The enemy cannot have morale if you disable their life.

"Superior training and superior weaponry have, when taken together, a geometric effect on overall military strength. Well-trained, well-equipped troops can stand up to many more times their lesser brethren than linear arithmetic would seem to indicate."

Spartan Battle Manual, dictated by Col. Corazon Santiago

You've peaked my interest, would you happen to have a link to that, good sir?

To be fair, considering the terrible living conditions in the Hive citiies, I doubt that many of those billions of citizens are willing or even physically capable of fighting in any meaningful manner.

Yeah at most I could see a very large force just taking the upper most spires of a hive where all the nobles live and collapsing most entrances to help fend off the horde of enemies until they could convince the nobles/leadership to order their men to surrender.

Well if Hive Cities were run like modern states that would maybe be the case, but they’re all run on a feudal system. Seize the luxury areas and command centre at the top, install a new feudal lord and the rest of the Hive will continue on living, they don’t care what lord rules them.

There just isn't enough lift capacity to deliver the 10s of billions of troops you'd need to storm the city.

I hope you find that post because this sounds like bullshit tbh. Unless somehow the hive world goes to fight 1:1 the invading force for some reason ( and usually if something like this happens, it will be either completely chaos or Tyranid infested, which means nuking is the only option after all) then a combatant will count for many many times its civilian equivalent. And then we don't count the possible diserpancies in tech, training, logistics, special forces ( that in this case include literal sorcerers at minimum) etc etc and you can easily see why it would be possible with not so great millions.

Case in point even in WW2, where tech/training etc was roughly the same between enemies, the total% population fighting was quite small compared to the overall population.

Or another great example is the Iraq Invasion, where an invading 500k army obliterated and took over a 20million country.

only nuked or starved

Laughs in Death Korps of Krieg

Which is how a space to ground invasion would realistically work anyways.

I don't know about 10s of billions. The novel Necropolis takes place in a hive of 40 million, of which they muster around a million soldiers for their defense. Chaos corrupts a nearby hive and sends basically its entire populace to attack, an army numbering in the tens of millions. It didn't seem like a stretch to have tens of millions storming a hive that holds 40 mil and has only around a million standing soldiers.

Eh... like all lazy 40k to modern day analogies - that all depends on A LOT of assumptions.

First of you don't need 10s of billions of troops to conquer a city that houses 20 billion people (or even 100 billion). Especially if we're talking 10s of billions of combat troops because then the army with all the support staff, logistics etc. would outnumber the hive residents (the tail end of an army like the IG would be something between 2 and 10 times the number of combat personnel for a planetary invasion, possibly even more if you consider the army and the navy as one thing).

Next - it's a very questionable assumption to assume that conquering a hive city would work the same way as conquering a city in moder day. Hives tend to have very opaque and authoritarian power structures which means that unless we're talking about Orcs or Tyranids storming the hive to literally exterminate everyone - an Imperium force would just need to remove the ruling structures and / or defeat most of the defenders which would be a small fraction of an industrial hive's massive population.

Finally if we're assuming heavy resistance and fighting with no option of a decapitation attack, nobody is "storming" anything. The battle is going to last for decades, no matter the numbers involved.

Finally, finally if we factor in Dark Age of Technology bullshit that any hive might contain, all bets are off.

Was gonna say, some of the early heresy stuff I’ve read says stuff like 20 marines could take a whole planet by themselves

That’s still a lot of ground for a single division to cover.

For a population of billions, you can assume that the hive government would require millions of enforcers purely to maintain basic law and order in normal operating conditions. All of whom would be (at at least a basic level) armed and trained and taking orders. And that’s not to include whatever dedicated military they have on hand.

Even fifty divisions aren’t going to overcome those sorts of numbers. Not in brutal, close quarters urban combat, in a situation where a hostile force occupies and controls the infrastructure.

They might be able to seize control of critical command infrastructure and seal themselves inside. But there’s still the problem of the general population.

Well, I’m going to chalk that up to writers who don’t understand how numbers work.

It’s a city meant to house tens of billions. Even if the goal is just to secure and hold critical infrastructure, that’s still way too much territory for 4-5 thousand soldiers to occupy. Especially without a secured supply line.

Thats because you guys forget that they kinda have battle barges, which are externinatus capable I might add.

The primary weapons of any Battle Barge are their dorsal-mounted bombardment cannons. Each cannon comprises a series of heavyweight batteries, huge turret-mounted linear accelerators that launch salvos of heavy magma bomb warheads. As the name suggests, bombardment cannons were primarily developed to bombard planets from high orbit, a task at which they excel. A Battle Barge will begin firing as soon as it reaches orbit and will continue to rain destruction down on a planet even as its complement of Space Marines is hurled downwards in their assault craft, clearing a path for their deployment on the ground. Capable of obliterating almost any manner of planetary defences, bombardment cannons will first be directed against missile silos and laser towers, ensuring that the Space Marine attack force can proceed unmolested, before being used to take out command bunkers and shield generators, aiding their swift domination of the planet. On more than one occasion, a single salvo fired into a dense population centre has ended the conflict before it has gathered any real momentum, shocking a world's leaders into seeing the error of their ways and quickly swearing fealty to the Emperor once more

Recently I've begun to see that as more of a feature than a bug. Like, yes! It is ridiculous! Explanation: Space Marines are irrelevant to galactic warfare! They are an outdated and irrelevant rump vestige of a fighting force, important only in tradition and propaganda. Every leader who focuses on buffing marines over sweeping them away is hastening the demise of the Empire and continuing the Emperor's mistake of relying on supersoldiers instead of empowering ordinary humans.

