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RedCommander wrote:
One thing to consider about planetary invasions is the following:

Let's say a planetary governor gets uppity. He refuses to pay his due taxes to the imperium, dubs himself as the sovereign ruler of his planet and declares that all imperial forces on his planets are to be killed on sight.

Do you know what is one of the most efficient ways for imperium to respond to this threat?

It is to do nothing. Yeah. That is, after reminding the governor that he and his planet stand now alone against a galaxy full of horrors. Should these horros decide to pay a visit to his planet... the imperium wouldn't send help. Because let's face it, if there's one thing the imperium does well even in the current age, it is to wage war.

The IoM doesn't really do that though. They may take some time to take care of it but letting a planet secede and doing nothing sets a bad precedent. Plus, it could take decades or even centuries for something like a xenos invasion or chaos assault. Other planets in the system, other systems in the sector, etc. etc. could see them and think "hey, me to." It could have a snowball affect and going from paying huge tithes to a distant world to none would be very appealing if there doesn't appear to be any negative repercussions. I mean, no one likes paying taxes. Besides, who to say the governor that got uppity isn't really a puppet of chaos or secretly throwing in with the Tau or part of a GSC? They'd have to respond.

Edited for grammer

 Ynneadwraith wrote:


Was probably a little blunt and flowery with my wording, making my points unclear. Sorry about that.

I don't actually think Marines (or special forces as a concept) are superfluous. In the specific instance of Marines being able to bring their orbital bombardment to bear, it would be superfluous to have the Marines there as well. If they're willing to bombard from orbit and wreck the infrastructure of the planet, they might as well do it with a far more numerous Navy vessel as Space Marines are a very limited resource in the Imperium.

Im not thinking you are understanding the point of the bombardments, at least as I have presented them. They aren't wholesale blowing up the hive and infrastructure, they are hitting key military locations which limit the resistance the Astartes themselves will face and they do it before the force has a chance to mobilize. If the enemy knows they are coming, then they would to a more blanket job with the Orbital Strikes, but the Astartes will still have to go in and hit whats left or confirm the the Governor is dead.

The phrase 'token resistance' was probably a bit disingenuous too. The full phrase should read 'moderately entrenched resistance', which means a planetary governor with reasonable military forces on his side who is smart enough to know what's coming for him, or a grass-roots anti-Imperium insurrection that by its nature isn't susceptible to having its leadership incapacitated.

The thing is its not necissarily about being smart enough to know whats coming for him, even for Governors in 40k there is a chance many of them haven't seen an Astartes and even fewer of them have insight into their operational capacities. Then there is also the fact that if a world is aware enough of Astartes, say because they will occasionally appear, do they know how often they appear? Is it a set schedule or do they show up at random? What they will be ready for is the Guard, so they will have static defenses, static defenses being easier for the more mobile Astartes forces to get around.

Lets say by some miracle of what ever faith the Governor now adheres to, he's aware of the Astartes and lets say he even has a Renegade Astartes advising him. And they've fully fortified, guns pointed to the sky, voidshields are live and they are waiting. Well the Loyalists will notice that when they show up, sure a more brazen Captain might order his Company full into action and then you'll very likely end up with a dead Company. Or, that Captain will take a look at whats going on and send a signal to the Chapter Fleet and perhaps the Sector Fleet. Then it wont be just 100 Astartes and the argument is moot.

but because I like the idea of Marines being the cavalry that the Guard call in when sh*t hits the fan. To be the cavalry, they need more than 100 men

Except in situations where the guard is already there and engaged they don't need to be more than 100 Men. If the enemy is already engaging with the Guard, those 100 Marines in the right places is all you need.

Some planet also have enough surface-to-air/space to deter an attack by SM.

 ILegion wrote:

RedCommander wrote:
One thing to consider about planetary invasions is the following:

Let's say a planetary governor gets uppity. He refuses to pay his due taxes to the imperium, dubs himself as the sovereign ruler of his planet and declares that all imperial forces on his planets are to be killed on sight.

