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People underestimate what can and cannot be done. A strike cruiser in orbit would take years to reduce reistance to a Space Marine strike on Earth. Even a full Chapter would be overwhelmed if dropped unsupported. That being said, Space Marines do not invade planets with just a Strike Cruiser. They are backed up by millions of Imperial Guard troops and fleets of battle cruisers. Depending on preliminary orbital bombardment and warning times for Earth, the Marines would be very effective at creating a beach head for those millions of Guard troops to land and percecute a ground war against Earth. It would be a very bloody ground war, but eventually Earth would fall. I would give most areas of Earth no more than one year of effective resistance in case of a full scale invasion. A single chapter would be useless though.

Why do we know they're coming? Why are they unable to scout and infiltrate vital objectives (teleport homer in an air duct would do wonder)?

You really can't use table top marines as the standard. Even their own codex's paint a much more lethal picture, not to mention Imperial Armour and such. GW has consistantly said that SM are toned down to make the game playable.

If we get nukes and everything we have, why don't they get viral bombs, and entire chapter fleet, cyclonic torps etc?

I'm not sure how we stand a chance.

 Lobukia wrote:
Why do we know they're coming?

Because we have active surveillance of local space around earth?

Why are they unable to scout and infiltrate vital objectives (teleport homer in an air duct would do wonder)?

I've never heard of such precision teleport capabilities in 40k, and how would they know where the air duct is and that it's a vital location in the first place, and would a genetically engineered 8ft tall 500lb supersoldier fit?

You really can't use table top marines as the standard. Even their own codex's paint a much more lethal picture, not to mention Imperial Armour and such. GW has consistantly said that SM are toned down to make the game playable.

Using Imperial Armor as the standard, the entirety of the Astartes would have been wiped out on Vraks had they tried to undertake that operation.

If we get nukes and everything we have, why don't they get viral bombs, and entire chapter fleet, cyclonic torps etc?

Nobody is going to dispute that if SM's have viral bombs and cyclonic torps, it's over, but at that point it's a matter of pressing a button in orbit and destroying the planet, not conquering it. Fleets can be destroyed in orbit, 40k fluff makes it clear nukes are still very potent weapons and we have thousands of them able to be delivered into space, and the second it comes to war on the ground or the atmosphere, it's over for the Astartes. They die like anyone else to heavy artillery fire, not just on the table but in fluff as well, and we have tanks that can move, shoot, and hit targets with near 100% accuracy at distances measured in kilometers at highway speeds that nothing in 40k resembles.

I'm not sure how we stand a chance.

Against how many and what? Against the combined might of the all astartes fleets coming to annihilate the planet? Absolutely none. A ground war with a chapter? Over in hours with all marines dead.

40k is Space *FANTASY*, it does not work if you look at it realistically.

Anyone remember the first Iraq "war" with Sadam's hundreds of thousands of troops, tanks that could not move and shoot effectively and his few planes? Now think of the Imperial Guard.

Offhand...

2 Drop Pods to Washington DC. One for the Pentagon, one for the White House / Capital Hill.

One to the UN and New York in general, just to make a point.

Teleport some termies into Cheyenne Mountain. Then lets say another... 6 pods to assorted areas around the US. Chesapeake Bay, some of the big military bases, any Intelligence sites.


Russia and China, probably the same number of Drop Pods as to the states each.

UK... One to London, one to Faslane, Maybe one more, if they've got marines to spare...

So, lets say, 2 companies worth of Space Marines from 2 Strike cruisers., for a single Drop Pod strike.

Would the drop pods be shot down? Presumably a marines enemies do try to do that, so there would be some countermeasures against SAMs, probably jamming like someone mentioned. - Plus, the pods are relatively thickly armoured.

I can't imagine there would be any real marine armoured deployment, there just wouldn't be any point. It would be a matter of "oh flip, the majority of our command and control people have been killed and "we've just been invaded by spacemen!"

After that, the marines would either established Dawn of War style prefab strongholds while the Guard land, or would just simply withdraw.

