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Alrighty folks, next up in the faction wars is the Imperium vs the Tyrinids.
Assumption -
No other interference, imperium has access to EVERYTHING, this includes but is not limited to
Titan legions
All adeptus Astartes
Entire Inquisition
Admech tech
All assassins
Sisters of battle
The Grey knights
Over arching command goes to Creed, with chapter masters
Dante, Azreal, and Calgar, taking up command positions in field.
These are basically the strategic minds of the imperium. Though if need be will gladly enter the field of battle.
other chapter masters and the like operate as a more field oriented role of leadership.
No falling to chaos
The nids-
Have access to all hive fleets
are NOT endless in number, they can have numbers that rival orks, but not endless just to put to rest the "countless more fleets are yet to reach " argument.
Genestealer cults are active.
Lets remember some things-
Please use citations for arguments involving fluff
(Ie working of a weapon to talent of a command/skill in battle)
Please follow rule 1 of dakka forums.
If you are not going to cite information, do not present it as facts. If you cannot remember a page number/not on internet just leave the name of the book you read. All codex citations should have page numbers or at least a reference.
Keep the amount of fanboy arguing to a minimum, as this lead to breaking of rule 1 in the last thread.
Most of all, please enjoy the debate, and have fun!
If the IoM has all of their resources able to be put against this, they've got it covered. The reason the IoM is failing is because it's being attacked on all sides constantly, and it still makes victories like that. Granted, the nids will be scary still, but I don't think they can win, unless they just throw IG at them until the nids are triple the size from that. I voted for nids, but I made the mistake of not reading the description for, and I assumed it meant "IoM (in its actual state) vs Nids (IE more would show up)" so I messed up with that.
All in all, it will be a very hard battle, but I believe the IoM would pull through.
Irishpeacockz-Blackjack needs a pay raise for being the welcomer to the crusade
Palleus-Write a school essay about Kroot! Pride. Prejudice. And Cannibalsim.
All known hive-fleets united VS imperium with 0 other threats to worry about, no infinite more Tyranids on the way?
Yeah, that goes to IoM no problem. The only "issue" will be splinter-fleets after the main push has been defeated, but even those will still be dealt with after enough time.
If not distracted by other threats I'd put my money on IoM. The speed in which the body count would stack up on both sides would be pretty juicy but the currently known fleets would run out before the IoM would. It would be a victory through attrition.
I also voted for IoM.
Tyranid's strength is also their weakness. Only way I see to defeat them would be to contain and starve them. Evacuate planets in the tendrils path/reach and virus bomb them to destroy all biomass. Divert the industrial resources used for planetside war and produce more spaceships with fewer crew and more guns.
Use Space Marines and Titans to eventually purge planets that had Tyranid infestations, after the tendrils have been eliminated.
Forgot to also include the AdMech, since they are more machine then organic.
This message was edited 1 time. Last update was at 2015/07/08 07:20:00
I did a thought experiment on numbers a while back. So basically Nids assuming my math was correct
Spoiler:
So lets begin with the Nids.
In the BRB there is a passage on the Hive Fleets (sub box page 237) which states there have been 9 distinct Hive Fleets in the Galaxy thusfar with "millions" of ships comprised of "mililons" of creatures ready for invasion.
Taking the lowend numbes first that would give us:
9 x 2,000,000 (2 million) x 2,000,000 (2 million)
Im taking 2 million as the very lowest end as the word "millions" implies more than one.
Hence, that totals:
3.6 to the power of 13.
That equals 360 trillion.
Next we take the extreme upper end. Since millions implies more than 1, the Nid fleets could reach a cap of 999,999,999 (or nine hundred and ninety nine million). So could the creatures onboard (as per the passge quoted).
There are 9 distinct fleets.
Hence
9 x 999,999,999, x 999,999,999
= 9 to the power of 18 which is called 9 quintillion afaik (9,000,000,000,000,000,000).
So thats the known Nids upper and ower ends. Obviously the other fleets int he Galactic Void and elsewhere could be even larger than this (or smaller too) but there is no hard evidence on them at all from what I can see.
Next is Humanity - I havent tried to do the Imperial Guard as the numbers are hard to pin down.