Do you know what is one of the most efficient ways for imperium to respond to this threat?

It is to do nothing. Yeah. That is, after reminding the governor that he and his planet stand now alone against a galaxy full of horrors. Should these horros decide to pay a visit to his planet... the imperium wouldn't send help. Because let's face it, if there's one thing the imperium does well even in the current age, it is to wage war.

The IoM doesn't really do that though. They may take some time to take care of it but letting a planet secede and doing nothing sets a bad precedent. Plus, it could take decades or even centuries for something like a xenos invasion or chaos assault. Other planets in the system, other systems in the sector, etc. etc. could see them and think "hey, me to." It could have a snowball affect and going from paying huge tithes to a distant world to none would be very appealing if there doesn't appear to be any negative repercussions. I mean, no one likes paying taxes. Besides, who to say the governor that got uppity isn't really a puppet of chaos or secretly throwing in with the Tau or part of a GSC? They'd have to respond.

Edited for grammer

Yeah but if they are just regular uppity and not secretly in league with chaos or xenos, then the planet (that is, not necessarily the governor if you get my drift) probably comes to their senses and end their silly "Ooh, I think I know better than the Imperium!"-business. The sad thing is, the Imperium is the humankind's best bet.

If chaos and/or xenos are involved, then... it's on. Send in regiments of Imperial Guard and a detachment or a few of Space Marines to sort them out. Better keep an Exterminatus in hand too.

What about orbital defenses, many planets have orbital defense silos on the ground and even defensive satellites in orbit. One strike cruiser isn't going to be able to overcome that.


Automatically Appended Next Post:
I would even go so far as to say that the majority of imperial worlds that are Ciivilized class and above would have enough orbital defenses to contest a planetary landing, and certainly enough to keep a strike cruiser from establishing geostationary orbit and simply bombarding key installations with impunity

I am surprised nobody brought up the First Taros Interventation. A limited Space Marine strike force failed in their objective and was forced to withdraw with numerous casulties.

Edit: Deleted

The marines will also attack with a higher tempo. I remember reading somewhere that the Allies in Desert Storm attacked with a tempo much higher than the Allies in WW2 (2x as many combat actions per day, if I recall). Spacemarines will be higher still. Especially since they will be operating 24hrs a day.

The biggest problem with marines isn't that they aren't capable of performing a useful role in a planetary invasion, it's that their obscene cost is completely disproportionate to the limited value they add compared to the numberless conventional forces of the Imperium. If a marine company launches a drop pod assault into (surprise!) a proper air defense network and suffers 90% casualties before even touching the ground (with maybe a pod or two making it through by sheer luck) the Imperium has lost far more than they could possibly gain by winning the battle. And if you can only send the marines against weak targets with no air defense network, no sensors to detect an incoming threat in space, no defenses against enemy ships, no military forces capable of anti-marine tactics, etc, then what is the point in having them at all? A planet with nothing better than 1930s technology isn't going to last very long against a conventional IG force, and the guardsmen are a lot cheaper to produce and deploy.

 Peregrine wrote:
The biggest problem with marines isn't that they aren't capable of performing a useful role in a planetary invasion, it's that their obscene cost is completely disproportionate to the limited value they add compared to the numberless conventional forces of the Imperium. If a marine company launches a drop pod assault into (surprise!) a proper air defense network and suffers 90% casualties before even touching the ground (with maybe a pod or two making it through by sheer luck) the Imperium has lost far more than they could possibly gain by winning the battle. And if you can only send the marines against weak targets with no air defense network, no sensors to detect an incoming threat in space, no defenses against enemy ships, no military forces capable of anti-marine tactics, etc, then what is the point in having them at all? A planet with nothing better than 1930s technology isn't going to last very long against a conventional IG force, and the guardsmen are a lot cheaper to produce and deploy.

