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 Mad Doc Grotsnik wrote:

 Dekskull wrote:
Haha I like how a thread about lore turns into a thread about why its pointless to think about this stuff too much.

Greatest example of inconsistent narrative. I buy the 3rd edition rule book. On the back it says humnaity is on the verge of extinction...then I open it up and I'm like. "Wait a minute, the emperor conquered like the entire galaxy...there are trillions of humans? How is that verge of extinction?"

If the governance of The Imperium falls, it’s all over. Clunky and barely working as it is, it still manages to get its fighting forces where they’re needed, most of the time.

Take that organisation away? It’s every world for itself, and back to the Age of Strife. You’d be looking at mass starvation of Hive Worlds, as imports of food would be imperilled or outright halted. Lose those worlds, and a chunk of your recruitment goes with it, not to mention manufacturing of goods (even just Lasguns and other basic essentials).

There’s also the question of exactly how Kyn, Eldar and Tau would ally. One could argue Kyn would be interested in trade deals - except they have those with The Imperium. Those aren’t levels of trade you can easily replicate elsewhere.

I do think there's potential for isolated pockets of the imperium to form smaller, better-coordinated, more self-sufficient factions. The mix of planet types and warp routes would have to be just right, and the transition period would be rough, but the end result could be a relatively agile, organized human faction that would lack the massive scale of the imperium but slightly make up for it by not being as prone to supply chain disruption, distant millitary assets with conflicting objectives, etc. Sort of like the worlds near Ultramar.

Such a faction would probably get wiped out in the long-term, but they could serve as a sort of "second wind" for a disrupted imperium.

The sector is already the largest real practical Imperial unit of organization. Though there is inter-sector trade and the tithes to the Imperium, most sectors seem to be pretty self-contained. The Gothic Sector for example as shown in the BFG rulebook survived decades on its own effectively cut off from the Imperium.

That is what I would think would happen in Imperium Nihilus. Individual sectors would go their own way and secure their own interests in the absence of any coordination or dictates from Terra. They might share a shared heritage in Imperial culture (at least among the ruling class), but they would be effectively separate political entities and de facto independent. Frankly I think it would be a good thing as it would give a background reason for all the Imperial vs. Imperial games without the tired excuse of "training exercises".

The only real impact of being part of the imperium is the tithe, the black ships and the required treaties with admech and marines.


Remove the imperium from a sector and they keep all their extra guard troops, whatever materials they provide as their tithe and don't lose their psykers.


It would only be a problem if they don't have permanent admech installations/worlds to maintain technology, or for some reason the sector doesn't have representation for everything needed for all planets to survive. I'd find it hard to believe a sector would require other sectors' imports to survive though.

Otherwise they're already self-sufficient and they'd even have more troops to protect their holdings and more materials to support themselves.

 Hellebore wrote:
The only real impact of being part of the imperium is the tithe, the black ships and the required treaties with admech and marines.


Remove the imperium from a sector and they keep all their extra guard troops, whatever materials they provide as their tithe and don't lose their psykers.


It would only be a problem if they don't have permanent admech installations/worlds to maintain technology, or for some reason the sector doesn't have representation for everything needed for all planets to survive. I'd find it hard to believe a sector would require other sectors' imports to survive though.

Otherwise they're already self-sufficient and they'd even have more troops to protect their holdings and more materials to support themselves.

I think the main difference would be when you get a really large scale threat in the isolated sector. If a massive waaagh or hive fleet tendril is headed your way, there's a chance that the imperium will see it coming and deem you important enough to send a huge pile of reinforcements your way (or even take the fight to the next sector over before it reaches you). So while you might be better able to leverage the extra troops currently in your sector, you might not be quite as well equipped to deal with the jumbo-sized threats that the imperium is actually slightly effective at dealing with.

Also take the Imperium away and you lose the subtle elements too. The Inquisitors who root out cults and other undesirables. Take away the Imperium and you could find yourself losing your entire sector to a Genestealer Cult uprising; or suddenly wake up to realise that your advisor is a Chaos Demon and you've just sacrificed your entire sector to a Chaos God and now you're putting some armour on to go fight the Imperium.

 Hellebore wrote:
The only real impact of being part of the imperium is the tithe, the black ships and the required treaties with admech and marines.


Remove the imperium from a sector and they keep all their extra guard troops, whatever materials they provide as their tithe and don't lose their psykers.


It would only be a problem if they don't have permanent admech installations/worlds to maintain technology, or for some reason the sector doesn't have representation for everything needed for all planets to survive. I'd find it hard to believe a sector would require other sectors' imports to survive though.

Otherwise they're already self-sufficient and they'd even have more troops to protect their holdings and more materials to support themselves.