I may have just thought about this a little too much...

The problem with that is that it would work to decapitate the leadership of the country, but the US is designed for fast and peaceful transfer of power. Kill the President, the VP takes over, killed both, the president pro tempore takes over, etc.. You can kill and cripple a lot of nodes government before it starts to break down. Our system has build in redundancies that are designed to survive a nuclear war, it might take a few hours, but it works.

 Compel wrote:
Offhand...

2 Drop Pods to Washington DC. One for the Pentagon, one for the White House / Capital Hill.

One to the UN and New York in general, just to make a point.

Teleport some termies into Cheyenne Mountain. Then lets say another... 6 pods to assorted areas around the US. Chesapeake Bay, some of the big military bases, any Intelligence sites.


Russia and China, probably the same number of Drop Pods as to the states each.

UK... One to London, one to Faslane, Maybe one more, if they've got marines to spare...

So, lets say, 2 companies worth of Space Marines from 2 Strike cruisers., for a single Drop Pod strike.

Would the drop pods be shot down? Presumably a marines enemies do try to do that, so there would be some countermeasures against SAMs, probably jamming like someone mentioned. - Plus, the pods are relatively thickly armoured.

I can't imagine there would be any real marine armoured deployment, there just wouldn't be any point. It would be a matter of "oh flip, the majority of our command and control people have been killed and "we've just been invaded by spacemen!"

After that, the marines would either established Dawn of War style prefab strongholds while the Guard land, or would just simply withdraw.

I may have just thought about this a little too much...

And if the relevant people aren't at those locations/they are replaceable/etc? The US military wouldn't stop functioning if the pentagon was taken out for instance, they have backup command systems and the regional commands are quite capable of very extended operations on their own provided their supplies hold out.

I'm not sure what drop pods are supposed to do at cheyenne mountain, they can't drop *into* the mountain and they can seal it up against anything short of a direct hit from a nuclear bomb.

So your two or three drop-pods land, and their contents are shortly thereafter targeted and destroyed by bombs/missiles from fixed wing aircraft or engaged by helicopter attack aircraft and/or engaged by overwhelming numbers of conventional troops within minutes, hours at most. Within the pentagon itself, that place is *HUGE*, 10 marines could not secure that building, and it'd take quite a while to kill everyone inside, they'd never be able to get anywhere near everyone because there just aren't enough to cover to be everywhere they'd need to be.

If you want to read a good book on a similar situation, go read John Ringo's "Live Free or Die" on how an attempt to subjugate Earth from space could unfold.The situation is somewhat different, but more likely than a full scale invasion.

I did say "teleport" for Cheyenne. If they're Imperial Fists, they're quite experienced at teleporting into mountains (hehehe).

I don't recall them teleporting into mountains (though I admit my Black Library-fu is weak as of late), but even then, they'd have to know it exists, its significance, and its location, and even then it's a facility that can be quickly sealed and compartmentalized and evacuated/collapsed on itself/reinforced/etc.

I would give Earth like... 30 minutes. 30 minutes plus those few days until the UN council assemble.

Then, hell would break loose quickly, nations would turn against each other, and the people of Earth would tear themselves apart in a massive WW3 deathmatch where everyone wants to prove himself worthy for the goodwill of the galaxy spamming empire. The first Drop Pod would be welcomed by the leaders of the winning nation who would surrender immediaetly with the best conditions (for the invaders of course) in return that the president of the winning nation could be the Imperial Commander of Earth. Civilian unrest would be quickly suppressed by the local authorities (who would call themselves Imperial PDF/Arbites Auxiliria but they would be the same guys as before). And end of story, enjoy your Imperial citizenship in your ruined home (bombed into dust by some random Earth nation).

I doubt if a single bolt shell would be fired. Earth would fall before the SM Strike Cruiser could reach high orbit.

They could just blow it up from orbit in a second, or destroy its cities and simply leave. If they were going to simply attack the planet and leave conquest/pacification/occupation to the Guard, theoretically a single Chapter could probably destroy most of our vital targets & cities from orbit.