So, airborne troops are useless because you can't use them against heavy air defense? Tanks are useless because you can't send them against heavy anti-armour weaponry? Light infantry is useless because they'll suffer 90% casualties when you send them against machine gun emplacements? The US marines are useless because the US army can do the same job? Different kinds of troops fulfill different roles on a battlefield and for every type of troop and weapon in existence someone has found a weapon to counter it. That does not mean they are useless, it means that there are certain situations in which you want a certain weapon or type of troop.
Even the most stupid military commander would not order a drop pod assault into a defense network designed to counter it. Marines have ways to neutralise air defense networks before making an assault. Either they deploy outside of its reach and destroy it from the ground, or they simply destroy it from orbit.
When faced with a planet that has very heavy defenses, you ideally want to have both Marines and Guards. The Guard to make a frontal assault to distract the defenders, while the Marines concentrate all of their force on the weakest point in the defense and break through. You could have used Marines to do both tasks, but that would have been unnecessarily expensive. You could have used Guard to do both tasks, but Guardsmen would have had a much harder time breaking through the weak points in the enemy defense. You would have needed a very large force of Guardsmen to do so, which would have made distracting the enemy away from it virtually impossible.
A Space Marine Chapter can take a lightly or moderately defended planet without much issue, but it is not meant to invade and conquer a heavily defended planet all on its own. In the fluff, you see that such assaults are virtually always a combined effort of Marines and Guard.

Hidden AA defences mauled a Flesh Tearer company, so offering a seemingly easy and undefended target only to reveal your defences when the pods and thunderhawks are in range seems like a good plan.

 Bobthehero wrote:
Hidden AA defences mauled a Flesh Tearer company, so offering a seemingly easy and undefended target only to reveal your defences when the pods and thunderhawks are in range seems like a good plan.

Source?
Not to mention that the Flesh Tearers are already very headstrong and bloodthirsty.

Scion codex, 6th ed.

 Iron_Captain wrote:
So, airborne troops are useless because you can't use them against heavy air defense? Tanks are useless because you can't send them against heavy anti-armour weaponry? Light infantry is useless because they'll suffer 90% casualties when you send them against machine gun emplacements? The US marines are useless because the US army can do the same job? Different kinds of troops fulfill different roles on a battlefield and for every type of troop and weapon in existence someone has found a weapon to counter it. That does not mean they are useless, it means that there are certain situations in which you want a certain weapon or type of troop.

The difference is that real-world airborne troops are not orders of magnitude more expensive and irreplaceable than conventional forces. Remember, the Imperium has less than one space marine for every planet it owns. Even a single dead space marine is a horrifying loss for the Imperium, enough to make pretty much any gain a pyrrhic victory at best. For the comparison to real-world units to be accurate the US would have to be limited to a single airborne soldier, who costs $100 trillion to replace. Would this be a relevant military unit? Of course not.

Even the most stupid military commander would not order a drop pod assault into a defense network designed to counter it. Marines have ways to neutralise air defense networks before making an assault. Either they deploy outside of its reach and destroy it from the ground, or they simply destroy it from orbit.

Ok, so the marines deploy out of reach. Congratulations, now the enemy has time to react to them, and the marines get slaughtered. And good luck engaging a properly-defended planet from orbit when space marine warships are much weaker than a navy fleet. This whole argument seems to be based on the assumption that the marines will magically find a way to win and be relevant, and can't encounter situations where they simply have no chance of success.

When faced with a planet that has very heavy defenses, you ideally want to have both Marines and Guards. The Guard to make a frontal assault to distract the defenders, while the Marines concentrate all of their force on the weakest point in the defense and break through. You could have used Marines to do both tasks, but that would have been unnecessarily expensive. You could have used Guard to do both tasks, but Guardsmen would have had a much harder time breaking through the weak points in the enemy defense. You would have needed a very large force of Guardsmen to do so, which would have made distracting the enemy away from it virtually impossible.

Alternatively, this isn't WWI trench warfare, and this scenario ends up with a small force of marines isolated and surrounded by the enemy, and quickly killed. Breaking through a line of defenses doesn't magically win a war.