I disagree entirely.

Any IG regiments raised are typically deployed off-world. That largely leaves you with your PDF, which lack the same range of equipment on offer to all IG Regiments. If your system doesn’t have a particularly developed industrial base? Your arming options are going to be extremely limited.

You’d also struggle to keep your space lanes safe, as outside of System Defence Monitors? You won’t have Naval assets. Sure the assets you do have should be enough to deter opportunistic raids. But as soon as a more substantial threat comes a-knocking? You’re stuffed.

We also need to consider how The Imperium is organised right now. Typically worlds tend to be quite dedicated in role and purpose. A Hive World cannot feed its massive population itself, and so relies on imported food stuffs. An agri-world by comparison tends to have a dramatically lower population. The lower the population, the smaller the native PDF. This in itself causes a problem should raiders decide to setup shop.

And not every system has its own Hive World, Agri-World etc. Even if it does, you still need a means to move your armed forces around. In various Cain novels, such craft are sort-of press ganged into service by The Imperial Guard, as they otherwise belong to private individuals, particularly warp capable ones. Lose The Imperium, and you may struggle to get your hands on such craft. That in turn can leave worlds of lower population extremely vulnerable as sure you may have a PSF numbering in the millions on your Hive World, but with no way to get them deployed to an Agri-World, they might as well not exist.

Lose your Agri-World, and starvation is gonna come soon.

The Imperium works because it’s so large. The Imperial Guard may be, head for head, largely unimpressive. But they can bring truly staggering numbers into the fray. And unless we’re talking a conflict the likes of Armageddon, where Orks actively seek to join in ensuring both sides have or need a constant influx of warriors? Those overwhelming numbers are usually plenty to see off a threat.

This in turn is why certain forces are threats. Tyranids, Eldar, Chaos, Orks and Necrons don’t rely on The Warp in the same way The Imperium and others do. Chaos in particular can exert varying levels of control and influence, quieting Warp Storms to allow passage, or forcing one to spring up in their wake, either delaying or preventing Imperial intervention.

I think of The Imperium as something akin to Wolverine. It’s various foes can inflict enough damage to limit its options, as it’s healing factor keeps up. Should one of those sources of damage be dealt with? It might be able to go properly on the offensive, crushing each other foe in turn. But for now, it’s mostly tied up replacing losses. No sooner is one theatre concluded, than another springs up and its off to war yet again.

If anyone wants to truly defeat The Imperium? It needs to be a colossal blow. One to drive it fully to its knees, and with a sustained follow up to stop it getting back to its feet. Abaddon came close with the fall of Cadia and the opening of the great rift. Yet…The Imperium was able to weather it, and is now organising to strike back.

Most forces are held at a sector level though, and cross-sector deployments of Imperial Guard or Imperial Navy are rare and typically reserved for major wars or crusades. Some planets produce exceptionally high numbers of guard forces within their regular tithe, so these would probably produce a sector surplus of regiments that could be sent elsewhere by the Departmento Munitorum, but this will be rare.

The rank of Warmaster/Lord Solar specifically exists to coordinate the military resources from more than one sector, and this is a special, temporary position that requires High Lord of Terra authorisation. The highest "ordinary" military ranks are based at a sector level, with ranks above this being administrative over Segmenta or representing the organisation within the Imperial Senate on Terra (and frequently a member of the High Lords).

As such, a typical sector has independent force generation able to deal with most threats excepting the truly apocalyptic like massive Waaaaghs or Tyranid hive fleets. The only thing they would likely lack is the support of major Forge Worlds- most sectors do not have a major world of this kind, so high-end equipment would be an irreplaceable resource if the sector became independent. Things like battleships, titans, super heavy tanks, rare guns like laser destroyers.

But we’re not talking Sectors. We’re talking planetary systems.

The kin would have no part in this.

1 they don't need to, there already well entrenched in the imperal athority,

2 why would they whant to overthrow a good customer. (even if the customer dosn't know they are)

3 It's a bit gakky sabing famly in the back. even if you don't like them. and the empire is kin wither they like it or not.

 Mad Doc Grotsnik wrote:
But we’re not talking Sectors. We’re talking planetary systems.

Almost all the replies on this page above your post, including the one you quoted, referenced sectors, as the effective largest unit of Imperial control for most practical situations.

Morty_Jhones wrote:
The kin would have no part in this.

1 they don't need to, there already well entrenched in the imperal athority,

2 why would they whant to overthrow a good customer. (even if the customer dosn't know they are)

3 It's a bit gakky sabing famly in the back. even if you don't like them. and the empire is kin wither they like it or not.