It is quoted in the BRB (page 170) that Humanity numbers around 1 million worlds. It also states this could be more or less due to the inherent inefficencies of tracking all the worlds so lets take the 1mil mark as a good base.
This is where things get less clear imo though.
Wiki quotes the IoM as having 32,380 Hive worlds. Each world can have 5-20 Hives with populations ranging fro 10 to 100 billion.
http://warhammer40k.wikia.com/wiki/Planets
Personally Im unsure of where these numbers came from but lets try them out to see.
Lets start with the lower end for Hive worlds.
32,380 x 5 (hives) x 10,000,000,000 (10 billion)
= 1.6 to the power of 15 or 1.6,000,000,000,000,000)
or 1.6 quadrillion in short hand.
Things get difficult here however as there are no hard numbers for the other types of IoM worlds, civilised, fuedal, forge, death, agri, death etc.
Sticking with the low end figures fuedal worlds are stated to have a min population of about 10,000,000.
So taking 1,000,000,000 (total worlds) minus 32,380 (the Hives) leaves us with 967,620 worlds.
967,620 x 10,000,000 = 9.6 to the power of 12 or 9.6,000,000,000,000
or 9.6 trillion (note not even a patch on the Nid lowend numbers).
High end IoM then:
High end Hive
32,380 x 20 (hives per world) x 100,000,000,000 (100 billion)
= 6.5 to the power of 15 or 6.5,000,000,000,000,000
or 6.5 quadrillion
Taking the remaining 967,620 worlds and maxing all of them below a Hive worlds cap 99 billion (acknowledged this is wacky and dosent fit with feral, fuedal worlds) gives:
967,620 x 99,000,000,000
= 9.57 to the power of 16 or 950,000,000,000,000,000
or 950 quadrillion
+ Hives = 956 quadrillion.
Note still nowhere near the Nid upper levels.
Finally we can do an extreme IoM and say 1 millio worlds by the Hive cap of 100 billion
1 million x 100 billion=
1 to the power of 17
or 100,000,000,000,000,000
100 quadrillion.
About one tenth of the Nid population.
Dman137 wrote:
goobs is all you guys will ever be
By 1-irt: Still as long as Hissy keeps showing up this is one of the most entertaining threads ever.
Well if the psykers aren't held back, you'll have guys like Dak'ir just shredding Hive Fleets in a similar fashion to Maugan Ra with little effort. The main thing constraining the Imperium is Chaos... without that it's open season on Tyranids as humans can utilize their psychic powers without restraint. Alpha Psykers in general will just go to town and reap trillions.
Also then there's other things, like the legions of Imperial Daemons besieging the Eye of Terror now pursuing new targets (good luck fighting avatars of fire), the Legion of the Damned. and most importantly areotech. If the Admech starts pumping out more DAOT tech, the Imperium will put the hurt on the Nids hard, especially in space.
This message was edited 2 times. Last update was at 2015/07/09 07:44:35
“There is only one good, knowledge, and one evil, ignorance.”
"millions" of ships comprised of "mililons" of creatures ready for invasion.
is fine, but 9 x 2,000,000 (2 million) x 2,000,000 (2 million) implies each of those two million ships in a fleet has two million warrior-forms aboard. The boxout wording isn't necessarily stating that; even the assumption that it's stating each fleet is 2 million plus is not confirmed, and - since hive ships are of a similar scale to imperial capital ships, which have a crew population in the tens or hundreds of thousands (see Rogue Trader or novels like Resolute/Relentless), then having a 'troop complement' in the millions is unlikely.
Millions of warrior forms held in 'spore readiness', maybe, but that's not ready troops - youve got to sieze biomass to make them into actual combat units.
I'd concur that an otherwise undistracted Imperium Of Man would be capable of slapping down any threat currently described (disregarding ancient, sleeping necrons, currently-in-the-void hive fleets, and disunited ork empires). What makes it threatened is all of the dangers happening at once.
but 9 x 2,000,000 (2 million) x 2,000,000 (2 million) implies each of those two million ships in a fleet has two million warrior-forms aboard. The boxout wording isn't necessarily stating that;
Granted, its likely those ships have very much less than 2 million aboard them. However the math is based on the number ranges given, its simply impossible to say without more detail from fluff which I couldnt find tbh and likely is nowhere to be found outside of fanfic stuff.
