Thoughts on planetary combat

[Juubi Karakuchi]

I've given some thought to a somewhat controversial aspect of sci-fi warfare, that of planetary combat. Different sci-fi polities do it to differing degrees, but the main controversy is whether or not planetary combat is actually worth doing. Why go to the trouble, one may ask, when even a basic interstellar travel capability would allow for devastating bombardment from space, by redirecting asteriods if nothing else (yes, I have sat in the blue chair).
The simple answer is that one invades a planet because one wants the planet intact for some reason. You can trash it from orbit if you want, but the best you'll get is a pile of rubble (or a sea of molten lava in some cases). Capturing a planet intact allows the faction in question to capture at least some of the planet's infrastructure and resources intact, making it a boon to their war effort. They also present the enemy with a dilemma, since that the planet in question is not merely an industrial asset, but one of their own planets. Should they simply destroy it (should any nation use nukes on its own soil?), or must they expend blood and treasure trying to take it back? Thus, capturing an enemy planet can complicate said enemy's war strategy.

Now for the fun part, the actual mechanics of invading a planet. The first stage of conquering a planet is to gain control of the orbital space. The attacker must be able to position warships within this space to provide support, and to move transports in and out of it with a minimum of risk. The first resistance they are likely to face will be in orbital space, consisting of enemy warships and orbitals, which must be destroyed, driven away, or captured as appropriate.

Capturing a space station will be no simple matter, depending on its size, resilience, and purpose, with different varieties posing different problems. A space station built with real-life technology would be rather flimsy, and a battle going on inside would almost certainly result in its destruction. A large and fairly sturdy space station built by an experienced space-faring civilization, such as DS9, a Golan-2 (Star Wars) or a Ramillies (WH40k) would not face this particular problem. The problem instead would be actually capturing the station. To actually deploy troops onto the station, it would first be necessary to disable at least some of the station's weapons, creating a clear zone through which the transports could approach. One way around this is to make rapid deployments using small vessels that cannot be so easily intercepted. This was done in Halo 2, though it turned out that the Covenant's intent was to leave a bomb behind (which would have destroyed or seriously damaged the station had Master Chief not removed it). The fundamental weakness of this 'boarding torpedo' method is that it lacks staying power, since relatively few troops can be deployed by such means. Another way would be to combine the two, with the first wave creating a secure zone through which reinforcements can be deployed. Teleportation technology is a boon in this instance, since it means that this zone does not have to be around an airlock. The Klingons follow an aggressive approach in the famous DS9 episode 'Way of the Warrior', beaming into the station in small groups and spreading out to wreak havoc. This results in them being isolated and wiped out by the defenders, with reinforcements being cut off by virtue of the shields being restored. The Klingon fleet did not appear to have any dedicated transports, and deploying them to link up would have been suicidal anyway while the station's defences were still active. Assuming the attackers can overrun the station despite the various options available to the defenders (selectively deactivating life support, for example), then the Commander has the tricky decision of whether or not to self-destruct the station. Doing so would deny the attackers the station, but would shower the planet with wreckage (not a problem for Sisko, since DS9 was positioned some distance from Bajor). A better option might be to destroy any remaining systems, thus extending the time and investment needed for repairs.

With enemy starships and orbitals out of the way, the threat comes primarily from the ground (outside reinforcements aside). This comes in the form of ground-based weaponry and small starships (one of the few realistic applications for starfighters). The likely response depends on the extent and capability of the weapons. If the ground-based defences are sufficiently powerful to seriously threaten even the attacker's warships, then bombarding them would be ill-advised. If theatre or planetary shields enter the equation, such as in Star Wars, then bombardment would be completely ineffective, at least if Echo Base's shield is anything to go by. Only the most heavily-defended planets would enjoy complete coverage however, so the attacker will generally have the option of landing the troops elsewhere. This was the Imperium's approach in the Imperial Armour 'Siege of Vraks' trilogy, and also Vader's in 'The Empire Strikes Back'. It is at this point that planetary warfare begins in earnest. To have removed all orbital threats but still be faced with surface-based threats may be called orbital superiority, unless these threats can deny a significant proportion of the orbital space. Orbital supremacy would be to have removed the ground-based threats also, allowing starships to move through orbital space with complete impunity. In this respect, Vader's Death Squadron had orbital superiority at the Battle of Hoth, but the existence of an anti-starship Ion cannon protected by Echo Base's theatre shield denied them orbital supremacy. Captured orbitals, if in any workable condition, can be of help in this respect. The top end of a Space Elevator would be a particular boon, so long as the bottom end can be secured and the enemy can be prevented from destroying it. Warships can provide fire support and telemetry, while also ensuring that enemy starships do not interfere. In this situation, there is a good chance that the planet will simply surrender.