It would be a W40k novel, so some very creative brain would have an idea of a demon infested chaos dwarf who sows the seed of discord. BAM -- They want to wage war against their most sinister enemy, the Imperium.

 Mad Doc Grotsnik wrote:

 Hellebore wrote:
The only real impact of being part of the imperium is the tithe, the black ships and the required treaties with admech and marines.


Remove the imperium from a sector and they keep all their extra guard troops, whatever materials they provide as their tithe and don't lose their psykers.


It would only be a problem if they don't have permanent admech installations/worlds to maintain technology, or for some reason the sector doesn't have representation for everything needed for all planets to survive. I'd find it hard to believe a sector would require other sectors' imports to survive though.

Otherwise they're already self-sufficient and they'd even have more troops to protect their holdings and more materials to support themselves.

I disagree entirely.

Any IG regiments raised are typically deployed off-world. That largely leaves you with your PDF, which lack the same range of equipment on offer to all IG Regiments. If your system doesn’t have a particularly developed industrial base? Your arming options are going to be extremely limited.

You’d also struggle to keep your space lanes safe, as outside of System Defence Monitors? You won’t have Naval assets. Sure the assets you do have should be enough to deter opportunistic raids. But as soon as a more substantial threat comes a-knocking? You’re stuffed.

We also need to consider how The Imperium is organised right now. Typically worlds tend to be quite dedicated in role and purpose. A Hive World cannot feed its massive population itself, and so relies on imported food stuffs. An agri-world by comparison tends to have a dramatically lower population. The lower the population, the smaller the native PDF. This in itself causes a problem should raiders decide to setup shop.

And not every system has its own Hive World, Agri-World etc. Even if it does, you still need a means to move your armed forces around. In various Cain novels, such craft are sort-of press ganged into service by The Imperial Guard, as they otherwise belong to private individuals, particularly warp capable ones. Lose The Imperium, and you may struggle to get your hands on such craft. That in turn can leave worlds of lower population extremely vulnerable as sure you may have a PSF numbering in the millions on your Hive World, but with no way to get them deployed to an Agri-World, they might as well not exist.

Lose your Agri-World, and starvation is gonna come soon.

The Imperium works because it’s so large. The Imperial Guard may be, head for head, largely unimpressive. But they can bring truly staggering numbers into the fray. And unless we’re talking a conflict the likes of Armageddon, where Orks actively seek to join in ensuring both sides have or need a constant influx of warriors? Those overwhelming numbers are usually plenty to see off a threat.

This in turn is why certain forces are threats. Tyranids, Eldar, Chaos, Orks and Necrons don’t rely on The Warp in the same way The Imperium and others do. Chaos in particular can exert varying levels of control and influence, quieting Warp Storms to allow passage, or forcing one to spring up in their wake, either delaying or preventing Imperial intervention.

I think of The Imperium as something akin to Wolverine. It’s various foes can inflict enough damage to limit its options, as it’s healing factor keeps up. Should one of those sources of damage be dealt with? It might be able to go properly on the offensive, crushing each other foe in turn. But for now, it’s mostly tied up replacing losses. No sooner is one theatre concluded, than another springs up and its off to war yet again.

If anyone wants to truly defeat The Imperium? It needs to be a colossal blow. One to drive it fully to its knees, and with a sustained follow up to stop it getting back to its feet. Abaddon came close with the fall of Cadia and the opening of the great rift. Yet…The Imperium was able to weather it, and is now organising to strike back.

How reliable is the imperium in deploying 'state' assets to sectors though? Most sectors are on their own all the time, with reinforcements arriving some time after invasions occur.

The segmentum battlefleets are not limitless and they are on constant patrol, so the chance that they're in any one sector within the segmentum isn't huge.


From the perspective of a huge invasion/war of attrition sure a sector is in trouble. But despite the OTT nature of 40k, most invasions and wars aren't sector ending events, they're raids and border clashes. The 3rd war for armageddon isn't the norm for conflicts but the exception.

So, statistically, it is unlikely that a sector will have any problems without the potential for imperial support in the form of 'state' forces being deployed. And as I said, if the imperium isn't taking guardsmen anymore, those regiments stay within their sector to defend it. And that becomes less of a problem if they're allied to ajoining sectors for mutual defence.

But my point that a sector by itself is already effectively isolated and autonomous anyway, within the greater imperium, still stands.

Independent sectors keeping their own psykers is a disadvantage considering Terra maintains a near-monopoly on psychic training- by and large sectors would have to resort to simply murdering any psykers to prevent warp disasters if they didn't fall to Chaos.

 Hellebore wrote:



How reliable is the imperium in deploying 'state' assets to sectors though? Most sectors are on their own all the time, with reinforcements arriving some time after invasions occur.

