Would it be a good idea for the imperium to just send a kill ship to Tsua'malor and wipe out the Tau centre of gravity once and for all? That would probably cause the Tau war effort to collapse, and allow the Imperium to destroy them, then focus their efforts on the other two fronts. How sound would this strategy be?

peterstepon said:

It writes off an inhabitable planet. Those are rare things, and the Imperium doesn't wipe out planets unless it *really* needs to.

Warpships needs to exit the warp far from a gravity well. This means that system defence fleets have three or more days to organise a defensive line.

Capital Worlds are likely to be defended by huge fleets. Ships build for planetary defense don't need to be warp-capable - this means they can pack more punch for their weight. Essentially any such attack would meet an overwhelming defence.

Having said this, the real reason is that it wouldn't make a good story. A planet killing nuclear warhead isn't very difficult - meaning that it is feasible by 20th century engineering (let alone 21st or 410th)... You could fire thousands of missiles. You don't even need to get to the surface. Exploding a device with enough yield in space would kill 50% of all life on a planet.

And just have a "freak" warp storm stop this one from going off too? Nah Tau live a charmed life vs exterminatus its better to just go down and chop them limb from limb.

I think you have to assume that Exterminatus isn't a viable strategy against a target that can actually defend itself. The Imperium certainly has the firepower to flatten planets, but that's not the same as being able to get into a *position* to flatten those planets.

Exterminatus connat be done in a single stage warhead. It needs a multistage borbardment.

1st the virus bombs turns everything biological to volatile gas then they use high yield explosive to ignite the planets asmosphere and create a gigantic slow coocker. takes a while to do.

Fresnel said:

Well, it's not a necessity so much as a really good idea - the suggestion I've seen is that emerging into or departing from a strong gravity well places extreme and rapidly-changing stresses upon a starship translating to or from the Warp (one moment there's no gravity, the next there is, or vice versa). For most people, that's good enough reason to translate a safe distance away from a star or planet.

Most people... the Ork invasion of Rynn's World managed to bypass a lengthy orbital conflict due to emerging from the Warp extremely close to Rynn's World itself, destroying much of the Ork fleet (but not enough that it made any difference) but leaving the defensive fleet with no time to organise a proper defence.

N0-1_H3r3 said:

I can Imagine there's a fair amount of shock going through a ship just going from the insanity of warp space to a real space without suddenly finding yourself tumbling in a gravity well, so I can totally believe that.

Also doesn't warp travel get less accurate the further you jump? Obviously navigators can cover huge distances but if you can't arrive at the time and place as the rest of the fleet it's going to easy pickings for defenders.

crisaron said:

You know I've heard multiple takes on this, I think it depends on the style of exterminatus. Cyclonic Torpedos are discussed as being able to burn the air or melt the planet's core death star style. I've not seen or read much to back up a planet killer one shot, but I am pretty certain Medusa IV was razed by lighting it's atmosphere on fire with a salvo of atmospheric incinerators.

At the OP, I think Fresnel's comment sums it up well in that it wouldn't make that compelling of a story. The other posts I think do a pretty decent job of describing why one wouldn't want to in Imperial thinking; it would be exceedingly difficult to get into position when attacking a fortified position and you're looking at making a world inhabitable for an extended period. Soldiers are more replaceable than planets.

Also, when you read the descriptions or look at what people say about Exterminatus, it's a last resort, much like our "Nuclear Option." You only use it when the threat is too great and can't be contained by other methods. The crusade may be at a tipping point but the war is by no means lost.

Deathwatch Kill Ships are cloaked and capable of devastating an entire planet by themselves. They sneak in, drop their load and fly off as the planet explodes. Yes, they simply are that "good" (did I mention they don't need a Navigator either?).

Why not use them? Plot hole. Or story reasons, as Fresnel mentioned, if you want to make it sound more amicable.

N0-1_H3r3 said:

I've just finished this book actually .

In any case, it would be a matter creating a stable warp-exit/entrance, rather than the gravity gradient itself - which would be tiny. No imperial commander would risk a 50+% loss of his fleet on an attack. However, he might use it an escape tactic if he faced certain loss otherwise - as the last Crimson Fist Captial ship did.

