handily churn out new ships and equipment, but with Astartes to spare, the surprisingly reliable “board it by whatever means and liquidate its organs” tactic could be done enmasse, ramping up Hive Fleet losses.

We’d also be looking at those filthy, banned weapons The Emperor liked to stockpile probably being deployed - though whether those are replaceable, I’d need to read more Heresy to properly comment.

My final thought is just how rapidly new Astartes could be recruited, equipped and shipped out. Not just equipped with their arms and armour, but warp capable craft. Same with the Solar Auxilia and Imperial Army. Because in a perverse way? When fighting Tyranids, your casualties only really work against you if the Hive Fleet or Tendril survives.

Tell a lie, this is my final thought. The Shadow in the Warp is of course a significant concern. Could The Emperor BS a work around? Something to allow relief fleets to pile into a contested system? Because that’s a major benefit of the Tyranids. If you can’t defeat them with the forces at hand when they arrive, it’s bloody difficult if not outright impossible to send in reinforcements.

The Stealer line of thinking only works if a Primarch could even be infected by one which seems massively unlikely.

And yes the Emperor has so many vaults filled with "DO NOT TOUCH" toys, then Vulkan, Ferrus, and Perturabo made some just for kicks as well. Then there's Xana to worry about with their cavalcade of insanity.

I don’t see why a Primarch couldn’t be infected? They have a genetic code to corrupt, and brains to come under the sway of a Broodmind.

Whether their legendary strength of will would be a help there we can of course only speculate.

I think the big reason why is because they're not fully biological beings but basically part warp-stuff to begin with, and given that genestealers wouldn't realistically be able to give the genestealer's kiss to a daemon prince, which is the closest equivalent to what a primarch is, I doubt it would have much affect, if any on a primarch. Especially considering that we have seen marines who have been infected by genestealers and they haven't immediately succumbed. The Scythes of the Emperor were able to resist the psychic call of the Hive Mind with a little help, I assume that Primarchs would have little difficulty given their physiology and mental fortitude are leagues above regular marines.

I feel the bigger concern would be when the Hive Mind would consume a Primarch because I could see them creating a genetic phage to target the specific gene-seed line of marines along the lines of the Blight that the Emperor's Children suffered but on a much worse and faster scale.

The Scythes were never infected, their human serfs were. Some Initiates were inevitably selected but IIRC none ever got far enough before the Cult among the humans was discovered and eradicated.

An Astartes can still be paralysed by a Broodlord's psychic abilities but getting infected with the Curse doesn't turn them into Hybrids as Astartes biology naturally rejects the infection (though it kills them in the process).

Just thinking weapons.

The Hive Fleets would, at least to begin with, have the same weapons they have now. That might seem arbitrary at first glance, but this is based on how they develop new weapon beasts. Until they’ve encountered something that’s causing a problem, they can’t counter it. Certainly I’m under the impression there’s not a lot of prediction going on, only reaction.

Which could make the existence of decent numbers of Phosphex and Volkite a problem for them. Both would be pretty adept in Heresy Numbers against hordes of Gaunt type creatures.

Another factor? With much higher numbers of Astartes present in fleets, the Hive Fleets might also have a rougher time boarding Imperial Ships. Their gribblies would of course be no less deadly, but Astartes are pretty handy in such actions. This I would say necessarily increases the number of critters you need to get onboard for a successful action.

Overall, at this possibly early stage in the conversation? I’m leaning toward it being a long, drawn out war, with a united Imperium being a tricky foe for the Hive Fleets to overcome.

If we could allow for the Shadow In The Warp to be countered or worked around? The Hive Fleets probably wouldn’t survive it, as they’d struggle to meaningfully replace losses incurred.

And whilst making Ramilese Class star forts would still be a significant effort? Smaller scale and enmasse just as handy in a scrap orbital defences might be proof against lone Hive Ships stumbling across a buffet and replacing on the quiet.

The galaxy is simply way too big for a concentrated force like the Great Crusade to fight Hive Fleets even if we assume the GC wins each and every fight.

400-200 billions of stars, billions of inhabitated worlds, a lot of potential food and space for a mere 2 million Space Marines to patrol.