The segmentum battlefleets are not limitless and they are on constant patrol, so the chance that they're in any one sector within the segmentum isn't huge.


From the perspective of a huge invasion/war of attrition sure a sector is in trouble. But despite the OTT nature of 40k, most invasions and wars aren't sector ending events, they're raids and border clashes. The 3rd war for armageddon isn't the norm for conflicts but the exception.

So, statistically, it is unlikely that a sector will have any problems without the potential for imperial support in the form of 'state' forces being deployed. And as I said, if the imperium isn't taking guardsmen anymore, those regiments stay within their sector to defend it. And that becomes less of a problem if they're allied to ajoining sectors for mutual defence.

But my point that a sector by itself is already effectively isolated and autonomous anyway, within the greater imperium, still stands.

Most Imperial Guard raised in a sector stay in that sector anyway, so I doubt many sectors would gain much military strength for separating from the wider Imperium unless they included some of the worlds that export unusually large numbers of troops, like Krieg or (formally) Cadia, but they lose the opportunity to receive out-of-sector support and the rare equipment from major forge worlds. An independent sector is still likely to be a formidable space empire in its own right, of course, but I don't think it is militarily stronger for going alone.

If you take a look at which human empires survived and indeed thrived in the Long Night, it was the ones that were based around many sectors and planetary systems that proved able to tough it out. The Interex and Diasporex are two big ones that even combined their holdings with those of likeminded Xenos species.
Some systems and sectors might have managed alone but the vast majority were ruled by Xenos, powerful Psyker overlords or were simple eradicated.

 Wyldhunt wrote:
I do think there's potential for isolated pockets of the imperium to form smaller, better-coordinated, more self-sufficient factions. The mix of planet types and warp routes would have to be just right, and the transition period would be rough, but the end result could be a relatively agile, organized human faction that would lack the massive scale of the imperium but slightly make up for it by not being as prone to supply chain disruption, distant millitary assets with conflicting objectives, etc. Sort of like the worlds near Ultramar.

These factions wouldn't have anything like Astronomican, though (so no safe space travel, even ignoring issue of pirates and daemons), no soul binding required to make safe psykers, so no space internet either, no black ships or inquisition - there might be a local equivalent but it would much less resources to deal with bigger threats. Assuming such a faction would have allied SM/Admech/navigators it could theoretically last a bit but it would need to dump all the backwardness and start innovating (easier said than done) and couldn't do anything about big ork/chaos/tyranid invasion.

Huron tried to make such human faction out of Maelstrom, and despite having some of the best techmarines in the Imperium, willingness to innovate whole new tactical and strategic doctrine, alliances with aliens and renegade humans, pocket SM legion loyal to him, and other advantages, he was toppled by relatively small Imperial incursion. You wouldn't even need Ghaz or one of Daemon primarch to topple one of these, even smaller warband or waaagh would do.

 Hellebore wrote:
Remove the imperium from a sector and they keep all their extra guard troops, whatever materials they provide as their tithe and don't lose their psykers.

Can you say 'daemon invasion'? Because that's how you get one

And keeping a handful of regiments is all cool and well, but Imperium acts like insurance - you put a little in, only to get a crusade in return when things went FUBAR and you really need it. What happens in RL with people who have no insurance but something bad happens? Oh yes, they go bankrupt...

 Irbis wrote:
And keeping a handful of regiments is all cool and well, but Imperium acts like insurance - you put a little in, only to get a crusade in return when things went FUBAR and you really need it. What happens in RL with people who have no insurance but something bad happens? Oh yes, they go bankrupt...

That's the idea, sure. In practice... Well, how lucky is your sector?

Asenion wrote:
Pretty self explanatory. Could they ?

No. But they could certainly make sure that they all (and the Imperium) lose. That's not a good game of chicken to play in the face of Chaos, Orks, Necrons and Tyranids.

 JNAProductions wrote:
That's the idea, sure. In practice... Well, how lucky is your sector?

Imperium wouldn't last 10.000 years if they were bad at it. Did Armageddon fall after being targeted by biggest ork attack in millennia? Macragge after being attacked by entire hive fleet? Any of 12 Black Crusades that were beaten back each time? No matter the scale of the threat, Imperium beat it back each time, you just need to see what any of the above do to the space outside of the Imperial protection (total extermination, invariably) to see why staying out is bad idea even in early M41, never mind M42.

People hype up sector sized factions like Interex and Diasporex while conveniently 'forgetting' both were wiped out offscreen by a tiny portion of Space Marine legion, so their ability to stand up to even small scale threat is virtually zero. Especially if it's something that will easily outnumber you, a few extra PDF regiments notwithstanding (orks, daemons, tyranids, etc, etc).