The 2mil (+) aboard each ship was based on the number ranges quoted - not an exact science Im afraid.
I'd still wager however Nid numbers are collasol, there was also that 4th/5th IG codex quote that stated IG military preparation would have to ramp to 500% of current to meet a full scale Nid invasion. Until we get a hard number on what the current IG military forces look like its still a bit vague but they're going to be big numbers.
Dman137 wrote:
goobs is all you guys will ever be
By 1-irt: Still as long as Hissy keeps showing up this is one of the most entertaining threads ever.
Seems to be a lot less debate on this one. That's both good and bad I guess.
Id like to point out that imperial worlds could be chosen as bait.
It wouldn't be hard at leaat first or second time, to lure the nids to a lush, organic enriched world, and let them swarm it and exterminatus it.
That said, imperium would need space superiority and while quite capable of doing so, would assuredly take losses.
Also, on the upper end of power, it is, cannoncily possible to discover a toxin that is incredibly deadly to the hive fleet. (Dawn of war 2) that upon consumptiom could quite possibly kill the entire hive that recives it. Of course this seems to require the hive fleet already be eating said planet. And does nothing for bugs on the ground or not around the hive minds ship.
Ive also heard of an instance where an imperial battle barge kamakazied into a large need fleet, forced its reactor to go critical and took almost a large portion of the tendrils ships. I cant site this one due to bad memory, but if anyone knows what I am talking about please do share.
Another note, nids are all combat ready, only about 75-80% of the Imperium can say the same. IIRC the numbers from the codex correctly - again, just going off memory
Wyzilla wrote: Well if the psykers aren't held back, you'll have guys like Dak'ir just shredding Hive Fleets in a similar fashion to Maugan Ra with little effort. The main thing constraining the Imperium is Chaos... without that it's open season on Tyranids as humans can utilize their psychic powers without restraint. Alpha Psykers in general will just go to town and reap trillions.
Also then there's other things, like the legions of Imperial Daemons besieging the Eye of Terror now pursuing new targets (good luck fighting avatars of fire), the Legion of the Damned. and most importantly areotech. If the Admech starts pumping out more DAOT tech, the Imperium will put the hurt on the Nids hard, especially in space.
Imperial Daemons? What?
To quote a fictional character... "Let's make this fun!"
Tactical_Spam wrote: There was a story in the SM omnibus where a single kroot killed 2-3 marines then ate their gene seed and became a Kroot-startes.
Wyzilla wrote: Well if the psykers aren't held back, you'll have guys like Dak'ir just shredding Hive Fleets in a similar fashion to Maugan Ra with little effort. The main thing constraining the Imperium is Chaos... without that it's open season on Tyranids as humans can utilize their psychic powers without restraint. Alpha Psykers in general will just go to town and reap trillions.
Also then there's other things, like the legions of Imperial Daemons besieging the Eye of Terror now pursuing new targets (good luck fighting avatars of fire), the Legion of the Damned. and most importantly areotech. If the Admech starts pumping out more DAOT tech, the Imperium will put the hurt on the Nids hard, especially in space.
Imperial Daemons? What?
The Legion of the Damned. They are, for all intents and purposes, daemons born of the Emperor.
Wyzilla wrote: Well if the psykers aren't held back, you'll have guys like Dak'ir just shredding Hive Fleets in a similar fashion to Maugan Ra with little effort. The main thing constraining the Imperium is Chaos... without that it's open season on Tyranids as humans can utilize their psychic powers without restraint. Alpha Psykers in general will just go to town and reap trillions.
Also then there's other things, like the legions of Imperial Daemons besieging the Eye of Terror now pursuing new targets (good luck fighting avatars of fire), the Legion of the Damned. and most importantly areotech. If the Admech starts pumping out more DAOT tech, the Imperium will put the hurt on the Nids hard, especially in space.
Imperial Daemons? What?
The Legion of the Damned. They are, for all intents and purposes, daemons born of the Emperor.