But to conquer and hold the planet without backup? Hundreds of thousands minimum. They'd face a vicious guerrilla war and GW has little idea of numbers required for warfare.

 Vaktathi wrote:

 Justicar_Thunderflanks wrote:
How many space marines would it take to conquer the world?
A tactical Squad?
A company?
A chapter?
More?
Your opinion and explanation in the comments. Question was made with vanilla marines in mind, but feel free to include opinion on your favourite chapter.

Not counting the ability to perform Exterminatus?

In all honesty the Space Marines wouldn't last very long. The world's largest militaries have tens of thousands of aircraft and hundreds of thousands of artillery guns combined and tens of millions of soldiers and probably a hundred thousand tanks all told to engage them with, they'd be wiped out in hours. Starships can be engaged with nuclear missiles and 40k has shown they are still potent and forbidden weapons, and the marines are highly limited in number, extremely vulnerable to being surrounded and cut off, have limited aircraft and even more limited AA defense, no heavy artillery, etc. We could engage them from the seas once the SM's landed and they'd have no defense from carrier based aircraft.

Hell, even just a ground war, there's so few that they'd be extremely easy to surround in a pocket and simply blast to pieces with artillery.


Space Marines are Fantasy Knights in Space. From any realistic perspective they just do not function. You cold throw all 1 million space marines at earth and they'd likely all be killed.

 DarknessEternal wrote:

Why would the marines be standing anywhere such weapons could come to bear?

We don't keep any of our important things out in wide open fields. Marines have drop pods and teleportation, for which we have no defense. They would only ever be exactly where our important stuff is.

And they'd know all of that how? And be able to hit all of it simultaneously with sufficient force and speed...how? Drop pods are all well and good, but without knowing where to put them and being able to put enough of them in enough places, they quickly become isolated units easily destroyed through air assets and artillery.

Again, a single Strike Cruiser probably carries more firepower than our combined Nuclear arsenals. They routinely fire torpedoes the size of skyscrapers at their enemy.

As a side-note, nukes are outlawed because they irradiate perfectly good planets, not because they're "too powerful". Look at Krieg, their crime isn't that they blew the living crap out of themselves, it's that the planet is now a radioactive wasteland. In a setting where habitable planets are useful, that's not a good idea.

 AlmightyWalrus wrote:

Again, a single Strike Cruiser probably carries more firepower than our combined Nuclear arsenals. They routinely fire torpedoes the size of skyscrapers at their enemy.

That fire otherwise conventional warheads that are manually loaded into place by chain-gangs of slave crews, likewise the turrets are rotated by chaingangs of slave crews. I'm not saying they couldn't make a mess of things, but to actually conquer (not simply blast it into oblivion) earth by conducting anything but an orbital bombardment from out of range of our rockets/missiles, just isn't possible from any realistic perspective. Hell, their own ships don't work from a realistic perspective even in real-space.

Again, 40k is Space Fantasy, not Science Fiction.

As a side-note, nukes are outlawed because they irradiate perfectly good planets, not because they're "too powerful". Look at Krieg, their crime isn't that they blew the living crap out of themselves, it's that the planet is now a radioactive wasteland. In a setting where habitable planets are useful, that's not a good idea.

They're still powerful enough to destroy a hive world to the point where a single IG regiment and whatever support it was able to drum up was able to then challenge the rest of the planet. They're still very powerful weapons even in the 40 universe.

1 no space marine loyal would step foot on holy terra.
2 six billion humans vs. 1000 marines? Really?

Plus we have nukes knives and sharp sticks. 3 up as isn't gak compared to an atomic weapon or two. Humans have proven when it comes to killing nothing on this planet is more efficient at it than us.

 Vaktathi wrote:

 AlmightyWalrus wrote:

Again, a single Strike Cruiser probably carries more firepower than our combined Nuclear arsenals. They routinely fire torpedoes the size of skyscrapers at their enemy.