The Interex were not beaten by a "tiny" portion of a Legion. It was the core of the Luna Wolves led by Horus himself alongside the rest of the 63rd Expeditionary Fleet which included a large contingent from the Legio Mortis. The Interex was also more technologically advanced than the Imperium, though not as warlike, and had weapons capable of breaching power armour with relative ease.
Likewise the Iron Hands led by Manus struggled to beat the Diasporex as the coalition was deft at naval warfare. They had to call upon the Emperor's Children to help them conduct raids and damage vital interstellar infrastructure to draw out the Diasporex fleets.
As for the Imperium, every victory is a pyrrhic one, especially the Black Crusades. The cost is always felt and each successive Crusade was harder to put down than the last.
Going it alone would be a bad choice but the Imperium can't and won't defend every single sector or system in its borders. Its one of the reasons why so many systems on the Eastern Fringe joined the T'au.

 JNAProductions wrote:

 Irbis wrote:
And keeping a handful of regiments is all cool and well, but Imperium acts like insurance - you put a little in, only to get a crusade in return when things went FUBAR and you really need it. What happens in RL with people who have no insurance but something bad happens? Oh yes, they go bankrupt...

That's the idea, sure. In practice... Well, how lucky is your sector?

Partially, I guess.

At its core, any systems standing forces are there first as a deterrent (PDF might not be up to much, but they’re still in theory plenty to put off opportunistic attacks), and there second as a stopgap.

The second bit is truly secondary. Intended to be well armed and numerous enough to hold out against larger threats until other forces can be brought to bear (bare? Never sure on that one)

This is just as important a factor to a successful planetary governorship as meeting your tithe. If either of those are judged wanting, you’re quite likely out. At the very least you end up with greater scrutiny. Given planetary governors are otherwise more or less left alone to get those two jobs done? Instances of the PDF being run down would be pretty rare. Not unheard of off course, but on the galactic scale pretty damn rare.

And again, it’s this layering of military forces which sustains The Imperium. Yes, it can take time for other forces to arrive in support. But that every planet, at least in theory, has some form of standing military, means your various foes also have to plan and wrangle up enough forces of their own to even think about it. Though this is what makes Eldar of all flavours a particular headache, as their approach is very much strike and fade, and they don’t need to rely on traditional approaches. The upside there is Eldar rarely (potentially if ever?) seek to oust another race from a planet.

Yes Eldar will defend Maiden and Exodite Worlds where it’s practicable, and whilst no examples spring to mind may seek to reclaim such a world. But for the most part, it’s in-and-out with specific objectives in mind. That could be slave taking, a quick bit of mass torture, just for the Lols (Dark Eldar), or to take out/protect a specific person or persons (Craftworld) or because this part of the rhyme and dance kind of requires it (Harlequins).

Orks? Outside of a full Waaaagh!, they’re also largely opportunistic. Raiding forces just looking for a fight wherever the Warp spits them out. The difficulty there is of things get protracted, more Orks might here about This Really Good Fight and turn up, escalating things beyond control.

The real threat to The Imperium are Xenos and Chaos Cults. Because they’re in plain sight, and can be difficult to properly notice, or judge the numbers of. I’d argue it’s a rare, possibly non-existent planetary system that doesn’t have some level of Cult activity. And they’re the sods most likely to throw a world into anarchy, even if they can’t always extend the strife beyond that planet (some can and do of course, but by no means all). Even if the uprising itself is put down by the PDF? There’s still going to have to be efforts to ensure it’s ripped out root and stem. And if you miss any Cells, or don’t come across other cults? You’re left with an inherently weakened PDF, even if the cult itself wasn’t able to infiltrate it. And if you don’t detect it, and send troops off to the Guard as part of your tithe? That’s bad news, isn’t it.

Hence Tau, Kyn and Eldar would struggle. They don’t tend to have a presence on most Imperial Worlds. Which means more traditional warfare with little to no chance to corrupt the defenders.

Now I still need to pick up the Votann Codex, so I don’t know how far spread they are in the background. But the Tau in particular remain largely in their (granted increasingly large) bubble. Eldar are few in number, and far flung. And not every world has handy Webway portal. Sheer, unrelenting attrition isn’t something Eldar or Tau can match The Imperium in, I’ll tell you that for now. Which means they can’t afford any military disasters. They just can’t soak the sort of casualties open war with The Imperium would inevitably lead to.

The Tau are probably the most vulnerable. Right now, they’re arguable too small a threat for The Imperium to spare much attention. But if they went on a proper war footing? Well, The Imperium knows where they live. And if it’s just Old Fashioned Retribution? Exterminatus could wreak absolute havoc, even if every Imperial asset in the retribution fleet is ultimately lost. Because again, The Imperium can soak those losses to a much greater degree.

