So, sometimes I ask dumb, pointless questions; it's a weakness of mine, and this is probably going to fall into that category. What are the actual defenses of Earth itself probably like? If I wanted to deal a crippling blow to the Imperium, Terra would be an ideal target. This is irrelevant, I confess, as nothing in the RPGs could go further from where they happen than back to Terra, but if a plot was discovered, it could be an interesting twist. The Emperor rests there, but some of its protection might be "who'd be so nuts?", meaning some is a bit of a bluff. Now, if I was some roving Chaos Warband, with a big fleet of nasty, I wouldn't hold out much hope for my chances, but what if I was one mad person, either a psyker tainted by the Hive Mind, a servant of Choas willing to use "exotic" methods, or even a ship-established Genestealer Cult? What's to stop one small ship from landing on Earth, out in one of the arid slums, and let loose one or more Genestealers I might be carrying? There has to be limitless traffic above the ruined planet that was once the cradle of Mankind, with numerous warships of the Battlefleet Solar, Black Ships dropping off their psyker-quota, various Adepta craft ferrying envoys to or away, and pilgrimage ships bringing the faithful, or their descendants, to bask in the glory of the birth planet of the Immortal God-Emperor of Mankind. My ship would hardly draw the notice of the Battlefleet, and Earth probably doesn't have too many Space Marines. One little ship wouldn't seem to hard to land, or force-crash, and let loose a plague that could spell the doom of the Imperium. One Genestealer laying low + 30 years of peace among the crime-ridden slums of Earth (for being the capitol of the Imperium, Terra is no garden spot to live) could equal a very hard to get rid of Genestealer Cult, and while it might not topple Earth, as it would many colonies, it could draw a Hive Fleet. Such a force might even, through it's Shadow in the Warp, blot out the Astrnomicon at it's source, crippling much of the Imperium for as long as it takes to dislodge the Tyranid menace. I'm not saying Earth would fall, but it MIGHT, and it would be a big hit to the Imperium everywhere else, from logistics to morale.

One might say "yeah, well if it was that easy, someone would've already done it, you dimwit. They've been writing this stuff for several decades now", and that would be true, but I don't see the hard part for the aggressor, if their threat is so small, and seemingly trivial. Thoughts?

The entire Sol system is made and concieved to protect mars and the Emperor.

Billions of fanatical pilgrim are on earth ready to sacrifice themself for the Emperor.

There is a navy fleet there at all times, countless defences, nothign goes in and out without being searched and boarded countless times.

The Grey Knigths are based in the system, the DeathWatch probably have their own base and the sister have the moon if I remember well…

Chances are slim… and besides there are probabl nastier things then even genestealer in the lower levels of earth… countless murder servitor roaming the catacoombs.

Then you have the custodians "marines"… so no I doubt…

Earth is well protect, you will find there:

- A sector fleet based on solar system

-Several Astartes chapter in guard

-the grey Knight

-All the officio assinarium order and their assassins

-Several million of fanatic from pilgrim to ecclessiarchy "guard"

-At least two titanic legion and all the skitari Mars can afford

-PDF and SDF in great number

-Lot's of Imperial guard regiment for countless numbers

-Adeptus sororitas have indeed if my memory work fine a fortress in system

-Syster of silence

-Numerous and onerous Inquisitorial asssets from cells to army

-Adeptus custodian

-All the psyker you wish to put there because their "school" is there

-And a lot of enforcers

-mainly all the private army of the high lords of terrra

If Horus and 9 legion haven't made it it is not a single menace that will bring earth down.

If it was possible abaddon would not try once every 800 years to launch a black crusade.

Remember last time people came here to blow earth there was primarchs with them and it was not enough.

Besides the conjecture above we can be sure of the following. (Based from Battlefleet Gothic 2002 Annual, an account of 3 Necron shroud ships making an ultimately suicidal run on Mars in 992M41, known as the Mars Gambit.)

A deep space, early warning, monitoring station on Titan.

A large number of monitor defence flotilla's. Monitors are small, slow defence-oriented ships loaded with a large number of weapons, they are only effective when defending a location. (Several flotillas were able to be deployed against the Mars Gambit and this considering the Imperials didn't notice the stealth ships until they were practically at Mars' doorstep. Meaning the flotillas were close enough to intercept even with little warning, indicating there are massive numbers of them throughout the system.)

Multiple large orbital minefields around Mars (Earth likely to have the same). Enough to disrupt tracking on the Shrouds, though shrouds are stealthy by their own right so that helped in the situation. The Shrouds didn't set off any mines, due to their stealth systems.

