Here, we get to some more stuff relating to the tactical/strategic situation between Imperium and Tyranids. I like this mainly because of how it relates to us the Imperium's warfighting capability, and (to an extent) puts all other threats (and the whole "Galaxy at War" atittude) in real perspective.
Also, if you didn't get enough of me mentionin Tyranids surviving Exterimnauts or jus thow hard they would be to nuke-spam, here's yet more conclusive proof. Also, more on the "biomass denial" trick Kryptmann was ostracized for. Poor Kryptman.
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To summarise, our strategy in this regard has been the doctrine of 'Biomass Denial'. A Tyranid hive fleet must expend a staggering amount of energy in taking one of our worlds provided our forces are able to mount an effective defence. Frequently, we have been able to draw the hive fleet into committing ever increasing reserves of energy into taking the world, at which point, we attempt to withdraw the bulk of our forces, ,and deny the hive fleet its price, by way of enacting Exterminatus upon the target world. This has the effect of critically draining the hive fleet's resourcecs, as it has no biomass with which to replenish the energy expended in taking the world."
Here we see the Anti-Tyranid tactic defined as "Biomass denial" One assumes that by energy they mean "effort", since a Hive fleet usually recovers mass from most planets, not energy. (we dont knwo where they get energy, but its presumably from the warp like most biowank.) Though this may imply some sort of "matter/energy" conversion as well.
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It is becoming apparent that such a strategy will in the long run prove too costly, for the Imperium does not have an endless number of worlds that can be sacrificed in such a manner. With our worlds spread so thinly across the void, each one lost is irreeplacable.
Note that in the codex, the timeframes between hive fleet attacks has varied between 2 millenia (Colossus), to 1 millenia (Tiamet to Ouroborus), to 250 years (Behemoth to Kraken) to only a few years (Kraken to Leviathan, ~4 years)
I'm not too sure in what context one might deem this tactic infeasbile in the long run at least at the current way the Tyranids attack. The Imperium is always adding new worlds - dozens if not hundreds, as well as losing worlds to other things. Losing/gaining worlds is a fact of life for the Imperium, and even on the scale of destruction this Hive Fleet required, its not a major loss (The Imperium has suffered worse.) Especially since you can expect years at LEAST (if not decades) between hive fleet attacks (unless they continue to get faster or more numerous.)
Another way to look at it is to consider Guard regiments and colonisation. "Successful" regiments are commonly utilized in conquering and colonizing new planets. With at least "millions" (if not billions") of regiments, even a small fraction should yield many thousands of Guard regiments that parrticipate in such efforts every generation (if not less) That means scores of worlds added each year (again, minimum) not incluiding other explorator fleets, Space Marine and Rogue tRader conquest/colonisation, rediscovere/reclaimed planets already inhabited by h umans, etc. In a fashion, they CAN afford it, although they may have to be selective in the kind of world they lose (Some places may have more than just a habitable planet to lose - precious resourcecs, technology, etc.) While others are so old/established their loss might be more tangibly felt (A Forge World or really old Hive World like Necromunda or Armageddon, for example)
Loss of precious resourcecs/technology, however iwll hav eno influence on the vaibility of the tactic with regard to timeframe - losing them now or losing them in the long run, they're still lost.
This all also only remains true so long as the Tyranid pattern of attacks remain fairly constant. IF they decide to launch dozens of Hive Fleets on simultaneous attacks, for example, "biomass denial" would become far less effective.
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Reports have reached the Strategic Collective of a number of instances in which Tyranid bio-forms have, against all previous precedent, survived the Exterminatus of a world targeted by them.
Well, so much for biomass denial. Note that some of those methods (IE cyclonic bombardment) can correlate to a nuclear attack, so we yet again see that nuclear attacks against Tyranids are not nearly as effective as some assume (At least, against hte larget forms.)
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There are two reported methods by which Tyranid creatures have survived the destruction of a world. The first, which has been confirmed at Tethris and Caelus Delta and is suspected at Lamarno, is achieved by way of smaller bio-forms, such as Rippers, burrowing deep beneath a world's crust, there to enter a state of hibernation until such time as the presence of life upon the surface is detected.
....