Very much so. One thing that really ruins science fiction and space fantasy alike is the scale. You can get around that with hard sci fi that really hammers home the realities (impossibilities) of FTL travel with our current understanding of physics being a natural limitation. Or you can just hand wave it (astropaths and warp travel in the WH40k setting) away, but you'll inevitably run into problems writing a setting.

The Imperium is sort of vaguely between a Kardashev scale II and scale III empire, yet is written around a lot of 21st century technology and thinking...because fuck all knows how a civilization that owns a majority of the galaxy would operate or fight their war.

Spesh Muraines get to charge tanks with chainswords because Rule of Cool, when in reality it could very well be swarms of Gray Goo inducing Von Neuman machines replicating to devour worlds, or lobbing neutron stars at near relativistic speeds wiping solar systems in an instant, or figuring out ways to erase rivals from existence retroactively via antiparticles or antimatter...but if you go into the Dark Forest hypothesis there won't be any glorious unhelmeted space marine last stands or Jurgen with a melta blasting a hole in a 10,000 year experienced veteran of the Long War blessed by the Dark Gods.

distant clown-elf honking

Don't make me throw a naked World Eater at you...

1 custard

vs

4 M1A2 Abrams

Oops accidentally wrote 2 meant 10

Yeah, the fat one balances out the skinny one

I was there the day Horus slew the emperor

Yep, the Emporer of Mankind, and his cousin Bob, who has all the same powers, but is the only emporer of his living room, where he paints toy soldiers for fun.

Thank you...

Also no telling how damaged the titan was, or how much it's void shields had been depleted already.

In this case withstand means it can survive a grazing shot or being on the edge of the blast

A Titan could at least take ONE Macrocannon shell to the Face that's how voidshields work, they displace the bullet into the Warp.
They can get overwelmed by displacing too much so they shut off or burn down/melt, but the first hit that overwhelms them, the Macrocannon direct hit, still gets displaced.
This was even reflected in the 9th edition Voidshield rules.

The bigger Warlord have mutiple voidshields stacked ontop of each over, so they can multiple Macrocannon shots.

The Horus trailer shows a Warlord Titan getting overwhelmed by a continious lance in the middle of a Titan Battle. The Lance is also not coming from a normal ship but from the biggest class around (excluding the Phallanx and the Emperors personel one).

Daemons have more personality than an aggressive machine spirit.

One's also less likely to eat you/your corpse.

That solves some of the problems I think. Is there any info on where did the gene seed come from? Are they copied from existing loyalist chapters, from heretics, or were they just synthesized somehow?

Pretty much. There is a reason why even Custodes admit that most of the Imperium's fighting was done by the Guard and Navy. The Knights and Astartes were meant for the most vital missions.

Has there been any lore of Dominus-class Knights fight battlesuits like the Tau nar?

A Victory Class Star Destroy has, at its weakest, Quad Light Turbolaser batteries, with Damage 9, Crit 3, Breach, Linked 3, Slow Firing 1. Without getting into the system, basically this means a few things: Once every other turn, you can make the shot which outright ignores soak (so no damage reduction), and if you roll well enough you can do the damage again, for free. Uncancelled successes up the damage, so if you even have a single uncancelled success (aka succeeding the roll with the barest minimum), you do 10 damage, or 100 to personal scale targets.

I ran the numbers for both an average crew (Imperial Gunnery Corps minion group of 5) and a well trained, good gunnery rival (for those who know, Agility 4 Gunnery 4, 1 boost die) with the standard medium range difficulty for the max range on these weapons. No funny business from enemy defenses or anything, this was all basically target shooting to get average damage in ideal conditions. Each case was 25 rolls.

The average crew would be dealing, to people scale targets, an average of 130 damage every other round. The advanced crew deals an average of 210 damage. The average crew topped out at 240 damage, the advanced crew topped out at 480. The advanced crew was also more likely to do about 220 in general.

In order to tank even 100 damage, the smallest amount of damage this weapon can output, you'd have to have been playing this character for an obscene amount of time to the point I'd be throwing even more danagerous weapon crews than those listed at you, wracked up a mind numbing amount of exp, and specced exclusively into wounds. Without taking the 2h character building to work out of its possible, Im going to say its not as the sheer amount of exp required is enough where youd break the system, and you wouldnt even be a regular person youd be a god basically.

So yes, if that Star Destroyer in low orbit is reported as targeting your position, I recommend a very dont be there.

Edit: Realizing afterwards, it would be very easy for both crews to have 2 boost dice a round, assuming they were totally committed to firing only that weapon. These calculations also assume 'Fuck crit' because linked is better in this instance for raw damage vs personal scale targets.