 Tyran wrote:
The galaxy is simply way too big for a concentrated force like the Great Crusade to fight Hive Fleets even if we assume the GC wins each and every fight.

400-200 billions of stars, billions of inhabitated worlds, a lot of potential food and space for a mere 2 million Space Marines to patrol.

And the Mechanicum, Imperial Army, Titan Legions, Legio Custodes, Knight Houses, and Sisters of Silence all of which were present in far greater numbers than during the 40k timeline with often fancier and more warcrimey weapons *cough*Mechanicum*cough*

 Gert wrote:

 Tyran wrote:
The galaxy is simply way too big for a concentrated force like the Great Crusade to fight Hive Fleets even if we assume the GC wins each and every fight.

400-200 billions of stars, billions of inhabitated worlds, a lot of potential food and space for a mere 2 million Space Marines to patrol.

And the Mechanicum, Imperial Army, Titan Legions, Legio Custodes, Knight Houses, and Sisters of Silence all of which were present in far greater numbers than during the 40k timeline

Where they? from what I remember most of the Great Crusade was supported mostly by Terra and Mars, most of the IoM wasn't taxed/tithed and Horus joked doing so would break the Imperium.

‘One world cannot support and maintain such a gigantic undertaking singlehanded,’ she explained to the Warmaster in slightly over-shrill tones. ‘Terra cannot shoulder this burden alone. We are masters of a thousand worlds now, a thousand thousand. The Imperium must begin to support itself.’

‘Many worlds are barely in compliance, lady,’ Horus said gently. ‘They are recovering from the damage of war, rebuilding, reforming. Taxation is a blight they do not need.’

When she had retired from the room with her staff, Horus sat back, alone amongst his inner circle. ‘I have often thought,’ he remarked, ‘that it might be the eldar who unseat us. Though fading, they are the most ingenious creatures, and if any could over-master mankind and break our Imperium apart, it would likely be them. At other times, I have fancied that it would be the green-skins. No end of numbers and no end of brute strength, but now, friends, I am certain it will be our own tax collectors who will do us in.’

-Horus Rising

As for better and fancier weapons, yes and no as the IoM has developed newer weapons since then, that's basically the lore explanation of all the gear Loyalist Space Marines get that Chaos Space Marines do not.

Not every world was forced into compliance though. Indeed a good number welcomed the safety and reconnection offered by the growing Imperium, and provided armies to support the Great Crusade.

Some were patterned and trained in the proven method of the Solar Auxilia. Others were kind of their own thing.

Tyranids, once the true scale of the issue is known? They’re an extinction level event waiting to happen. That in itself is a strong argument to make some sacrifices and tighten belts, because either The Imperium stands as one with all hands to the pump? Or you face being devoured piecemeal.

 Tyran wrote:
Where they? from what I remember most of the Great Crusade was supported mostly by Terra and Mars, most of the IoM wasn't taxed/tithed and Horus joked doing so would break the Imperium.

In the initial stages pushing out of Sol sure, but by the time of Ullanor, the armed forces of the Imperium were colossal and the support network was far more effective and powerful.

The earliest years of the Crusade were also dominated by non-Astartes forces because there weren't enough Astartes to go round but just because the Legions grew, doesn't mean everything else stagnated. The more worlds that joined the Imperium, the more soldiers were raised to unite humanity. Forge Worlds reconnected with their Martian kin and were pumping out entire Titan Legions during the Crusade. Knight Worlds pledged their loyalty to the Emperor or Mars and were gifted with the technology to return their mounts to their former prowess.
Very few of the Expeditionary Fleets were even commanded by Astartes, it's just the more notable ones that we see in stories that play more pivotal roles.

The problem with Horus Rising is that it's the first step in a series that massively outstripped the original ideas and can be very inconsistent even between the first three books in the series.

As for better and fancier weapons, yes and no as the IoM has developed newer weapons since then, that's basically the lore explanation of all the gear Loyalist Space Marines get that Chaos Space Marines do not.

Newer doesn't mean better. The likes of the Thunderhawk, Leman Russ, and Indomitus Terminator armour are all lesser versions of other options that were commonplace during the Crusade.
The Russ is actually a perfect example as the Imperium needed a cheaper-to-produce tank for mortal forces as demand outstripped supply of the venerable and superior Malcador chassis. There were literally too many soldiers to keep producing the better option without having the Russ.