But even this stage has its complications. Unless the attacker's civilization is capable of mass-teleportation, then the transports must still get the necessary assets down to the surface, either by landing themselves or by sending down smaller vessels. They will be vulnerable in both cases to the defender's planetary assets, whether from air attacks or from surface-based weaponry. The Galactic Republic got around this in rather impressive fashion in 'Attack of the Clones', actually landing their Acclamator-I assault ships on the surface. They are described as withdrawing to orbit after delivery, suggesting that they could not move around inside an atmosphere much. Nonetheless, preventing them from landing would be no easy matter, since the kind of weaponry that could actually hurt them would be the weapons they have just evaded as described before. Any large concentrations of defending ground units could be destroyed by the Acclamator's own weaponry on the way down. The Imperium of Man makes use of various 'mass conveyances' and other transports, including Tetrarch heavy landers (Dan Abnett and Andy Hoare's Tactica Imperialis: A History of the Later Imperial Crusades). The possibilities with regard to landing lie on a spectrum, the extremes being a concentrated landing on a specific area or spreading over as wide an area as possible. If the attacker's choice of landing zones is limited, then a concentrated approach would be efficacious. If the attacker has safe access to a high percentage of the orbital space, then launching multiple attacks might be an option. If the defenders cannot oppose the landings in the early stages, when the attacking forces would have difficulty supporting one-another, then the defenders can be run ragged. However, this could lead to complications if enemy warships are abroad. A concentrated landing would be preferable in this case, since it limits the amount of orbital space the attacking warships must secure and defend. This refers to large-scale invasion landings, not small-scale raids, which could be carried out at the same time.

Once on the ground, the area under the attacking forces' control effectively becomes a 'state', which intends to conquer the rest of the planet. This 'state' is not merely a glorified spaceport, but also part of the attacker's infrastructure. Making good use of available resources allows the attacking forces to be less dependent on supplies brought in from space, while improving their ability to subsist if they are cut off. The war will from then on be little different from a conventional planetary war, apart from the role of starships. Both forces will use ground and air assets, and may even make use of (wet) naval assets if there are significant bodies of water. This presents a interesting complication for the attacker, since they must then either build, acquire, or import their naval vessels. Ground forces can further contribute to the struggle in orbit by destroying or capturing the defender's anti-starship weapons. The war will drag on until either one or the other is destroyed or surrenders, with the winner being the side able to maintain a constant flow of supplies and reinforcements. Even if they cannot achieve orbital superiority, let alone supremacy, being able to continue the planetary war can have an attrition effect on enemy morale, reaching the point where one side may find the cost unbearable and withdraw. In this case, the loser might bombard the planet anyway out of spite.

Overall, orbital superiority is not strictly necessary for a raid, or even for an initial landing. It is generally sufficient to have removed all enemy warships, since they can provide defending forces with telemetry and fire support in the same fashion as the attacker's warships. Ground-based anti-starship defences are nonetheless worthwhile, since they serve to limit the attacker's choice of landing zones. The attackers must destroy or capture these defences if they are to make maximum use of their starships. Once orbital supremacy is achieved, the defenders can be completely cut off from outside support, the attacker's warships being able to intercept any attempt to deliver reinforcements or supplies. Depending on the capabilities of the attacker's warships, blockade running is unlike to be off much help. The defenders, should they decide to fight on, must make use of what resources are available to them on the planet, or else bring them in by some other means (e.g. Stargates and analogues thereof). It is also worth mentioning the factor of planetary politics. If the planet is under a unified government, then this is no particular consideration. If the planet is controlled by a more federal or even confederal arrangement, then there is the added complication of disunity between local governing institutions and factions. A simple example would be real-life Earth, with different states disagreeing over how to respond to the appearance of an alien fleet. A canny attacker will attempt to exploit this where possible, persuading certain polities to surrender or simply not contribute to the defence, perhaps even to gain allies.

Different sci-fi universes handle planetary combat in different ways, while some either minimize its role or ignore it altogether. The most likely reason why some sci-fi polities choose not to engage in planetary combat is the difficulty of creating, transporting, and supplying the necessary planetary assets, along with the difficulties I have described. Real-life Earth, for example, has a population of over six billion. Its active military personnel number over ten million, out of over two billion suitable for military service. It currently possesses over one-hundred thousand land combat systems, a comparable number of air combat systems, over three-thousand naval vessels (numbers from globalfirepower.com), and over twenty-thousand miscellaneous nuclear devices. When a planet reaches a certain level of development, with a large population, a well-developed infrastructure, and advanced industrial capabilities, then it should be able to defend itself against all but the most massive invasions, assuming there is not a significant technological disparity. This happens in Harry Turtledove's World War series.