But 40k is WWI trench warfare... the Taus are the ones that don't are like that... and thats the reason they butchered Space Marines and Imperial Guard, because they used actual military strategies

 Peregrine wrote:
The biggest problem with marines isn't that they aren't capable of performing a useful role in a planetary invasion, it's that their obscene cost is completely disproportionate to the limited value they add compared to the numberless conventional forces of the Imperium. If a marine company launches a drop pod assault into (surprise!) a proper air defense network and suffers 90% casualties before even touching the ground (with maybe a pod or two making it through by sheer luck) the Imperium has lost far more than they could possibly gain by winning the battle. And if you can only send the marines against weak targets with no air defense network, no sensors to detect an incoming threat in space, no defenses against enemy ships, no military forces capable of anti-marine tactics, etc, then what is the point in having them at all? A planet with nothing better than 1930s technology isn't going to last very long against a conventional IG force, and the guardsmen are a lot cheaper to produce and deploy.

It's fairly well established that Drop Pods arrive too fast for any tracking systems to shoot them down other than blindly firing into the air and hoping you get lucky. Drop Pods are used when AA cover is too dense to insert normally.

Not always, in my example above, the pods get destroyed, alongside the rest.

 Grey Templar wrote:
It's fairly well established that Drop Pods arrive too fast for any tracking systems to shoot them down other than blindly firing into the air and hoping you get lucky. Drop Pods are used when AA cover is too dense to insert normally.

And that's just nonsense. We were able to get direct contact hits on incoming ICBMs way back in the 1970s (or earlier). There is no such thing as "too fast to hit", unless you're arbitrarily limiting the defender to hand-aimed WWII machine gun turrets. Against a proper Tau/Eldar/Necron air defense network, or even a high-end Imperial world, a drop pod assault would be suicide. Sure, the drop pods will work just fine against orks or a horde of PDF conscripts, but those are the easy targets that you don't need priceless super-soldiers to defeat.

Agreed from a realism perspective.

Teleported Terminators is what you're after if you want a suprise assault, not drop pods. They also have the benefit of being able to teleport behind defences. If you want a tactical insertion of small numbers to knock out leadership or some vital system, those are your dudes.

 Peregrine wrote:

 Iron_Captain wrote:
So, airborne troops are useless because you can't use them against heavy air defense? Tanks are useless because you can't send them against heavy anti-armour weaponry? Light infantry is useless because they'll suffer 90% casualties when you send them against machine gun emplacements? The US marines are useless because the US army can do the same job? Different kinds of troops fulfill different roles on a battlefield and for every type of troop and weapon in existence someone has found a weapon to counter it. That does not mean they are useless, it means that there are certain situations in which you want a certain weapon or type of troop.

The difference is that real-world airborne troops are not orders of magnitude more expensive and irreplaceable than conventional forces. Remember, the Imperium has less than one space marine for every planet it owns. Even a single dead space marine is a horrifying loss for the Imperium, enough to make pretty much any gain a pyrrhic victory at best. For the comparison to real-world units to be accurate the US would have to be limited to a single airborne soldier, who costs $100 trillion to replace. Would this be a relevant military unit? Of course not.

Airborne troops are highly trained specialists. They are quite a bit more expensive to maintain than a bunch of conscripts. More expensive in fact than Space Marines. Space Marines are not expensive at all to the Imperium. They are semi-independent, self-sustaining entities. The Imperium doesn't have to spend manpower or resources to keep them going, the Space Marines take care of that themselves.

 Peregrine wrote:

Even the most stupid military commander would not order a drop pod assault into a defense network designed to counter it. Marines have ways to neutralise air defense networks before making an assault. Either they deploy outside of its reach and destroy it from the ground, or they simply destroy it from orbit.

Ok, so the marines deploy out of reach. Congratulations, now the enemy has time to react to them, and the marines get slaughtered. And good luck engaging a properly-defended planet from orbit when space marine warships are much weaker than a navy fleet. This whole argument seems to be based on the assumption that the marines will magically find a way to win and be relevant, and can't encounter situations where they simply have no chance of success.