The second observed manner in which Tyranid organisms have survived Exterminatus was reported to the Strategic Collecive following a Deathwatch mission to the world of Ariadne V. Following exterminatus by way of Damnatus-pattern, mass-yield cyclonic saturation, the surface of the world was reduced to drifting ash, the amotsphere entirely seared away. Yet pict-logs of the mission show what was at first believed to be a natural rock formation rising out of the s wirling dust storms. Closer inspection revealed the truth - the structure was in fact a member of the Carnifex genus, which had survived the cataclysmic effects of the cyclonic torpedo, and entered a state of dormancy within which it could mend the grievous wounds done to it. The moment the creature detected their presence and began to stir, the Killteam called down a melta torpedo strike from their cruiser in orbit. Though the beast was destroyed, Ariadne V is declared Perdita, for, if one such bio-form can survive, then how many more may go undetected.
These examples have interesting implications.The first suggests that some forms of Exterminatus are only a "surface" extermination. That is they can be expected to eliminate all forms of life on the surface of a planet, at least up to a certain depth. But that such bombardments do not, as a rule reach deep into the crust, and so may be avoided by certain cases. (logically, this suggests hundreds of meter,s, since we know the Imperium can bury bunkers and defenses, ,esp planetary defenses, this deep for protective reasons.) From this we may conjecutre there are other kinds of "deeper" penetrating Exterminatus, such as conventional (lance, battery, torpeod) bombardment which will. (It also suggests that you can expect sucah bombardment to melt/pulverize the crust up to at least a kilometer or so in depth, possibly more, ,be it Tyranid infestation or not. Which in turn suggests the energy requirements for exterminatus extend well into the e26-27 joule range)
THe second example is frmo a cyclonic bombardment, with the result of superheating the atmosphere (and cremating all life on the surface) as well as blowing said atmosphere off (E25-2e26 joule range) delivered by a single (or small volley) of torpedoe(s) from a single strike cruiser. And yet, a Carnifex survived, whcih establishes (Broadly) what kinds of forms we coudl expect to survive severe temperatures for an undefined period of time (which in turn tells us how resistant the Tyranids are to forms of attack such as nuclear. As if I need to further emphasize this point.) Carnifexes are larrge forms, but certainly not the largest the Tyranids have lying around./
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These instances make it clear to the Collective that no consideration should be given to re-colonisation of any world touched by the taint of the hive fleets for, even should the ultimate sanction of Exterminatus be enacted, there is sufficient cause to doubt its total effectiveness. All such worlds are to be declared Perdita, on pain of death, to any other than those authorised by this collective to step foot upon them.
In other words, any world potentially touched by the Tyranids is probably in the same boat as the ORks - you'd enver get rid of them. So the issue of whether or not biomass denial is a viable long term strategy is further irrelevant, basically. (Poor Kryptman.)
It is interesting that this implies that at least some worlds put under exterminatus
can be recolonized, at least in some fashion.
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It is the belief of Strategic Intelligence Collective 827/II that current mobilisation levels will need to be increased a minimum of 500% if we are to even stand a chance of slowing the advancec of the Hive Mind. Every able-bodied man and woman on every world in Ultima Segmentum, Segmentum Pacificus, and Segmentum Solar will need to be drafted into the Imperial Guard if we are to have any chance of repelling this foe.
This is an interesting quote as it pertains to the level of militarization of the Imperium. In a galaxy of WAR, when it is stated tha thte Imperium is under constant threat of annihilation, it is felt feasible (at least by this group) that the Imperium could mobilize even more troops without significant apparent disruption (At least five times more, possibly more) in 3 of its five segmentum. This does bear out with the level fo troops typically requisitioned vs PDF and planetary populations. One also presumes similar level of mobilization amongst the Navy and such (Since fighting the Tyranids is as important in space as on teh ground.)
Another way to put it is: the threats to the Imperium, while they exist and while they could do damage if they go unchecked, are probably exaggerated (for propoganda purposes - war is a teriffic unifying element.) Otheriwse, one would think, the Imperium would have already mobilized.
). Given as you rightly point out the near impossibility of doing such a thing, it is far more likely that the Collective is pointing out that new methods for fighting the Tyranids are desperately needed. I know if I were a High Lord and reading that report I'd start looking into alternative methods - I'm sure a massive expansion in the Imperial Navy would be more efficient for example.