Now a genuine gap in my knowledge is whether The Imperium has any way, regardless of reliability, of tracking Craftworlds. Yes they may be vast in scale, but they’re still a vulnerability which could be exploited.

But even those three together would struggle to tackle The Sol System or Terra, and that’s a big old spanner in the works. Unless you can cut the head from The Imperium? It’s never going to fall. Sure, it might be the work of generations to rebuild and rearm, but The Imperium would absolutely have the resources to do so.

And I think that’s ultimately why The Imperium has endured. Sure, it still lacks the numbers and breathing space to focus on blatting one particular aggressor, that’s true, but it’s foes either lack the resources or organisation to do heinous damage on their own.

Of course, Orks (specifically due to Ghaz), Necrons and Tyranids are something of an exception to one or other of those parameters. But even they have their flaws.

Yes Ghaz commands a staggering near inconceivable force of Orks. But even then, they’re Orks so command is a rather strong term. Berate, bully and point in roughly the right direction is about the best you can hope for, because The Boyz are always going to get carried away.

Necrons? Well, they could be anywhere (kind of almost making them a Cult type threat, in that you don’t necessarily know you’re in trouble until the uprising/awakening) and pre-Silent King has their own issues with truly uniting as a single force. Not to say it can’t or won’t be achieved, but the Phaerons are nothing if not egotistical.

Tyranids? A threat truly unlike any other. More numerous than Orks. More orchestrated on the field than any other foe. But….the Hive Fleets are slow moving. And they’re an equal threat to all the other forces abroad in The Galaxy, so it would never be a One vs One affair.

I believe the Imperium tends to have a rough idea of where a Craftworld might be mostly because missing a colossal spaceship with an equally large escort fleet is pretty difficult for monitoring stations (of which there are many) to manage. That being said, even if the Imperium knew where a Craftworld was, attacking one is an insurmountable task. The last time the Imperium tried to attack one, it lost an entire Battlefleet, a formation that ranges between 50-75 ships of various sizes. That's Tsushima levels of bad.

Thanks for the replies. I do think in a war of attrition the Imperium likely comes out on top. I would say it's a certainty but with the Fog of War there are rarely absolutes in war.

If they somehow coordinated a joint, decapitation strike on Terra and/or Mars it could be different. Civil War could break out in the Power Vacuum. Other factions such as Orks, Tyranids, Necrons, and Chaos could take advantage of the situation. The situation could deteriorate for the Imperium quite quickly, though vengeance would be severe. This has the advantage however of putting all the other factions in a defensive, possibly fortified/ambush position and with the loss of central leadership organizing a major Crusade could be difficult. The morale loss could be incredible as well.

Especially if they lose the Astronomicon. Can the Imperial Fleets travel through the Warp without the guiding light of the Emperor?

To me it seems a lot would depend on coordination and surprise vs Terra/Mars defenses as well as the Imperium's ability to maintain/recover political/ideological stability and unity after the fact. Primarchs could attempt to seize control, Planetary Governments could declare independence, the Ecclesiarchy could assert rule as well - challenging the Primarchs. Admech could fall into factional disputes or declare independence from the Imperium. Likely various factions could start blaming each other for the loss or at least looking for a scapegoat i.e. Sororitas blame the Imperial Guard who blame the Astartes, or even accuse each other of treachery and heresy.

As to how or why they would unite - Common Enemy. It can make for strange bedfellows - the USSR and United States in WW2; or England, Russia, Austria and Prussia during the Napoleonic Wars. I once read the two primary motivations for otherwise sovereign/rival powers to unite were 1 - Conquest and 2 - Forming an Alliance against a Common Enemy.

The Imperium seems heavily Centralized, Beauracratic, and Authoritarian. That can create a huge vulnerability. Often times it seems composed of various disparate powers held together by a thread.

Cut off the head and the snake may fall.

 Gert wrote:
I believe the Imperium tends to have a rough idea of where a Craftworld might be mostly because missing a colossal spaceship with an equally large escort fleet is pretty difficult for monitoring stations (of which there are many) to manage. That being said, even if the Imperium knew where a Craftworld was, attacking one is an insurmountable task. The last time the Imperium tried to attack one, it lost an entire Battlefleet, a formation that ranges between 50-75 ships of various sizes. That's Tsushima levels of bad.

On the other hand, the Invaders Space Marine chapter (deploying at chapter-strength) effectively destroyed Craftworld Idharae in 852.M41, so craftworlds can be pretty vulnerable.