You assume the enemy is going to be faster than the Space Marines. Unless they are Eldar, that is not going to be the case. Mustering forces for a military operation is a very slow process that in reality often takes weeks or at least days. By the time the enemy force is prepared to move out and has reached the Space Marine drop site, the Marines will have moved on. This is one of the biggest advantages that Marines have over Guard forces. Marines are self-sustaining and can react and deploy virtually instantly, without the huge logistical operations that deploying an IG regiment requires.

 Peregrine wrote:

When faced with a planet that has very heavy defenses, you ideally want to have both Marines and Guards. The Guard to make a frontal assault to distract the defenders, while the Marines concentrate all of their force on the weakest point in the defense and break through. You could have used Marines to do both tasks, but that would have been unnecessarily expensive. You could have used Guard to do both tasks, but Guardsmen would have had a much harder time breaking through the weak points in the enemy defense. You would have needed a very large force of Guardsmen to do so, which would have made distracting the enemy away from it virtually impossible.

Alternatively, this isn't WWI trench warfare, and this scenario ends up with a small force of marines isolated and surrounded by the enemy, and quickly killed. Breaking through a line of defenses doesn't magically win a war.

Breaking through a defensive line does not magically win a war, but it can win the battle if the attacker exploits it properly. It does put the attacker in a very advantageous position to win the battle. The defender could surround the Marines, if it were not for the fact that they are already surrounded themselves, as the Guard is still assaulting the front line. Pulling away men from that defense to respond to the breach means that the defenders are going to be even more outnumbered and that that line is likely to be overrun. Not responding to the breach (because they can't spare the men or because the fact that in the chaos of battle they may simply not notice the breach in time) means they will soon be attacked in the back by the Marines or that the Marines will take out the whole command structure. Either way, a breach in your lines presents a nasty dilemma for you as defender.

 Iron_Captain wrote:
Airborne troops are highly trained specialists. They are quite a bit more expensive to maintain than a bunch of conscripts. More expensive in fact than Space Marines. Space Marines are not expensive at all to the Imperium. They are semi-independent, self-sustaining entities. The Imperium doesn't have to spend manpower or resources to keep them going, the Space Marines take care of that themselves.

Airborne troops do not cost orders of magnitude more to maintain. They're better trained than the average, but we don't spend trillions of dollars per soldier on them. And no, space marines are not free, just like you can't say that airborne troops are not expensive because the army is its own organization. If the Imperium disbanded the space marine chapters and put their resources to better use they would benefit significantly.

You assume the enemy is going to be faster than the Space Marines. Unless they are Eldar, that is not going to be the case. Mustering forces for a military operation is a very slow process that in reality often takes weeks or at least days. By the time the enemy force is prepared to move out and has reached the Space Marine drop site, the Marines will have moved on. This is one of the biggest advantages that Marines have over Guard forces. Marines are self-sustaining and can react and deploy virtually instantly, without the huge logistical operations that deploying an IG regiment requires.

Deploying outside the range of a proper air defense network, complete with high-altitude SAMs capable of engaging drop pods, anti-ship weapons that can threaten the ships carrying the marines, etc, means deploying hundreds or even thousands of miles away from the main target. And that's assuming the defenses are for a point target, not a complete planetary-scale network that leaves no room for a safe landing zone. And a planet that is doing the kind of things that draw an invasion attempt by the Imperium is going to be expecting a response. It might not be instant, but issuing krak missiles and lascannons to the defending troops is going to be a lot faster than marching thousands of miles across enemy territory to even get to the battlefield. And it doesn't matter how skilled a warrior you are, guided missiles with warheads that can punch a hole in a tank are going to kill you if you're anywhere in their effective range.

Also, all of this assumes an Imperial planet, where the defenses are entirely dependent on human crews. God help the marines if they're attacking a Tau planet, with swarms of drones, drone turrets, etc, that can be activated with the press of a button. It's quite likely that the few marines that survived to reach the surface would be slaughtered by automated defenses before reaching any living Tau.