The Imperium was able to produce the likes of Gloriana Battleships, Volkite, Phosphex, and Rad weapons with relative ease to the point where entire platoons of Solar Auxilia would deploy with Volkite weaponry. Enire Chapters worth of Astartes were equipped with the most warcrimey of weapons available, just because they needed to be used quite a lot.
That's gone for the Tyrannic War era Imperium.

Also worth noting the cheaper/less intensive replacements were by no means bad, just easier/cheaper to produce and maintain when deployed in such significant numbers.

And the fancier versions were still being produced, and not necessarily in fewer numbers.

thinking about Emp gives me the thought: Tyranids are drawn to earth because the golden throne because it acts as a psychic beacon. but in an era without it, would the tyranids then be drawn to Emp? or would they lack any such central point to gather towards?

Well, the Astronomion exists during the Great Crusade, doing the same job. And we know that was able to remain active even when The Emperor was abroad in the Galaxy?


Automatically Appended Next Post:
I’m now wondering if or how the Hive Mind could adapt to things like Rad and Volkite Weapons.

Both are energy and radiation based (is there a scientific difference?), and particularly for Volkite the description doesn’t suggest there’s much left over except ash.

Yet in 40K, we have at least one example of energy weapons being adapted against, when Gaunts became highly resilient against Tau Pulse Weapons, which are essentially low yield Plasma weapons.

I would say the difference is that energy weapons like lasers and masers rely on conversion of beam energy into heat in the target.

Ionising radiation weapons (x-ray, gamma and neutron bombs) rely on damaging molecular bonds, disrupting DNA operations and apparently disrupting neural, nerve impulse and gastro-intestinal actions. The various clever gubbinz that make the body function just don't work any more.

 StudentOfEtherium wrote:
thinking about Emp gives me the thought: Tyranids are drawn to earth because the golden throne because it acts as a psychic beacon. but in an era without it, would the tyranids then be drawn to Emp? or would they lack any such central point to gather towards?

It's theorized that the Tyranids are drawn to it, however thus far their major tendrils have not reached for Earth but key other worlds - striking at homeworlds of Space Marine chapters.

I think the biggest problem with theory crafting anything along these fronts is we have no clue how big the Tyranid threat really is. We have no idea of their total size at all.

The Tendrils could be major fleets and each loss is a massive blow. They could be little more than exploratory fleets and their loss has no impact on the Swarm at all.



The biggest boons that the Crusade era Imperials have are unity and a lack of major opposing large=scale forces outside from the Tyranids. Humanity conquered a huge swathe of the Galaxy with blood, effort, but also a bit of a power vacuum. So in theory they would have utterly smashed the current Tendrils that the Tyranids have sent in the 40K setting. How the Tyranids would adapt to that is honestly unknown. They could do everything from pulling back to find another Galaxy; to holding ground; to going all out with an invasion force that dwarfs the current fleets that have been seen.

They might have become even more surgical. It could even be that they simply wait it out. 10thousand years is nothing to a race that moves between Galaxies. So who knows perhaps they DID appear in the 30K era; decided to wait and the 40K era has enough chaos and weakness that they feel its prime time to strike.

On that last point? I’ve previously speculated it is possible Hive Fleets have previously penetrated the galaxy. But, due to the power of the dominant species at those times, they were handily defeated.

Consider that at the height of their respective powers, the Old Ones, Necrons and Eldar could create and destroy Suns, or scour entire worlds of life.

Yet for just the reason you mentioned, intergalactic, non-warp Travel, the Tyranids must be patient, sending in tendrils now and again to test the waters. Like us deciding a bowl of soup fresh out the pot needs to cool for a minute before we can eat it without scalding ourselves.

Which raises the question of whether that indeed did happen. We know a great number of Xenos species were rendered extinct by the Great Crusade, who’s to truly say a Hive Tendril wasn’t among them, with the wider Hive Mind realising it was just a bit too spicy in terms of risk/reward.

The galaxy being empty is also a boon for the Tyranids, in particular the lack of Chaos (which is basically a rival predator) and Necrons that throw around weaponry that makes even The Great Crusade's fancy wargear look like a joke.