I suspect they are kept hidden through various means, the most basic being that they travel in realspace, not the warp or webway, and therefore probably stay many lightyears away from inhabited worlds most of the time. I would be surprised if they were picked up by monitoring stations often- more likely by stellar observatories. The Eldar probably have some impressive stealth tech hiding them too.

The Iyanden supplement gave information that Idharae had been already weakened fighting against Tyranids as an ally of Iyanden, and the Invaders took advantage of this.

 Haighus wrote:

 Gert wrote:
I believe the Imperium tends to have a rough idea of where a Craftworld might be mostly because missing a colossal spaceship with an equally large escort fleet is pretty difficult for monitoring stations (of which there are many) to manage. That being said, even if the Imperium knew where a Craftworld was, attacking one is an insurmountable task. The last time the Imperium tried to attack one, it lost an entire Battlefleet, a formation that ranges between 50-75 ships of various sizes. That's Tsushima levels of bad.

On the other hand, the Invaders Space Marine chapter (deploying at chapter-strength) effectively destroyed Craftworld Idharae in 852.M41, so craftworlds can be pretty vulnerable.

I suspect they are kept hidden through various means, the most basic being that they travel in realspace, not the warp or webway, and therefore probably stay many lightyears away from inhabited worlds most of the time. I would be surprised if they were picked up by monitoring stations often- more likely by stellar observatories. The Eldar probably have some impressive stealth tech hiding them too.

A good reason for the Eldar to find allies against this existential threat. Even the Harlequins and Drukhari.

A good reason for the Aeldari to help Web-Way countless allied reinforcements to Sol. It's either they do so or face eventual extinction. And the Drukhari can take a lot of slaves on top.

Also if they entrench themselves on Terra and Mars, etc, the Imperium will focus their efforts to retaking these worlds - no matter the cost.

This could actually open fissures - as more rational leaders may note that with the Emperor and Omnissiah lost they have no good reason to keep pouring resources into the meat grinder when they can be going on the offense - whereas zealous, religious factions may wish to retake the Holy Worlds no matter what and declare all statements to the contrary " the highest form of Heresy since Horus." Better yet, in all this confusion various Planetary Royals/Nobles may try to take autonomous actions for wholly legitimate reasons, which factions like the Inquisition, Sisters of Battle and Ecclesiarchy may well interpret as acts of rebellious, heretical taint that must be dealt with by the harshest means, right away, without question, especially at this moment. And I'm sure Gulliman will just sit by to watch liberal use of Exterminatus. The Implosion will be glorious!

Gulliman: " You just wiped out a dozen key strategic, resource rich planets when we need them the most! Are you insane?!"

Battle Sister: " Why are you defending heretics? I knew you and the other Primarchs could not be trusted, after all Horus was an Astartes too Heretic!"

And all the King's Horses, and All the King's Men...

What else they gonna do? Let the million world, endless numbered, genocidal threat whittle away at them until there are no Aeldari left?

The Tau and Votann are not even close to being an existential threat. Whereas the Empire of Mankind is the greatest threat they ever faced since Slaanesh and in fact the Imperium have sabotaged Aeldar efforts to destroy Slaanesh.

All they have to do is ask 1 question - " Who wants to destroy the Imperium?"

 Haighus wrote:

On the other hand, the Invaders Space Marine chapter (deploying at chapter-strength) effectively destroyed Craftworld Idharae in 852.M41, so craftworlds can be pretty vulnerable.

Deployment of an entire Chapter to a single theatre is immensely rare though and you conveniently left out that the Invaders took massive casualties to the point where they were unable to defend their homeworld from a retaliatory attack from the forces of Alaitoc thirty years later.
So even with your example where the greatest warriors the Imperium has to offer deploy in full strength against a minor Craftworld has the Imperium taking huge losses.

 Gert wrote:

 Haighus wrote:

On the other hand, the Invaders Space Marine chapter (deploying at chapter-strength) effectively destroyed Craftworld Idharae in 852.M41, so craftworlds can be pretty vulnerable.

Deployment of an entire Chapter to a single theatre is immensely rare though and you conveniently left out that the Invaders took massive casualties to the point where they were unable to defend their homeworld from a retaliatory attack from the forces of Alaitoc thirty years later.
So even with your example where the greatest warriors the Imperium has to offer deploy in full strength against a minor Craftworld has the Imperium taking huge losses.

But at the same time the Imperium can replace marines (esp now with Primaris) far faster than the Eldar can replace all the lost infrastructure, life, technology, soulstones and more of that Craftworld.

Still the issue of numbers, forces and attrition.

The Tau may well number into the billions, sure. But only the Firecaste does the fighting. Well, and Air Caste pilots. Whilst I’ve no solid info on the split, that’s probably no more than a third of their overall population worth a damn in a fight.