That fire otherwise conventional warheads that are manually loaded into place by chain-gangs of slave crews, likewise the turrets are rotated by chaingangs of slave crews. I'm not saying they couldn't make a mess of things, but to actually conquer (not simply blast it into oblivion) earth by conducting anything but an orbital bombardment from out of range of our rockets/missiles, just isn't possible from any realistic perspective. Hell, their own ships don't work from a realistic perspective even in real-space.

Again, 40k is Space Fantasy, not Science Fiction.

The point wasn't that they'd shoot us, but that Strike Cruisers are built to withstand punishment far in excess of what we are capable of dealing out. Those torpedoes are way beyond anything we've ever built. Not to mention the fact that we'd have a hard time hitting them in the first place; between Void Shields, countermeasures and all our satellites being shot down we'd not stand a chance at shooting down a Strike Cruiser as presented in the fluff.

EDIT: Then again, we have the God-Emperor of Mankind.

We have literally tens of thousands of satellites in orbit, and a whole lot of space junk, nobody is shooting them all down, much less determining which do what and picking them out, in any meaningful amount of time

As for void shields and countermeasures, relatively simple macrocannon are described as effective, and those are just upsized conventional cannons, I'm sure nuclear warheads would be effective. The big problem would be targeting, but even near misses result in EMP waves, etc.

 Vaktathi wrote:

 DarknessEternal wrote:

Why would the marines be standing anywhere such weapons could come to bear?

We don't keep any of our important things out in wide open fields. Marines have drop pods and teleportation, for which we have no defense. They would only ever be exactly where our important stuff is.

And they'd know all of that how?

Because that's how they attack. They wouldn't be attacking if they didn't know.

 DarknessEternal wrote:

 Vaktathi wrote:

 DarknessEternal wrote:

Why would the marines be standing anywhere such weapons could come to bear?

We don't keep any of our important things out in wide open fields. Marines have drop pods and teleportation, for which we have no defense. They would only ever be exactly where our important stuff is.

And they'd know all of that how?

Because that's how they attack. They wouldn't be attacking if they didn't know.

the only 3 reasons they know where stuff is in the fluff is because the guard has encountered these threats and has relayed the information, they have been tracking those people for a while, or an inquisitor is able to give them some info..... the enemies of the imperium are not as subtle as we are

Honestly, you can't compare the details of Earth and the details of 40K and make a nice fit. I think that if you want to imagine a space marine invasion, you have to consider what Earth's equivalent would be in 40K.

Now, everything in the Imperium uses las/plasma/other sci-fiish weaponry. You could say that it's just for cool scifi, or you could say that it's because it's vastly superior. In that scale, most of our technology is still at a primitive 'slug-thrower' level. If you consider that a lasgun can't pierce Ork armour, and that our bullets will tear through anything short of specifically designed bullet-proof armour, we start to realise that our good armour is about on par with Orks.

I would estimate a standard earth rifle to be about S2 Ap - range 12-18 if it were balanced to 40K. Our anti-tank weapons probably don't get past S6, with some of our biggest guns maybe Being AP3. Also, I'd say that our big big tanks, are probably only AV10 or 11. Maybe cutting to 12 for the uber-big ones.
Then, if you consider us on the 40K scale, we realise that we're a primitive human world still throwing lumps of metal at each other. By that comparison, I would estimate a single company backed up with some Imperial Guard.

As much as we like to think our guns are big, we need to remember that they're now alot bigger than they were a century ago. How much bigger do you think they got in 40,000 years?

 Vaktathi wrote:
We have literally tens of thousands of satellites in orbit, and a whole lot of space junk, nobody is shooting them all down, much less determining which do what and picking them out, in any meaningful amount of time

As for void shields and countermeasures, relatively simple macrocannon are described as effective, and those are just upsized conventional cannons, I'm sure nuclear warheads would be effective. The big problem would be targeting, but even near misses result in EMP waves, etc.

Lol.