In the real world, nukes have been proposed as defence against large meteor collisons. Apparently a nuke capable of knocking a planet-killing meteor off-course is well within practical engineering limits. It's mere existance probably presents more danger to life on Earth than meteors though...

Sterilising a world isn't very difficult. Life is very fragile in the grand scale of things. You don't need to explode a planet Deathstar style. A single nuclear device, no bigger than a car will do the job. Or find a big meteor and push it into the correct orbit- shatter it and you have 10,000 objects capable of killing a world. The WH40k is grim, but in the end it's heroic fantasy.

Fresnel said:

Nukes aren't that powerful. ?

Current designs of nuclear warheads range from tactical to city-killer. They are designed to fill a military role - doomsday is not a military objective. No nuclear power has thus far wished to own a doomsday weapon. The limits are practical, financial and political. Fortunately the first two put such a weapon beyond the budgets of Isreal, Pakistan and Indian. Plus not even these are mad enough to want one (I hope).

Luckily, North Korea can't seem to get a simple fission device right. However, were they to develop the knowledge base and expertise needed to create a viable fusion (hydrogen) bomb there is no theoretical limit to the potential yield of devices of this type. Fortunately they are far away from building such a thing.

That said, this is the 41st millennium. If the Soviets were capable of building a nuke that can burn stuff in a radius of 100km (and that was the "lite" 50 megaton test version - the true beast was designed for 100 megatons) I'd not rule out the possibility that the Imperium of Man has an atomic device capable of punching a big hole through a planet's crust and/or introduce it to centuries of nuclear winter. Of course it likely also depends on where exactly you drop it, and the qualities of the planet in question.

I'm not entirely sure what Kill Ships are carrying, though - their blurb in the Core Rulebook just says that, whatever it is, it's enough to cause planetary apocalypse, though this term may be a bit ambiguous in terms of determining the actual effects (there's a difference between killing everything on the planet and "just" forcing everyone to don a protective suit, after all).

"Why not just send a kill-ship to Tsua'malor?"

answer is very easy, as everything that have something to do with anime blue comie bastards with hoves its called "Plot Armour". Only reason why they exist.

Fresnel said:

Yes, but these aren't particularly gargantuan, the theory behind this is that you'd create the explosion near the object several years before impact, which would only change the meteor's course by a couple of centemeters, but when dealing with range and trajectory 2cm is all that you may need. Some of the models are done with nuclear devices under a kiloton in yield.

Fresnel said:

True, and the meteor theory is a clever one, though why not just shove the meteor into the planet? Though I'd argue a car sized nuclear device won't do the job, as the current theoretical maximum yeild of a nuclear warhead is 6 megatones per ton of bomb. The big one the Russians tested was a 50-60 megaton yield and it was something like 25 or 26 feet long and 27 tons. Now of course this is in no way 40k physics...

I still think they key point, regardless of exterminatus capabilities or delivery systems it that it is a last resort- maybe it's a last resort due to plot armor, but you don't just go around blowing up planets because you want to win 1/3rd of a crusade. You use the exterminatus when there was no hope of reclaiming the world now or later, or if whatever threat existed on that world was is greater than the value of the whole planet (like an enslaver plauge or the creation of another anomoly). I wouldn't consider the Tau command center a threat of that magnitude, expecially given the wierd cooperation the Empire has from time to time with the Tau.

The Soviet one was designed for 100 megatons, they just purposely lowered the yield shortly before the test, but that just as a sidenote. All of that doesn't really apply to 40k anyways, as you said. Apart from it being a fictional setting with its own laws of physics, they could easily claim technology had advanced far enough to allow pocket-sized nukes having the same effect as the Hiroshima bomb, and larger ones being capable of blasting a planet into bits - just compare Little Boy's dimensions to that of a B41 device. About the same size, but where one sported a yield of "only" ~15 kilotons, the other had a whopping 25 mega tons. Progress, if we want to be cynical.

Charmander said:

Because Rocks Are Not Free , citizen!