Hence my comment that a single catastrophic defeat could entirely upend this theoretical alliance, because at least two of the races involved can’t match The Imperium in terms of sheer population and industrial base.

We also know Terra houses relics of the Dark Age of Technology. Weapons so awful they’re forbidden. But The Imperium being The Imperium? You know they’d turn them loose in extremis.

On Space Marine replacement in particular? The Primaris have somewhat sped things up.

If we look back to The Great Crusade, vast numbers of Astartes were created, killed, and replaced. And few if any Legions were working with prime stocks of would-be Marines.

That was possible of course due to the sheer power and knowledge of The Imperium during that period. And in later centuries, Geneseed degradation and overall scarcity as much as the Codex Astartes lead to exacting selection rituals. But how much of that is tradition and keeping to the Codex Astartes is open to debate.

We know Terra and other sites hold Geneseed Banks, tithed from Chapters for purity checks, the creation of New Foundings, and of course ensuring existing Chapters don’t have all those eggs in one basket should something awful happen, allowing it to be reconstituted over time.

But…with Cawl’s purer Geneseed (not purified as such, just…less manky) Astartes production could well be ramped up, allowing a swifter replenishment of Astartes.

And that’s just the Astartes. The Imperial Guard is near limitless in terms of replacing and creating Regiments. The current tithe is carefully balanced (as ever, in theory) so as not to significantly impact breeding stock left. But that can always be ramped up. Older model tanks and artillery can be brought out of mothball.

Piss off or threaten the Adeptus Mechanicus and you’re in for a world of hurt, as the can convert their entire stock of workers into fighters quite readily if needs be, nevermind the horrors they have lurking in their vaults.

I….just don’t see it working. To challenge The Imperium in such a way means turning your back on every other extant threat to your continued existence. So even if in a plot made from solid Narrativium succeeds? They may not have homes to return to, because no-one is about to sit on the sidelines and wait for you to replenish and rearm.

We also have the fact that right now? The Eldar….kind of need The Imperium. Not so much as an ally, but a useful stooge. Somewhere Waaghs, Hive Fleets and other nasties can be redirected to, that has a reasonable chance of extinguishing that particular threat. Not to mention The Imperium remains the best option for keeping all other threats in check, even if no-one is giving nudges toward certain outcomes. And for Dark Eldar? Humans are an excellent and unending source of slaves and victims. We breed like rabbits, and are mostly less truculent than Orks, certainly less individually dangerous than Tyranids. Do away with humanity, and whatcha gonna feed on in the numbers needed to sustain Commoragh?

 Overread wrote:
But at the same time the Imperium can replace marines (esp now with Primaris) far faster than the Eldar can replace all the lost infrastructure, life, technology, soulstones and more of that Craftworld.

Which doesn't account for the major Craftworlds and the other portions of this alliance. If the Imperium could track down all the Craftworlds and then destroy them, the casualties would be massive both in terms of troops and materials. In that timeframe, the T'au and the Leagues could press the advance or come to the aid of the Craftworlds. Plus, again that was one minor Craftworld.

I'm not saying this alliance would win, in fact, my first post said so. But denying that attacking Craftworlds is in any way not a major concern for the Imperium (because it is which is why it doesn't do it) is just silly.

 Gert wrote:

 Overread wrote:
But at the same time the Imperium can replace marines (esp now with Primaris) far faster than the Eldar can replace all the lost infrastructure, life, technology, soulstones and more of that Craftworld.

Which doesn't account for the major Craftworlds and the other portions of this alliance. If the Imperium could track down all the Craftworlds and then destroy them, the casualties would be massive both in terms of troops and materials. In that timeframe, the T'au and the Leagues could press the advance or come to the aid of the Craftworlds. Plus, again that was one minor Craftworld.

I'm not saying this alliance would win, in fact, my first post said so. But denying that attacking Craftworlds is in any way not a major concern for the Imperium (because it is which is why it doesn't do it) is just silly.

I'm not saying that its not a major undertaking, but rather that the Imperium can better afford the loss of life and resources in taking down Craftworlds than Eldar can take the loss of the Craftworlds. Even minor Craftworlds are major losses for the Eldar.

Craftworlds, of course, have great advantages. They are highly mobile and can use future predictions and advanced technology to avoid combat and make very precise surgical strikes. It actually means the Eldar might out-last the Tau and Votan in any alliance because the Votaan and Tau have established worlds, territories and fixed positions. The Imperium knows broadly where they are and can target and focus on them. Eldar would be that annoying player in an RTS Game who has 1 unit left who skirts them all around the battlefield hiding to deny you a victory because you can never find them.