We've only seen isolated incidents of the Legion of the Damned, what evidence is there that there are "legions" of them?
To quote a fictional character... "Let's make this fun!"
Tactical_Spam wrote: There was a story in the SM omnibus where a single kroot killed 2-3 marines then ate their gene seed and became a Kroot-startes.
I think the combined military might of all Imperial forces and all their dakka-dakka would be enough to win the day, eventually. It would be messy as feth, but I think they'd pull through.
Homebrew Imperial Guard: 1222nd Etrurian Lancers (Winged); Special Air-Assault Brigade (SAAB)
Homebrew Chaos: The Black Suns; A Medrengard Militia (think Iron Warriors-centric Blood Pact/Sons of Sek)
Wyzilla wrote: Well if the psykers aren't held back, you'll have guys like Dak'ir just shredding Hive Fleets in a similar fashion to Maugan Ra with little effort. The main thing constraining the Imperium is Chaos... without that it's open season on Tyranids as humans can utilize their psychic powers without restraint. Alpha Psykers in general will just go to town and reap trillions.
Also then there's other things, like the legions of Imperial Daemons besieging the Eye of Terror now pursuing new targets (good luck fighting avatars of fire), the Legion of the Damned. and most importantly areotech. If the Admech starts pumping out more DAOT tech, the Imperium will put the hurt on the Nids hard, especially in space.
Imperial Daemons? What?
The light of the Astrnomicon spawns legions of angels of fire that besiege the outer worlds of the Eye of Terror and purge all life upon them.
“There is only one good, knowledge, and one evil, ignorance.”
Wyzilla wrote: Well if the psykers aren't held back, you'll have guys like Dak'ir just shredding Hive Fleets in a similar fashion to Maugan Ra with little effort. The main thing constraining the Imperium is Chaos... without that it's open season on Tyranids as humans can utilize their psychic powers without restraint. Alpha Psykers in general will just go to town and reap trillions.
Also then there's other things, like the legions of Imperial Daemons besieging the Eye of Terror now pursuing new targets (good luck fighting avatars of fire), the Legion of the Damned. and most importantly areotech. If the Admech starts pumping out more DAOT tech, the Imperium will put the hurt on the Nids hard, especially in space.
Imperial Daemons? What?
The light of the Astrnomicon spawns legions of angels of fire that besiege the outer worlds of the Eye of Terror and purge all life upon them.
Source? This seems like a really cool piece of fluff, I'd love to read some of the lore behind it
To quote a fictional character... "Let's make this fun!"
Tactical_Spam wrote: There was a story in the SM omnibus where a single kroot killed 2-3 marines then ate their gene seed and became a Kroot-startes.
Talon of Horus, I believe. This was shamelessly lifted from another discussion on the subject over on B&C.
Immersturm wrote:
For those who are interested, here is the passage I am talking about:
Quote
There, sat in placid splendour on my throne, was the ghost of a murdered god.
The god’s face was covered by a mask of shining gold, its features wrenched into a rictus of crying torment. The expression – eyes open, mouth wide, even the parted teeth showing in detailed gold – was a man’s death-scream immortalised in holy metal. Bladed sunrays flared from the edges of the metal face, forming a crest of golden knives.
The rest of his manifestation existed in contrast to the dark ostentation of his sacred helm. He was thin, cadaverously so, and wearing a plain toga of imperial white. His skin didn’t commit to paleness or duskiness – it seemed a caramel blend of both, perhaps born from genetics, perhaps stained by the light of a natural sun.
Quote
‘You are the Astronomican,’ I said.
The golden mask tilted in a nod. ‘I stare into eternity and witness the dance of daemons. I sing forever into the endless night, adding my melody to the Great Game. I am Imperious, the Avatar of the Astronomican. I have come to ask you to turn back.’
Quote
‘You are harming my crew,’ I said to the Solar Priest. ‘These mortals cannot understand your words, and your power wounds them.’
‘I have come as the Voice, not as the Warlord. Harm is not my intent.’
After the Heresy, the Traitors are essentially trapped inside the Eye of Terror. They don't yet have any known safe passage back to realspace.
