Pre-Heresy Imperium vs Galactic Empire

[Lord_Of_Change 9]

Not sure if this has been done before, checked the search function but still not certain, so apologies if it has been done. So, anyway, the scenario. A portal opens between the Tatooine system in the Star Wars galaxy and the Prospero system in the 40K Milky Way. The timeframe for Star Wars is just after the completion of the first Death Star, and for 40K just before the Emperor chastised Lorgar on Monarchia. Palpatine decides that this new galaxy is ripe for conquest, and sends his forces through the portal. Before long, it becomes a full-scale war.

Rules for this debate:

SW humans have minimal Warp presence, like the Tau.

The God-Emperor of Man is not going to be directly aiding the Imperium.

Chaos holds off on corrupting the Primarchs for right now.

So, who wins?

[Elheru Aran]

I believe the usual result in 40K vs. SW is "40K can take the ground but SW will take space and ultimately win".

Throwing the Primarchs and the Imperium pre Heresy is definitely... different, though. The Space Marine Legions are going to be pretty damn hard against the Empire on the ground, and they've got all their Titan Legions, super-heavy tanks, etc...

Space is another story though, but with the Imperium's entire fleet at their disposal rather than halved by conversion to Chaos, that's going to be interesting again. However, in general SW demonstrates better acceleration, shields, and more powerful weapons as far as I understand; SW most definitely has better FTL.

The SW humans not having Warp presence isn't that important; any Librarians in the Marines' numbers are going to be able to squish 'em just fine.

Really, seeing as it's the Empire actually venturing into the 40K galaxy, I'd say the Warp gives 40K the edge somewhat unintentionally. "Captain, hide us in that funny looking bit of space....what in the world are these things coming through the walls?!"

[Simon_Jester]

One thing to factor in is that the Imperium's technology pre-Heresy was, on average, better. There were more surviving relics of the high water mark of human civilization (some time between the 22nd and 25th millenia), and there were more examples to go around of the high-end stuff produced by the Imperial war machine.

From 30000 to 40000, some specific aspects of the hardware improve, but the availability declines badly for high-end equipment.

[Juubi Karakuchi]

The GE's success depends heavily on being able to secure the Prospero system, at least at the early stages. The IOM's best chance of success is to prevent the GE getting a firm foothold and clogging the plot wormhole.

Unfortunately for the GE, Prospero happens to be one of the pre-Heresy Imperium's tougher nuts to crack. Details of the defences come from 'A Thousand Sons', in which Prospero is described as possessing orbital defence platforms (which Magnus blinded with his powers), and the existence of ground-based weapons is implied. The cities themselves are protected by 'kine-shields' which prove capable of resisting the Space Wolves bombardment, itself described as destroying 'whole swathes of mountains' and 'levelling entire peaks'. A lance beam is described as hitting the ocean bay near Tizca (the planetary capital) turning a 'five hundred metre column of seawater to superheated steam', which then drifts in over the docks and scalds the workers to death. The city is otherwise unaffected.

The main strength of the defence lies with the Thousand Sons themselves. They are Astartes, with a higher than average proportion of psykers. They number in the single-digit thousands IIRC before their destruction, of which a significant number would be on Prospero at any one time. Their psychic powers are divided into five specific disciplines, each practiced by one of five cults. The Athanaeans specialise in telepathy, performing communications and intelligence roles. The Corvidae specialise in precognition, both tactically and strategically. The Pavoni specialise in physiokinesis (manipulation of bodily processes, also called biomancy). They are not only good healers (beyond what Apothecaries are capable of), but can use their bioelectricity offensively (essentially Force Lightning), and mess with their enemies' bodies (making blood boil, hearts explode, etc). The Pyrae can generate and control fire, both projecting it offensively and protecting themselves from it. Their portfolio also includes controlling machines, such as robots and titans, and possess a single Warlord Titan named Canis Vertex, which one of them can control via astral projection. The Raptora specialise in telekinesis, both offensive and defensive (think Tetsuo Shima if he ever became a Space Marine).

As for conventional capabilities, there is the Prospero Spireguard. These are essentially Imperial Guard (Imperial Army at the time) in terms of equipment and training. One little extra is disc-shaped two-man skimmers, armed with 'heat-lances' and missile pods, controlled by the Spireguard Air Command. I don't have any information on their numbers.

Any ground campaign to take the planet will be a long-winded and painful affair. If the Force and Psychic powers are in no way related (implied by the scenario rules), then the GE has no way of knowing or understanding what it is dealing with. As such, were they to try and bombard the kine-shields, the GE commanders would likely conclude they were dealing with something approximating to their own shield technology. TESB shows that GE doctrine is not to bombard a theatre shield. As such, they would have to find somewhere to land their ground forces. Prospero's population is described as living in a small number of cities, around which ground defences would most likely be clustered for maximum protection. Defence lasers are described in the Battlefleet Gothic Rulebook as having ranges in the hundreds of miles, meaning the GE would have to find landing sites at least 1-2000km away from the cities for its heavy landers. Aside from Thousand Sons counter-attacks, another big problem once on the ground would be the Psychneuein, of which Prospero suffers from a severe infestation (hence the population's preference for living in the cities, which are protected). Psychneuein are non-Chaotic warp manifestations, essentially very large, very intelligent psychic wasps. The females like to lay their eggs in the brains of psykers, though they don't limit their attacks to psykers, being meat-eating predators.