IRL nukes actually are complete garbage compared to the arsenal they have in 40k. Deathstrike missiles are more powerful then the Tsar Bomba, the strongest nuke we have ever made. Deathstrike missiles are inadequate in taking down thing like Titans, let alone space ships. Hell, Macrocannons are capable of more firepower then any nuke we have, we could do absolutely nothing to a strike-cruiser were it to park itself in our orbit.

If space marines came, it wouldn't matter if it was just one I would proclaim my faith in the God Emperor and fight beside him like any true servant of the emperor would. Also if a space marine came then the Emperor would appear and then it would be let the good times roll.

 Vaktathi wrote:

As for void shields and countermeasures, relatively simple macrocannon are described as effective, and those are just upsized conventional cannons, I'm sure nuclear warheads would be effective. The big problem would be targeting, but even near misses result in EMP waves, etc.

Yeah no. You're not gonna get an EMP from a nuke against something outside of the atmosphere. As for the macro-cannons, we don't know how much better than ours the adamantine cores of the rounds fired make them. And, again, who on this planet actually has one of those anyway? Not to mention that we'd get a few shots off and then have it eat a Bombardment-cannon to the knee.

There's also another fault with our nukes: they're not armour piercing. Have fun having the missiles impact the Battle-barge and then do almost no damage at all compared to what a hit from a torpedo would've done, which it's designed to survive.

Cmon guys, exact technicalities are of little importance. If SM force, unsuported by IG, woulddhave to conquer earth...
Conquiring is NO defeating all of the oponent's armies. It is forcing opponent to bow down.
Well, remember how Pizarro conquered huge Inca empire? He did not defeated all their armies, he showed the power and local malcontents, oppressed tribes and much more started joining him,giving inteligence info, supplies and manpower.
We vs Marines = Incas vs Pizarro

Potentially only one, if he was a good enough diplomat.

Does it have to be loyalist marines?

What about all those CSM? Now that would be far more of a challenge, as you know they are much better at these kinds of actions.

 Vaktathi wrote:

 Lobukia wrote:
Why do we know they're coming?

Because we have active surveillance of local space around earth?

Active surveillance can detect ships that are approaching in the Warp? By the time they exit, they're basically on top of us.

Personally, I'd say the Space Marines would lose in many cases for a ground war. I mean, it'd be a tough fight, and many of us would die, but there's a very key reason as to why they'd lose: They aren't there as conquering armies. They aren't there to conquer an entire non-Imperial world on their own. It's not their role, and it hasn't been their role since the Great Crusade.

Conquering is the Imperial Guard's job. The Imperial Guard are there to flatten enemy resistance through a slow, unstoppable hammer of millions or troops, tanks and artillery, with plenty of orbital support. They are the Hammer of the Emperor. The Astartes are the Emperor's Scalpel. Deadly, but not there to smash a planet of enemies to bits.The Astartes' job is crippling key targets and performing surgical strikes, on, say, nuclear weapon depots or major command posts, likely making the Guard's job easier.

But send them in alone without outside Imperial aid? That's like sending the scalpel to cut down a man in armor. The Hammer would be far more easy and effective, especially if the scalpel severed some tendons first. And honestly, given our planet of heretics, launching an actual, full Imperial force wouldn't be out of the question.

 Elector wrote:

 Vaktathi wrote:

 Lobukia wrote:
Why do we know they're coming?

Because we have active surveillance of local space around earth?

Active surveillance can detect ships that are approaching in the Warp? By the time they exit, they're basically on top of us.

Ships don't exit the warp in direct orbit, or anywhere near it generally. They typically emerge at the edge of a system and spend days or weeks moving in.

Personally, I'd say the Space Marines would lose in many cases for a ground war. I mean, it'd be a tough fight, and many of us would die, but there's a very key reason as to why they'd lose: They aren't there as conquering armies. They aren't there to conquer an entire non-Imperial world on their own. It's not their role, and it hasn't been their role since the Great Crusade.