The protagonists of the novel are looking for the Vengeful Spirit (Horus's flagship),which they've been led to believe is hidden somewhere in the Eleusinian Veil - the dust cloud and crone worlds marking the edge of the Eye. To get there they have to traverse the Firetide.
Where the light of the Astronomican meets the Eye is called the Firetide - like an immense Warp storm crossed with an epic daemonic battle between the Neverborn of the Eye and fiery angels manifest from the Astronomican.
It's this that's keeping the Traitor Legions bottled up in the Eye. Beyond the Firetide are the Radiant Worlds - planets that are bathed in the light of the Astronomican but not burned by it.
They plan to bypass the Firetide using a deserted section of the webway. When they leave it, Imperious shows up to warn them off. He's a daemon, to all intents and purposes - a Warp entity created by the psychic energy of the Astronomican. He tells them continuing on this path (which ultimately results in them finding Abaddon and founding the Black Legion) will lead to the end of the Imperium and the damnation of mankind. That goes down well: Lheor, a World Eater, shoots him.
In 40k rule terms, he would be daemonic character, maybe a herald or even a greater daemon. The essence of the Emperor's will personified in the Warp. In that instance he was an emissary, sent to try to talk to them out of it. But he suggests that if they ignore him, next time they meet he will come as "fire and fury":
Quote
‘My place is to ask you to turn back, and so I ask it once more.’
We looked at each other, we warriors from a handful of rival Legions, not understanding the spirit’s words.
‘Why?’ asked Telemachon. His face mask was a visage of serenity opposing the Solar Priest’s image of wracking pain. ‘What threat are we to you?’
‘You are no threat to me, for I am simply a bridge in the Song. You are a threat to the Singer.’
‘And if we don’t turn back?’ Lheor asked.
‘Then the Song’s next verse will be fire and fury, not wisdom and mercy. It will come – not now, not soon, but in time and in force. The Fate you seek to engineer cannot be allowed to come to pass.’
This message was edited 2 times. Last update was at 2015/07/09 20:42:31
"That time I only loaded the cannon with powder. Next time, I will fill it with jewels and diamonds and they will cut you to shrebbons!" - Nogbad the Bad.
Space Marines: Jacks of all trades yet masters of GRAV CANNONS!!!.
My Star Wars Imperial Codex Project: http://www.dakkadakka.com/dakkaforum/posts/list/641831.page It has 7 HQs, 2 Troop types with Dedicated Transports, 5 Elite units, 5 Fast Attack units, 6 Heavy Support units, 2 Formations with unique units not in the rest of the codex, and 2 LOW choices.
‘I do not care who knows the truth now, tomorrow, or in ten thousand years. Loyalty is its own reward.’ -Lion El' Jonson
I'm assuming that the Legion of the Damned are the Angels of Fire, the ones keeping the Traitor Legions bottled up in the eye. Perhaps the Emprah turns the spirits of heroic Astartes into his Legion of the Damned/ Angels of Fire? they really need to expand upon this and make LotD a full-fledged faction in 40k.
To quote a fictional character... "Let's make this fun!"
Tactical_Spam wrote: There was a story in the SM omnibus where a single kroot killed 2-3 marines then ate their gene seed and became a Kroot-startes.
2BlackJack1 wrote: If the IoM has all of their resources able to be put against this, they've got it covered. The reason the IoM is failing is because it's being attacked on all sides constantly
I agree. The Imperium is extremely powerful, but the problem is that they're a target for every other serious threat in the galaxy - Orks, Necrons, Tyranids, Chaos. Excepting Chaos, arguably, in the long-term sense, any one of these threats is not enough to seriously damage the Imperium, and they only get as far as they do because the Imperium is diffuse and distracted. Any one of them could be eradicated by the Imperium if the Imperium were able to concentrate on eliminating them and managed to coordinate its efforts to do so.
The Imperium reminds me of many historical states that were clearly the dominant power in their region without being totally so. The late Roman Republic, for instance, in its last century or so was frequently at war, but after the conclusion of the Punic Wars it never truly faced an external threat to its existence. The wars against Mithridates VI of Pontus and the Germanic tribes invading northern Italy were serious conflicts, but they were threats to Roman domination of their world, not to the continued existence of the Roman civilisation. The only real threats Rome faced in this period were civil wars.