Deimos and Phobos lines of orbital weapons platforms with numerous weapons and overlapping fields of fire. The rediculous speeds of the Shrouds carried them past Deimos before they could respond after leaving the minefield. Phobos line heavily damaged a Shroud, which was then destroyed by one of the others, the explosion overloaded augeries, allowing the other two stealth ships to break past.

An orbital protection fleet (of unspecified number) for Mars itself. Launching over 120 starhawks on multiple missions to engage the Shrouds as they attacked mines in Noctis Labyrinthus, destroying both ships, although one ship managed to land before being destroyed.

This is just space based around Mars, imagine Terra would have even more significant defenses.

As stated Shrouds have very strong stealth abilities, and are terribly fast, faster than other necron ships which all use inertialess drives and are themselves fast. No imperial ship capable of catching a Shroud could beat it one on one. This ship is perhaps the most capable of penetrating Sol defences, and it did so more with suprise and speed than with power. Had those ships been detected earlier the outcome probably would have been different.

That was pre Ward fluff too… When the Necron where cool anyways and working for the C'Tan.

Now they are lame. I doubt that the all the fluff about a big part of the mars priest secrelty workshipping the Dragon (a C'Tan) still stands.

Got to hate Matt Ward

Mat, not Matt

crisaron said:

I could tell that because it implied both Phobos and Deimos were orbiting Mars. WARRRDDD!!!

Personally I think that taking Earth is theoretically possible but it such massive endeavour that it practically impossible. Such a large fleet is going to be required that you are going to need to launch it from a nearby system just ensure enough forces arrive at once to muscle through.

Unless you have some massive technological or psychic advantage which, of course, the Imperium specifically tries to counter.

In case of some freak large scale deamon manifestation they have the Grey Knight fortess monestary and the 'home' of the Ordo Malleus. For psychic threats the home of the Adeptus Astra Telepathica (and I suspect where they are hiding the Sisters of Silence).

http://wh40k.lexicanum.com/wiki/Sol_System#.ULYV1uQvRSo

What Herichimo describes is probably fairly standard defences around all of the of the populated planets and moons and the monitoring station on Titan also probably has similar large monitoring facilities on all major moons and planets, the titan one jsut being pertenant to the story.

Ground force wise Sol doesn't just have a large number of Imperial Guard regiments but also the remaining genetically augmented Guard regiements that pre-date the great crusade.

The Imperial Fist have a Chapter Keep on Terra but it's noted that they bearly maintain a presence there (pressumably it was decided that such a famous chapter was better off 'flag waving around the Galaxy') but it wouldn't surprise me if there were 1 or more successor chapters raised specifically to defend the Sol system exclusively.

Everything the above posters have said. To summarise again incase I hit something anyone missed:

Terra is guarded by Battlefleet Sol, which is the largest battlefleet in existence.

Luna is basically one giant battle station (That's no moon…)

The Adeptus Custodes, two titan legions, the sisters of silence, and the Terran guard are all active on Sol

Its the Imperial Fists homeworld…

Something else to keep in mind is that there isnt actually much space on Sol that is 'slums'. Its a hive World by nature, but compared to the rest of the Imperium its pretty much a paradise world if you live there. The entire northern hempisphere makes up the imperial palace too, so the availible space for non guard forces is slim.

If you wanted an attack on Terra it would have more chance of success if it was a political based machination rather than an assault. A rogue agent influencing a High Lord, or a schism based on breaks in dogma between the Martian Fath and the Imperial Creed would be much more likely to bring the planet to its Knees.

However, something that is important to remember with this type of idea is the in reality the Imperium does not operate on a single government. Due to problems with communicating over the span of an entire galaxy most subsectors go up to centuries without world from segmentum Sol, and are as such operating independantly for most of their existence. The Emperor and the Astronomicon (which are really one and the same) are the only real strategic assest on Sol that would have a lasting loss on Imperial Forces.