Not to mention that their numbers would be so small they'd be easily surrounded, isolated and destroyed by heavy weapons/artillery/etc (as at the Falaise Pocket) with attempts at break out easily countered given their limited numbers.

 AlmightyWalrus wrote:


Yeah no. You're not gonna get an EMP from a nuke against something outside of the atmosphere.

Huh? That's where they're actually at their most effective. Blast is what isn't going to affect things as much outside and atmosphere, the EMP is significantly more effective from a nuclear blast when it doesn't have an atmosphere to deal with.

As for the macro-cannons, we don't know how much better than ours the adamantine cores of the rounds fired make them.

They're still basically big cannons, that can all be calculated theoretically, and unless the density of adamantium is mind-bogglingly greater than anything imagineable today, nuclear weapons could match them.

And, again, who on this planet actually has one of those anyway? Not to mention that we'd get a few shots off and then have it eat a Bombardment-cannon to the knee.

Bombardment cannons have limits, Vraks alone, a world of a mere 8 million souls, the vast majority of which were laborers, with anti-orbital defenses only around one limited area, was strong enough that no Space Marine chapter would take on the job until the Imperial Guard had been fighting for years and was able to present a greater threat to SM ships that bombardment would back. Against a world with thousands of scattered and hidden launch sites, I wouldn't worry about it.

There's also another fault with our nukes: they're not armour piercing.

...they don't need to be.

Have fun having the missiles impact the Battle-barge and then do almost no damage at all compared to what a hit from a torpedo would've done, which it's designed to survive.

40k Torpedos are packed with conventional explosives that detonate on impact, and are big enough on their own that by any realistic perspective would be easily intercepted and destroyed. A nuclear missile packing half a dozen multi-megaton warheads on MIRV launcher the size of a commuter car would be significantly more dangerous. Again, 40k is space fantasy, it doesn't actually work when looked at realistically.

 Aun Tier wrote:
Honestly, you can't compare the details of Earth and the details of 40K and make a nice fit. I think that if you want to imagine a space marine invasion, you have to consider what Earth's equivalent would be in 40K.

Now, everything in the Imperium uses las/plasma/other sci-fiish weaponry. You could say that it's just for cool scifi, or you could say that it's because it's vastly superior. In that scale, most of our technology is still at a primitive 'slug-thrower' level. If you consider that a lasgun can't pierce Ork armour, and that our bullets will tear through anything short of specifically designed bullet-proof armour, we start to realise that our good armour is about on par with Orks.

I would estimate a standard earth rifle to be about S2 Ap - range 12-18 if it were balanced to 40K. Our anti-tank weapons probably don't get past S6, with some of our biggest guns maybe Being AP3. Also, I'd say that our big big tanks, are probably only AV10 or 11. Maybe cutting to 12 for the uber-big ones.
Then, if you consider us on the 40K scale, we realise that we're a primitive human world still throwing lumps of metal at each other. By that comparison, I would estimate a single company backed up with some Imperial Guard.

As much as we like to think our guns are big, we need to remember that they're now alot bigger than they were a century ago. How much bigger do you think they got in 40,000 years?

So you're saying our heavy tanks are about as tough as an ork buggy or killa kan and that this http://en.wikipedia.org/wiki/M829_(munition)#Variants.23M829A2 can't penetrate terminator armour?
I think you're severely overestimating Imperial gear.

BlaxicanX wrote:
With a ship in orbit any number of space marines could probably conquer us pretty easily.

On the ground, though, if they can't rely on deepstriking/teleporting into important places (read: the pentagon, various capitals etc), they eventually just get killed to death by superior firepower.

Space Marines are deadly against a squad of dudes armed with small arms, but a single helicopter armed with armor piercing weaponry would make short work of a Space Marine. We have way more helicopters, and jets, and artillery, and basically weapons that can one-shot a Marine, than a chapter has marines.

Not to mention tactical nukes. I've always found the lack of tactical nukes in a universe that uses virus bombs and cyclonic torpedoes to be less than believable.