Breaking through a defensive line does not magically win a war, but it can win the battle if the attacker exploits it properly. It does put the attacker in a very advantageous position to win the battle. The defender could surround the Marines, if it were not for the fact that they are already surrounded themselves, as the Guard is still assaulting the front line. Pulling away men from that defense to respond to the breach means that the defenders are going to be even more outnumbered and that that line is likely to be overrun. Not responding to the breach (because they can't spare the men or because the fact that in the chaos of battle they may simply not notice the breach in time) means they will soon be attacked in the back by the Marines or that the Marines will take out the whole command structure. Either way, a breach in your lines presents a nasty dilemma for you as defender.

Alternatively, this is not WWI trench warfare, and there is no single "front line". Why assume that dealing with the breach means pulling troops backward instead of, say, flattening the entire area with an air strike? Or disengaging from the fight and establishing a new defense line? Or sending reserves into the fight? Etc.

And why are you assuming that the marines will magically take out the command structure? Radios exist, after all, and the kind of low-end force that depends on having its entire command structure physically present on the front lines is the kind of easy target that you don't need marines to beat. More likely the command structure is in a bunker/command tank/etc hundreds of miles from the front lines, with only low-ranking officers (sergeants, platoon commanders, etc) in charge of small units located anywhere near the fighting. And taking out a sergeant isn't going to have any effect outside the immediate area and a small infantry unit that will shortly follow its leader into death.

Peregrine - are we assuming that standard 40k air defences are anywhere near our quality? They could be vastly inferior.

I headcanon that Space Marines use massive amounts of ECM when deepstriking to confuse targeting systems.

Actually I headcanon that it applies to pretty much all battlefields and only really expensive equipment can work in it which is why everybody seems to use line of sight instead of firing over the horizon etc.

 Peregrine wrote:

 Iron_Captain wrote:
Airborne troops are highly trained specialists. They are quite a bit more expensive to maintain than a bunch of conscripts. More expensive in fact than Space Marines. Space Marines are not expensive at all to the Imperium. They are semi-independent, self-sustaining entities. The Imperium doesn't have to spend manpower or resources to keep them going, the Space Marines take care of that themselves.

Airborne troops do not cost orders of magnitude more to maintain. They're better trained than the average, but we don't spend trillions of dollars per soldier on them. And no, space marines are not free, just like you can't say that airborne troops are not expensive because the army is its own organization. If the Imperium disbanded the space marine chapters and put their resources to better use they would benefit significantly.

The logic of your argument doesn't hold up regardless of the price difference. According to your logic, it should not matter if an army spends a thousand or ten thousand more on elite troops, why would they spend that extra money if they can get more cheaper soldiers instead to do the same job? The answer is that elite troops offer something that normal troops do not, and that that capability is worth paying for. If the Imperium ever needs to respond rapidly to a crisis, the Imperial Guard will be useless. It takes years to get through all the bureaucratic hassle and then a few years more to ready and transport the regiments. Meanwhile, a Space Marine Chapter offers the same strenght as multiple IG regiments, but they can be deployed at a moments notice. The Imperium needs them. If anything, the Imperium needs more Marines because there currently are so few they could not possibly cover the entire Imperium.
And no, the Imperium doesn't spend anything on the Marines after their founding. Marines have their own planet, their own resources and their own forges. If all Marine chapters were disbanded, the Imperium would face a huge civil war and at the end of it the only thing they'd get is a few relatively worthless planets. The Imperium already has over a million planets. It doesn't really need any more planets and it can easily afford to miss a few for the upkeep of a rapid reaction force.

 Peregrine wrote:

You assume the enemy is going to be faster than the Space Marines. Unless they are Eldar, that is not going to be the case. Mustering forces for a military operation is a very slow process that in reality often takes weeks or at least days. By the time the enemy force is prepared to move out and has reached the Space Marine drop site, the Marines will have moved on. This is one of the biggest advantages that Marines have over Guard forces. Marines are self-sustaining and can react and deploy virtually instantly, without the huge logistical operations that deploying an IG regiment requires.