I think the Imperium is similar. The Orks or the Tyranids can threaten thousands of worlds, maybe even take control of an entire segmentum if not properly checked, but they're no real threat to the continued existence of the Imperium as a whole.
DoomShakaLaka wrote:That is epic. Why can't THEY be a faction?
There is a pretty good reason. Right now, you can see lots of Imperial daemons. At the moment you can read about Gaunt meeting an elderly nun who used to be a soldier and loans him her car, and then later it turns out she has been dead for 2000 years. There is an imperial saint leading a host of guardsmen who is kind of a fake, except that she kind of isn't, and it turns out miracles do happen. The background for Dante is that he was really in the doghouse and threw himself into the fire, but he was blessed by the Sanguinor and now he is who he is. If your palatine dies, (it used to be that) you get more faith points for her army to avenge her.
But if the 40k sigmarines become a faction, then all you have are a bunch of chumps. The models aren't going to actually radiate fire that burns but does not consume. It would just be dumb.
I'm assuming that the Legion of the Damned are the Angels of Fire, the ones keeping the Traitor Legions bottled up in the eye. Perhaps the Emprah turns the spirits of heroic Astartes into his Legion of the Damned/ Angels of Fire? they really need to expand upon this and make LotD a full-fledged faction in 40k.
The Legion of the Damned didn't exist at the time that novel is set.
Imagine the imperium as is. In a 1 on 1 grudge match, you would slowly see the imperium building up the outer perimeter or perhaps a distance within to create a defensive region of systems for safety. What most likely would occur is that Mars would eventually come up with a way to detect tyranid encroachment. Tyranids, as much as I love them, have a fatal flaw when it comes to transportation. Their ability to move through space is dependant on the distance of nearby celestial bodies. When the gravitational forces react with their fleets, it shunts them out quite a ways from their intended targets, and using traditional sublight propulsion, they can be years or even decades away from attacking their target if the system is large enough.
So, what you would see would be the creation of large integrated defense screens designed to detect Tyranids as well as destroy them through the use of orbital defense guns. As long as the fleet is not too massive, the odds of Tyranids reaching the ground are slim, and it would also make the use of large fleets relatively pointless unless a fleet manages to enter the imperium on a new axis where defenses are limited, and a rapid remobilization of firepower is required.
Also, phone autocorrect sucks.
This message was edited 2 times. Last update was at 2015/07/10 18:55:19
"There is a cancer eating at the Imperium. With each decade it advances deeper, leaving drained, dead worlds in its wake. This horror, this abomination, has thought and purpose that functions on an unimaginable, galactic scale and all we can do is try to stop the swarms of bioengineered monsters it unleashes upon us by instinct. We have given the horror a name to salve our fears; we call it the Tyranid race, but if is aware of us at all it must know us only as Prey."
Hive Fleet Grootslang 15000+
Servants of the Void 2000+
Imagine the imperium as is. In a 1 on 1 grudge match, you would slowly see the imperium building up the outer perimeter or perhaps a distance within to create a defensive region of systems for safety. What most likely would occur is that Mars would eventually come up with a way to detect tyranid encroachment. Tyranids, as much as I love them, have a fatal flaw when it comes to transportation. Their ability to move through space is dependant on the distance of nearby celestial bodies. When the gravitational forces react with their fleets, it shunts them out quite a ways from their intended targets, and using traditional sublight propulsion, they can be years or even decades away from attacking their target if the system is large enough.
So, what you would see would be the creation of large integrated defense screens designed to detect Tyranids as well as destroy them through the use of orbital defense guns. As long as the fleet is not too massive, the odds of Tyranids reaching the ground are slim, and it would also make the use of large fleets relatively pointless unless a fleet manages to enter the imperium on a new axis where defenses are limited, and a rapid remobilization of firepower is required.
Also, phone autocorrect sucks.
If that's the case though, the Tyranids may well go with a Kraken style "spread out all the way across that front" approach, use hundreds of thousands of tiny fleets, slip straight past the cordon and ravage all the poorly defended worlds behind the line. Remember, you can't build a "wall" in space; the only reason something like the Cadian Gate works is because it's a relatively small region of space to police... and even then Chaos slips by in reasonable force on a regular basis.