I’d argue it’s the very lack of such Other Threats that poses the biggest threat to the Hive Fleets.

Even in modern 40K, The Imperium can just about, kind of, not disastrously, counter the Tyranid threat - or at least put up sufficient fight to slow them down and bag the odd staggering win.

My concern for the early Imperium is that post Behemoth, there are enough Hive Fleets that the Eldar and Orks could find enough breathing space to become new fronts. Perhaps not sufficient to truly threaten The Imperium, but enough to be an ongoing problem that needs to be countered.

Eldar could, potentially, be negotiated with to some degree. Orks? Yeah that’s just not a good idea ever. And given their losses at Ullanor, it seems you couldn’t do a Kryptman, as there just wasn’t enough Orks in on place at the same time. Well….not yet, anyways.

Orks might in fact be the biggest wild card. We know they’re naturally drawn to the biggest punch ups, and so they could be a boon or a problem when engaging Hive Fleets, as they’re unlikely to pick a particular side - but stand to give a hypothetically beleaguered Hive Fleet so much needed biomass.

 Mad Doc Grotsnik wrote:

I’m now wondering if or how the Hive Mind could adapt to things like Rad and Volkite Weapons.

Both are energy and radiation based (is there a scientific difference?), and particularly for Volkite the description doesn’t suggest there’s much left over except ash.

Yet in 40K, we have at least one example of energy weapons being adapted against, when Gaunts became highly resilient against Tau Pulse Weapons, which are essentially low yield Plasma weapons.

I mean aren't the Malstrain supposed to be heavily irradiated? Maybe the prominence of those types of weapons would work in the favour of the Imperials.

 Mad Doc Grotsnik wrote:
On that last point? I’ve previously speculated it is possible Hive Fleets have previously penetrated the galaxy. But, due to the power of the dominant species at those times, they were handily defeated.

Another aspect is that we don't really know the true limits of the Tyranids. There's a world they are "building" steadily which has a purpose we have no idea about save that right now its projects a huge "shadow in the warp".

Tyranids strike me as efficient in that they evolve for what they encounter. It's a similar to how Orks will generally become as powerful as needed to beat whatever is around and will then collapse into in-fighting.
So it might be that if the Tyranids came on the scene much earlier; they might well have evolved down different pathways. Against the Eldar I could see them developing more down the Norn Queen line - super powerful elite units instead of vast swarms. Why strike with a vast swarm that gets blown apart when they destroy a planet; when you can infiltrate and threaten them with insanely powerful single combatants.

Also lets not forget world-blowing-up works both ways. Even the Imperium in 40K can scour a world of all life*. But its a delaying tactic not a defeating one. It would work against most factions, but against a force that comes from outside the Galaxy and who are operating with unknown (possibly limitless) numbers; destroying worlds is just a delay tactic. It's not a path toward victory.


*at least almost, spores from orks are known to sometimes survive


Automatically Appended Next Post:

 Olthannon wrote:

 Mad Doc Grotsnik wrote:

I’m now wondering if or how the Hive Mind could adapt to things like Rad and Volkite Weapons.

Both are energy and radiation based (is there a scientific difference?), and particularly for Volkite the description doesn’t suggest there’s much left over except ash.

Yet in 40K, we have at least one example of energy weapons being adapted against, when Gaunts became highly resilient against Tau Pulse Weapons, which are essentially low yield Plasma weapons.

I mean aren't the Malstrain supposed to be heavily irradiated? Maybe the prominence of those types of weapons would work in the favour of the Imperials.

Malstrain are genetically altered by deliberate design.

Chances are with all the radiation in space as it is, the Tyranids are more than effective at evolving counters to irradiated worlds and weapons. The weakness with Malstrain is that it happened over a very short timeframe against captive Tyranids. There was no chance for them to evolve a counter.

 Mad Doc Grotsnik wrote:
I’m now wondering if or how the Hive Mind could adapt to things like Rad and Volkite Weapons.

Both are energy and radiation based (is there a scientific difference?), and particularly for Volkite the description doesn’t suggest there’s much left over except ash.

Yet in 40K, we have at least one example of energy weapons being adapted against, when Gaunts became highly resilient against Tau Pulse Weapons, which are essentially low yield Plasma weapons.