Deploying outside the range of a proper air defense network, complete with high-altitude SAMs capable of engaging drop pods, anti-ship weapons that can threaten the ships carrying the marines, etc, means deploying hundreds or even thousands of miles away from the main target. And that's assuming the defenses are for a point target, not a complete planetary-scale network that leaves no room for a safe landing zone. And a planet that is doing the kind of things that draw an invasion attempt by the Imperium is going to be expecting a response. It might not be instant, but issuing krak missiles and lascannons to the defending troops is going to be a lot faster than marching thousands of miles across enemy territory to even get to the battlefield. And it doesn't matter how skilled a warrior you are, guided missiles with warheads that can punch a hole in a tank are going to kill you if you're anywhere in their effective range.
Also, all of this assumes an Imperial planet, where the defenses are entirely dependent on human crews. God help the marines if they're attacking a Tau planet, with swarms of drones, drone turrets, etc, that can be activated with the press of a button. It's quite likely that the few marines that survived to reach the surface would be slaughtered by automated defenses before reaching any living Tau.

Yeah, keep on moving those goalposts. No, Marines are not invincible. They can not overcome any defense imaginable. This is why very heavily defended worlds are never assaulted by just a single Marine company or a single Guard regiment. That would be suicide. Military commanders aren't stupid. For an attack on a well defended position to succeed, you need to greatly outnumber the defenders. In your scenario, if a planet is that well defended, there won't just be a single Marine company, there will be multiple and they will be backed up by a large army of Imperial Guard and a full Navy fleet.

 Peregrine wrote:

Breaking through a defensive line does not magically win a war, but it can win the battle if the attacker exploits it properly. It does put the attacker in a very advantageous position to win the battle. The defender could surround the Marines, if it were not for the fact that they are already surrounded themselves, as the Guard is still assaulting the front line. Pulling away men from that defense to respond to the breach means that the defenders are going to be even more outnumbered and that that line is likely to be overrun. Not responding to the breach (because they can't spare the men or because the fact that in the chaos of battle they may simply not notice the breach in time) means they will soon be attacked in the back by the Marines or that the Marines will take out the whole command structure. Either way, a breach in your lines presents a nasty dilemma for you as defender.

Alternatively, this is not WWI trench warfare, and there is no single "front line".

Don't move goalposts. I said "defensive line". That means there is a single front line. Any conventional war has a frontline, not just WWI style trench warfare.

 Peregrine wrote:
Why assume that dealing with the breach means pulling troops backward instead of, say, flattening the entire area with an air strike?

Because the attackers came from space. If you had an airforce, you could have prevented them from landing in the first place. To safely land forces on a planet you'd need air superiority. Therefore, since the attackers have already landed and started assaulting the defender's positions we can safely assume that the attackers have air superiority. Trying to bomb the area would be suicide on the part of the defender's pilots.

 Peregrine wrote:
Or disengaging from the fight and establishing a new defense line?

Probably the smartest move, but that means you'd have to retreat and lose the territory you were defending, meaning the attackers indeed won the battle.

 Peregrine wrote:
Or sending reserves into the fight? Etc.

Unless the attackers were stupid, they will outmatch you in sheer force and numbers (on a 3:1 ratio, if they followed basic strategic guidelines). If you send in reserves they will send in reserves too and nothing will change.

 Peregrine wrote:
And why are you assuming that the marines will magically take out the command structure? Radios exist, after all, and the kind of low-end force that depends on having its entire command structure physically present on the front lines is the kind of easy target that you don't need marines to beat. More likely the command structure is in a bunker/command tank/etc hundreds of miles from the front lines, with only low-ranking officers (sergeants, platoon commanders, etc) in charge of small units located anywhere near the fighting. And taking out a sergeant isn't going to have any effect outside the immediate area and a small infantry unit that will shortly follow its leader into death.