See, that's why I suggested something "small". I'm not sure how hard it actually is to land on Earth, if you can trump up or possess a legitimate reason, or if you approached, and then hard-forced a crash landing. Most of the things listed above would be terrifying, if I was a Warmaster of Chaos, or a Master of the Necron Fleet, and was leading a force to assault the planet. But if you could fly past all that, and actually land planetside, many of the other defenses would seem not to great. I don't remember Space Marines being on Terra, and the people are terrified of them; I would think that, rather than risking another Legion trying to claim the planet, other forces (IG, SoB, SoS, Ecclesiarchy) would be defense, while the limited numbers of Space Marines would be abroad in the galaxy, fighting wars. Genestealer Cults are notoriously hard to find, though, and make efforts to not be detected. A lot of the defenses of Earth wouldn't be actively looking for them, and there are billions of serfs, with nothing to keep them safe. Over some time, they could infect a number of people, and while they might not topple any institutions, or maybe even bring in said Hive Fleet (I imagine the Hive Mind has an idea of how foolhardy trying to take Earth might be), some damage, and a lot of suspicion and negative morale could result.

venkelos said:

I see what you are saying; most of the replies are responding to title of the thread (How hard is it to assault Holy Terra? Ask Abaddon- there's a reason why it's taken him 10,000 years to build up the rescources to have a legitimate shot at it…), and not your original post.

That said, I have to assume that security on Terra is just as tight at a persomal level as it is on the macro level. If you really want to deal a crippling blow to the Imperium without grappling with issues of Terra's literally monumental defenses, might I recommend targeting Black Ships en route to Terra, rather than Terra itself? The fluff makes it clear that it takes 1,000 psyker sacrifices a day to maintain the Astronomicon at its current levels; even a slight reduction in collection of psykers could cause a signifigant contraction of its signal, leaving many systems high and dry… Mind you, this is no easy task- Black Ships are specially warded against the warp/ psychic powers, and they have the entire might of the Imperial Navy as back-up. Still, it would be easier than attacking the heart of the Imperium directly…

Adeptus-B said:

Fortunately for Cadia, this is not the case. He hasn't been sitting building up for 10k years. There have been 13 Black Crusades, major chaos incursions from the Eye of Terror in thes 10,000 years. many of them led by Abbadon himself.

Lets also not forget time dilation in the warp. It could have just been 3 weeks for Abbadon! ;-)

Also, while this is kind of off topic, it's important to remember most of the Chaos legions are now at a massively reduced strength of numbers and most have fractured into smaller warbands. Chaos is, well, chaotic and doesn't operate as a unified force against the Imperium. Even is Abaddon were to throw his entire (much reduced) legion in whole, it's doubtful he'd break Cadia's defences let alone Terra's

Cail said:

Actually in the last crusade Cadian was taken by chaos! ;)

So? That doesn't disprove my point. A black crusade is when the forces of chaos do unify for a massed assault, thats what makes them scary. I was referring to a unified assault by the black legion. A crusade is the exception, not the rule

Crisaron:  erm, from what i understand, only one continent of Cadia was taken by Chaos in the last Black Crusade, and the Imperium still rules space.  Just sayin' :)

As already mentioned there is no possible way to attack terra with a large scale force and be sucessfull.

But even if you consider "small" forces you have to think about lots of security mechanisms. First of all the Inquisition keeps an eye on Terra, they are the watchdogs and if you talk about the importance about the high senate possibilities are quite high that no senator enters the senate without all tests the imperium can make to be sure they are not mind controlled, possessed or something else. The same accounts for their households. Just think about the power of their personal security troops that are in fact real armys. Even a navigator house has its personal guard made of space wolfes! A senator might then be even guarded by individuals that could be compared to temple assassins. To compromising the senate by force is a hard idea. Though forcing some shisms might be more sucessfull.

And infiltrating the imperial palace… forget it. The adeptus custodes guards the palace and they have their own "blood games" where custodians try to infiltrate the palace against their brothers. And nobody cam even near the golden throne. But just think of the custodes… they are the last true Legion, 10.000 Man at arms… not juste mere man… even not space marines. They are something greater. Imagine the fusion of an temple assassin and a space marine. An example: The former chief-custodian Constantin Valdor defeated Horus, a primarch, in a sparring fight before he was gifted by chaos. As far a space marine is superior to a man, a custodes is superior to them. And their gear is ancient "state-of-the-art". Everything they field into battle would be considered by other chapters as a venerable relic, nearly to important to allow it to be fielded. And it is not even unlikley that a lot of the custodes are in fact veterans of the great crusades or even the unification of earth, at least in their ancient design dreadnoughts.

The custodes had been made "OP" because there had to be something to make terra immune to the countless enemies of the imperium. All the other forces guarding terra have been seen defeated in other conflicts, but not the custodes. 100 Space Marines can win a full-scale war. 10.000 Custodes make Terra a fortress nobody can hope to take.