There's a big difference between the Hive ships being resistant to background radiation found in space, and a Hive Tyrant getting shot in the face by an Irrad-Cleanser.

I think more is being made of Tyranid's hyperadaptability than the reality of it. If the Tyranids were so hyperadaptive to different weapons then Gaunts would now be immune to the likes of Bolters and Lasguns surely? But they aren't. The hyperadaptability is not played out across the entire race but is piecemeal. A larger bioform might not be susceptible to a Volkite Charger but then it's not really susceptible to a Bolter either and like Bolt weapons, Volkite weapons scale upwards in terms of output.

If Gaunts can reliably be put down by Lasguns and Autoguns, I don't see why the Imperium would need to worry about Tyranids adapting to the likes of Rad, Phospex or Volkite weapons en-masse.

On the Malstrain? It’s a bit of both, so far as I’m aware. Which as I’m yet to get my three, sorry, two hands on the latest Necromunda fluff is limited.

But, it seems there’s some kind of genetic wonk, compounded and further effed with by the exotic weapons used to flatten and crush Hive Secundus. What Warhammer Community has said is the resultant strain whilst stilldeadly, are lesser versions of Purestrains as we know them - and more importantly? The Hive Mind wants nothing to do with them.

On scouring of worlds? It absolutely does matter, depending on just what you did.

The Hive Fleets seem to rely on massive “and now we eat everything on the plant/system” to replace and rebuild its own forces.

That’s what the Kryptman Gambit centred on. First accept you probably couldn’t successfully defend all those worlds. So instead, you plant your bombs/deleters, give the Hive Fleets at least what-two if not what-for, then retreat, setting off the bombs/deleters, denying the Hive Fleets their lunch and reward. And so you slowly bleed and starve the Hive Fleets. You deny them any chance to gain significant enough biomass to replace their inevitable and hopefully substantial losses.

Now of course we come to the question of just how numerous are the Hive Fleets? On background maps we’re shown Purple Arrows of significant galactic scale. But….that only really shows confirmed contact, but not density.

If they did show density? The galaxy is of course completely shafted.

the thing people always seem to forget about the Tyranids is that they have the galaxy surrounded. You have hive fleets Leviathan and Hydra coming from below to the southwest, Behemoth, Gorgon and Kraken coming from galactic southeast and Jormungandr, Moloch coming from galactic northeast. It's a pincer movement and one that means they can strike anywhere they like in the galaxy because guess what? Space isn't 2D

The fact they're coming from below means they can hit any world with almost no resistance because the entire Imperium and all the milky way races operate along the galactic plane. It doesn't matter how many dead worlds you put "in front" of a hive fleet when they can just come up from underneath, it's like building walls and trenches when your opponent has orbital weapons

Great crusade era imperial forces certainly stand a better chance of holding them off for longer but every single tyranid ever encountered so far has been the tiniest exploratory tendril of a force of incomprehensible size, and when it hits a couple more active primarchs won't be able to stand against enough bodies to drown every planet in the galaxy all at once. The galaxy is doomed, it's just a matter of how long people can survive before that doom hits

Charax wrote:

The fact they're coming from below means they can hit any world with almost no resistance because the entire Imperium and all the milky way races operate along the galactic plane. It doesn't matter how many dead worlds you put "in front" of a hive fleet when they can just come up from underneath, it's like building walls and trenches when your opponent has orbital weapons

On the other hand, a hive fleet coming from above or below is just as likely to blunder into a heavily defended area where it will be immediately noticed. It's not unreasonable to guess that hive fleets that approached from the edges of the galactic disc first found largely feral worlds, and used those for biomass to build up strength. As a result, they got to the size that they are before they faced any sort of opposition that could hurt them. A hive fleet that drops into the middle of a heavily populated sector just stirred up a literal hornets nest, and will quickly get an emergency response from the Imperium (or whoever is in charge in that region). It will likely be stomped on hard before it has an opportunity to gain more than a minimal foothold. And as a result, the hive fleet won't have the opportunity to build up before it is forced to start facing heavy opposition.

When hive fleet attacked Macragge it was defended by the Ultramarines Chapter. Imagine if it was defended by the Ultramarines Legion.