This is 40k. Commanders are always physically present on the front line. It wouldn't be heroic to sit in a bunker far away. Also, against Space Marines, sitting in a bunker far away from the frontlines is probably exactly what you do not want to be doing. What would stop the Marines from teleporting terminators in the middle of your bunker? You'd probably be safer on the frontlines, in the midst of your armies, moving around a lot.

Just put your command element in a bunker that's 6 feet tall, the Terminators are going to die when their heads materialize in the ceiling.

A 100 or a 1000 space marines are NOT going to pacify an entire planet no matter how superior they are to the locals.

Especially not if the planet's leadership knows that they are coming and has time to prepare for them.

If i am a rogue governor i am going to invest in snipers UEDs and boobytraps and attempt to not engage space marines in stand up battles.

Then i will prepare for a long assymetric war

Even if i lose a 1000 men for every one space marine the space marines would eventually lose by attrition.

godking wrote:
A 100 or a 1000 space marines are NOT going to pacify an entire planet no matter how superior they are to the locals.

Especially not if the planet's leadership knows that they are coming and has time to prepare for them.

If i am a rogue governor i am going to invest in snipers UEDs and boobytraps and attempt to not engage space marines in stand up battles.

Then i will prepare for a long assymetric war

Even if i lose a 1000 men for every one space marine the space marines would eventually lose by attrition.

No-one's saying they're pacifying and holding the planet.

Eliminating the leadership and infrastructure elements seems to work fine.

And again, if you are a rogue governor, odds are, you probably won't even expect Space Marines to come knocking, given how rare they are. Assymetric war won't help you - unless you can somehow gain void superiority, the Astartes can strike when and where they want, at your weakest elements.

They can't hold a planet, but they can break one into submission to a larger occupying and pacifying force.

 Peregrine wrote:

 Grey Templar wrote:
It's fairly well established that Drop Pods arrive too fast for any tracking systems to shoot them down other than blindly firing into the air and hoping you get lucky. Drop Pods are used when AA cover is too dense to insert normally.

And that's just nonsense. We were able to get direct contact hits on incoming ICBMs way back in the 1970s (or earlier). There is no such thing as "too fast to hit", unless you're arbitrarily limiting the defender to hand-aimed WWII machine gun turrets. Against a proper Tau/Eldar/Necron air defense network, or even a high-end Imperial world, a drop pod assault would be suicide. Sure, the drop pods will work just fine against orks or a horde of PDF conscripts, but those are the easy targets that you don't need priceless super-soldiers to defeat.

Hitting a missile is very different from hitting a drop pod. Drop Pods are much much faster than a missile. It's like trying to shoot down a meteor, which travel anywhere from 11-72 kilometers per second.

And again, pods were blown out of the sky by AA defences in the Scion codex, so they're not unhittable.

Bringing up terminators for a case study of a standard company assaulting a planet doesn't make much sense considering that each chapter only has about 100 suits of Terminator armor if they are lucky, and they are concentrated in the 1st company. So most companies will not have Terminator support fluff-wise.

Most planets have orbital defenses that will keep a strike cruiser from attaining a bombardment position, and also keep marines from deploying directly into a target area via drop pod or troop landers (thunderhawks). As mentioned before, fluff and in game stats prove that drop pods are vulnerable to AA fire.

If the marines deploy further out of range they could be hundreds or thousands of kilometers away from their intended target, and a long slog away from them. This means more time for the defended to entranced and prepare to repel whatever inevitable assault comes.

Honestly best case scenario would be for the strike cruiser to attempt to avoid detection and covertly insert its compliment of super soldiers. Then they can play bit more to their strengths, hitting targets suddenly and without warning before fading back into the countryside. Honestly I see a successful campaign for a marine company following stereotypical Alpha Legion or Raven Guard tactics. Establishing contacts with Loyalist locals or PDF would be important, and slowly growing an insurrection with the marines as the core would work I think.

Kinda like Gaunts Ghosts on Gereon, they insert and become the elite arm of a partisan force.