The GE could take Prospero eventually, so long as it can keep the planet isolated and maintain a continuous flow of supplies and reinforcements. If the siege drags on for more than a few weeks, IOM forces will turn up in numbers to drive the GE forces out.

[Simon_Jester]

Do the native psychics on the planet have any ability to interfere with orbiting starships? Say, to mind-control admirals into giving bad orders, or gunners into firing on friendly troops? Are there surface-to-space weapon emplacements of meaningful firepower by 40k standards of "meaningful firepower?" How strong are those defense platforms?

[Black Admiral]

Do the native psychics on the planet have any ability to interfere with orbiting starships? Say, to mind-control admirals into giving bad orders, or gunners into firing on friendly troops?

If Magnus is present, he could certainly do so. THe other Prosperine sorcerers, not sure; it's certainly within the implied capabilities of the likes of Ahriman but I don't know if they've ever actually done anything like that.

Are there surface-to-space weapon emplacements of meaningful firepower by 40k standards of "meaningful firepower?" How strong are those defense platforms?

Unknown about Prospero's - we know they exist, but the entire defence grid, "from outer orbital to close surface" (Prospero Burns, pg. 401) (with the exception of the individual city shields, and it's standard procedure to have them up at all times) was stood down by Magnus - but judgements can be made based on the defences of Fenris (since the Astartes Legions' homeworlds are apparently all defended on a similar scale). Battle of the Fang describes those; not counting the Wolves' fleet, Fenris has two layers of orbital defence platforms, and the batteries and shields of the Fang itself. Between them (and with some degree of warning, which the Thousand Sons were able to negate in their attack on Fenris in M32), they're expected to stand off a fleet four times the size of the one (fifty-four capital ships and hundreds of escorts, including a pair of specialised planetary bombardment ships) the Thousand Sons brought to bear.

[Lord_Of_Change 9]

Magnus is not present on Prospero for the purposes of this debate.

[Juubi Karakuchi]

The only information I have on the Defence Laser comes from the Apocalypse Datafax, which describes it as being able to shoot into low orbit (fitting the hundreds of miles figure given in the BFG rulebook) and that even a glancing hit can drive off anything up to a cruiser once its shields are down. Other ground defences listed in the BFG rulebook include torpedo silos (essentially the same as ship-mounted torpedoes, but fired from the ground), and attack craft (fighters and bombers).

Unknown about Prospero's - we know they exist, but the entire defence grid, "from outer orbital to close surface" (Prospero Burns, pg. 401) (with the exception of the individual city shields, and it's standard procedure to have them up at all times) was stood down by Magnus - but judgements can be made based on the defences of Fenris (since the Astartes Legions' homeworlds are apparently all defended on a similar scale). Battle of the Fang describes those; not counting the Wolves' fleet, Fenris has two layers of orbital defence platforms, and the batteries and shields of the Fang itself. Between them (and with some degree of warning, which the Thousand Sons were able to negate in their attack on Fenris in M32), they're expected to stand off a fleet four times the size of the one (fifty-four capital ships and hundreds of escorts, including a pair of specialised planetary bombardment ships) the Thousand Sons brought to bear.

On the basis of size, the Imperium would consider an ISD a large escort (up to 2km in length), and an SSD a very large battleship. Assuming approximate parity in firepower, Prospero's defences should be able to fight off many hundreds, even thousands, of GE warships.

[J Ryan]

The only information I have on the Defence Laser comes from the Apocalypse Datafax, which describes it as being able to shoot into low orbit (fitting the hundreds of miles figure given in the BFG rulebook) and that even a glancing hit can drive off anything up to a cruiser once its shields are down. Other ground defences listed in the BFG rulebook include torpedo silos (essentially the same as ship-mounted torpedoes, but fired from the ground), and attack craft (fighters and bombers).

Unknown about Prospero's - we know they exist, but the entire defence grid, "from outer orbital to close surface" (Prospero Burns, pg. 401) (with the exception of the individual city shields, and it's standard procedure to have them up at all times) was stood down by Magnus - but judgements can be made based on the defences of Fenris (since the Astartes Legions' homeworlds are apparently all defended on a similar scale). Battle of the Fang describes those; not counting the Wolves' fleet, Fenris has two layers of orbital defence platforms, and the batteries and shields of the Fang itself. Between them (and with some degree of warning, which the Thousand Sons were able to negate in their attack on Fenris in M32), they're expected to stand off a fleet four times the size of the one (fifty-four capital ships and hundreds of escorts, including a pair of specialised planetary bombardment ships) the Thousand Sons brought to bear.

On the basis of size, the Imperium would consider an ISD a large escort (up to 2km in length), and an SSD a very large battleship. Assuming approximate parity in firepower, Prospero's defences should be able to fight off many hundreds, even thousands, of GE warships.

Fenris is an exception rather than the rule though, as it was stated as perhaps being the 2nd most defended world after Terra. Of course Prospero's defences may not be as good as Fenris, but they are still nothing to sniff at, and starting your beachhead at a Legion homeworld is probably not the best idea. The GE fleet would do better at using their FTL advantage to leave the system ASAP and create a staging area at a less developed world.