If all the soft target agri-worlds and others start to fall, then after a couple of decades the supply lines to that shield wall collapse and all those trillions of Guardsmen begin to starve to death. There's also nothing to stop the fleets from focusing on all the non-Imperial worlds to begin with.
In this scenario, Tyranid victory is less likely to come from a hammer-blow fleet smashing key human bastions as it is from the Imperium having the galaxy quietly devoured when they aren't looking. It's a big galaxy and it doesn't matter if the first 50% of it to fall is not populated by humans.
Imagine the imperium as is. In a 1 on 1 grudge match, you would slowly see the imperium building up the outer perimeter or perhaps a distance within to create a defensive region of systems for safety. What most likely would occur is that Mars would eventually come up with a way to detect tyranid encroachment. Tyranids, as much as I love them, have a fatal flaw when it comes to transportation. Their ability to move through space is dependant on the distance of nearby celestial bodies. When the gravitational forces react with their fleets, it shunts them out quite a ways from their intended targets, and using traditional sublight propulsion, they can be years or even decades away from attacking their target if the system is large enough.
So, what you would see would be the creation of large integrated defense screens designed to detect Tyranids as well as destroy them through the use of orbital defense guns. As long as the fleet is not too massive, the odds of Tyranids reaching the ground are slim, and it would also make the use of large fleets relatively pointless unless a fleet manages to enter the imperium on a new axis where defenses are limited, and a rapid remobilization of firepower is required.
Also, phone autocorrect sucks.
If that's the case though, the Tyranids may well go with a Kraken style "spread out all the way across that front" approach, use hundreds of thousands of tiny fleets, slip straight past the cordon and ravage all the poorly defended worlds behind the line. Remember, you can't build a "wall" in space; the only reason something like the Cadian Gate works is because it's a relatively small region of space to police... and even then Chaos slips by in reasonable force on a regular basis.
If all the soft target agri-worlds and others start to fall, then after a couple of decades the supply lines to that shield wall collapse and all those trillions of Guardsmen begin to starve to death. There's also nothing to stop the fleets from focusing on all the non-Imperial worlds to begin with.
In this scenario, Tyranid victory is less likely to come from a hammer-blow fleet smashing key human bastions as it is from the Imperium having the galaxy quietly devoured when they aren't looking. It's a big galaxy and it doesn't matter if the first 50% of it to fall is not populated by humans.
It is part of the problem with space born empires. Realistically, a true wall is impossible with the issue of covering all axis, however, it is possible to turn systems and suitably dense areas into fortresses, the only issue is that while that would take considerable amounts of time, small density areas do raise the issue of allowing them to spread out and sneak through the lines. Ironically, you would have to rely on the massive amount of biomass contained within these hard points to persuade Tyrants to not go after weak targets.
The only way I see a clear cut victory for the imperium is if Mars found a way to create large scale gravity wells in space.
"There is a cancer eating at the Imperium. With each decade it advances deeper, leaving drained, dead worlds in its wake. This horror, this abomination, has thought and purpose that functions on an unimaginable, galactic scale and all we can do is try to stop the swarms of bioengineered monsters it unleashes upon us by instinct. We have given the horror a name to salve our fears; we call it the Tyranid race, but if is aware of us at all it must know us only as Prey."
Hive Fleet Grootslang 15000+
Servants of the Void 2000+
The IoM, without any other threats, would defeat the entire implied threat of the Tyranid race. Honestly, the full power and capability of the IoM is seriously under appreciated.
Heck, all Space Marines, focused against the Tyranids, would likely be able to halt them entirely.
The tyranids are stupid, wasteful and ultimately unfit to live. Even if the IoM can't stop them they will die in our galaxy. Something as silly as that couldn't have had any success against intelligent opponents.
Homebrew Imperial Guard: 1222nd Etrurian Lancers (Winged); Special Air-Assault Brigade (SAAB)
Homebrew Chaos: The Black Suns; A Medrengard Militia (think Iron Warriors-centric Blood Pact/Sons of Sek) 