By the way, we do have an official example for how an Exterminatus could look like - one of the possible endings for Final Liberation included a cutscene that has the Imperials trigger one as their cruiser withdraws, due to the planet being overrun by Orks and the defeat of the troops on the ground: http://www.youtube.com/watch?v=CJTp3vxxOY0

Lynata said:

HAHAHA, nice

Lynata said:

Hahaha! I never thought that game would be used as a point of reference here. The good old days when they all though live actors were the future!

SPOILERS:

DoW II: Retribution Spoilers:

Lynata said:

If we're looking at the same sources (the short sidebar on p 310) all it says is that they are equipped with "the most valuable of cloaking devices" and that "their mission is" to sneak into a system "past whatever sentinels the invaders may have put in place at its edges".

This does not read, to me, as stating that Kill-Ships are infallible, unlimited range planet killers, rather that they are a last ditch effort to enact Exterminatus on a planet which is *presently being attacked by Aliens*. (Their targets are specifically described as "worlds lost to the Imperium").

I don't think it's that much of a stretch to assume that while the Kill-Ships are good enough to sneak past an alien invasion fleet and blow up an *imperial* planet (if nothing else, most aliens wouldn't expect that the Imperium would *do* that) they're not good enough to sneak past the technologically advanced defenses of an alien homeworld.

Charmander said:

Yes, I concede that it would be a heavy device - but the imperium is hardly shy of large scale engineering. The question is, what kind of attack would a Exterminatus require? Does it need to ensure a total destruction down to the deepest bunker?

A single 10 gigaton device might be an exiction level event. An industrial society might not survive it. But to competely fluidise the Earth's crust would require a larger device. The visualisation from DoW:R show a single device... Perhaps an anti-matter bomb?

I think the meteor plan would be more feasible (an old Science Fiction concept btw).

Chastity said:

Meh, maybe you're right, but I still think Kill Ships were simply made way over the top, reducing what until now usually required an entire flotilla of Imperial capital ships to a single unmanned vessel, which also doesn't need a Navigator to steer through the warp, and of course it's available only the Deathwatch. I've got no clue why they even came up with this idea. It sounded cool, I guess.

Speaking of the Tau, here's another Exterminatus:

Fresnel said:

Charmander: Phht, I still think the actor of Holt would have deserved an Oscar nomination for his performance.

Fresnel said:

If you're going to the trouble of exterminatus you want everything dead, not just the people on the surface. Even if society crumbles, military structures and chaos infiltrators and enslavers can still live and cause problems.

http://wh40k.lexicanum.com/wiki/Exterminatus

Charmander said:

I don't know. the virus bombing of istvaan left structures standing and even hundreds or thousands of astartes alive because they were deep enough underground. admitedly this wasn't really an exterminatus but a similar level of damage.

to be honest I think to neutralise the tau you would have to fragment the planet. even if you detonated a 1GT device and caused a complete nuclear winter I think tau civilization would be advanced enough to survive.

on another note I agree that my impression of kill ships is not that they are designed to slip past planetary defence nets but rather that they can sneak past invading fleets to destroy defenceless planets that will be overrun otherwise. it only takes a dozen or fewer cruiser and battleship class ships to invade a planet, but the tau homeworld likely has hundreds or thousands of overlapping sensor nets to slip though

Lynata said:

Not really.

Sending a small ship with a heavy payload to blow up an enemy planet is something you'd expect. Sending a small ship with a heavy payload to blow up a *friendly* planet isn't something most enemies would expect.

Kill-Ships are only described in a small sidebar on one page in the core rulebook, the way I see it you can either assume that they're supposed to be more powerful than anything else in the universe, but somehow never to be used for all the things for which you would use such a powerful weapon, or you can assume that they aren't. There's nothing in the small sidebar which introduces the concept which declares them to have unlimited destructive power, or to be infallible, or to be any use whatsoever in attacking a hostile world.

Charmander said:

I suspect that part of the problem here is that "Exterminatus" probably has more than one meaning.

If the problem is a corrupt society, you just have to annihilate that society. If the problem is corrupt thought, you just have to annihilate the majority of higher life-forms, it's only if you want to wipe out - say - an infestation of Tyranids which has infiltrated the ecosystem down to the cellular level - that you need to wipe everything out to the nearest microbe, and only in the event of serious Daemonic infestation that you need to eradicate the entire planet.