Under these circumstances, some sci-fi polities may decide that invading a developed planet is not practicable. Polities that regularly engage in planetary combat, notably the Galactic Empire and the Imperium of Man, have highly-developed space travel capabilities involving extremely large starships. The United Federation of Planets is a very different case, seeming to possess little in the way of planetary combat capability. This is not so strange when the relatively small size of its starships, the largest being the Sovereign class at 685 metres long, with an emergency passenger capacity of 6500, increasing to 9800 at a stretch (TNG novel, Losing the Peace, cited in Memory Beta). Under these conditions, for Starfleet to have to invade a planet like real-life Earth (as described above, but with ST technology) would be a nightmarish prospect. An Acclamator-I, by comparison, carries 16,000 clone troopers, along with their support personnel, 320 speeder bikes, 80 gunships, 48 AT-TE walkers, and 36 SPHA walkers (info from Wookiepedia). With ships like that around, its little wonder that so many planets in the SW universe invest in full-cover planetary shields.

[montypython]

One of my favorite sci-fi games on DOS was Star Legions, as it was a Star Trek style game dealing with planetary assaults from orbit, based on the Star Fleet series of games made by Trevor Sorenson and company. This one dealt with various stages of planetary assaults, from the point of securing orbit to knocking down planetary shields and dealing with planetary defensive fire and destruction of urban shield generators. I've generally used it as a template for what ST combined arms ground warfare would look like (aside from Star Fleet Battles and ST New Worlds).

[Samuel]

Capturing a planet intact allows the faction in question to capture at least some of the planet's infrastructure and resources intact, making it a boon to their war effort.

In a realistic scenario the majority of a solar system's industrial output would be in orbitals.

(should any nation use nukes on its own soil?)

Er, yes. As long as it isn't a ground burst.

Thus, capturing an enemy planet can complicate said enemy's war strategy.

Not really. It takes effort to capture an enemy world and as long as the effort is greater than the amount of resources that can be looted from the world there is no reason to liberate it.

A space station built with real-life technology would be rather flimsy, and a battle going on inside would almost certainly result in its destruction.

Why bother? Demand their surrender and blow apart the sections that refuse.

This comes in the form of ground-based weaponry and small starships (one of the few realistic applications for starfighters).

Why would fighters be useful? Why not just use ICBM equivalents?

If the ground-based defences are sufficiently powerful to seriously threaten even the attacker's warships, then bombarding them would be ill-advised. If theatre or planetary shields enter the equation, such as in Star Wars, then bombardment would be completely ineffective, at least if Echo Base's shield is anything to go by.

Planetary defenses will be stronger than ship based ones- planets can have as many shield generators as they want while ships are constrained by the fact that over a certain size they get ripped apart, heat disposal problems, etc. Of course this can be compensated by bringing a shitload of ships.

Only the most heavily-defended planets would enjoy complete coverage however, so the attacker will generally have the option of landing the troops elsewhere.

In any universe with FTL any planet worth taking will have planetary shields- the threat of a bombardment outside the shields is enough to bring any world to its knees. After all, shields don't help you if your enemy drops enough rounds that the atmosphere fills with dust and the temperature drops. Additionally shields help protect against rogue individuals and nuts- unless you are the sole group in charge of ships you want a way to insure no one slams into the planet at a significant fraction of c.

The war will from then on be little different from a conventional planetary war, apart from the role of starships.

Not really- any defender units in the field will be bombed to dust from space. It will be a series of siege operations unless the defender has made an underground system to try to link up targets. Than the attacker will try to find and bomb that.

When a planet reaches a certain level of development, with a large population, a well-developed infrastructure, and advanced industrial capabilities, then it should be able to defend itself against all but the most massive invasions, assuming there is not a significant technological disparity.

Attackers can simply siege the planet- slag the fields from orbit and give the defenders a choice about when they want to run out of food.

[Fingolfin_Noldor]

In a realistic scenario the majority of a solar system's industrial output would be in orbitals.

Space Stations are inherently expensive to maintain, along with the need to maintain large cargo ships to continuously supply raw materials. This is unlikely to be true.

[NetKnight]

Space Stations are inherently expensive to maintain, along with the need to maintain large cargo ships to continuously supply raw materials. This is unlikely to be true.

Samuel's "realistic scenario" seems to be one with civilizations that are closer to being Type 2 than Type 1. I agree with him that such civilizations seem more realistically in the business of having interstellar wars, although 'realism' of course depends entirely on the world-building rules of any particular universe.

Attackers can simply siege the planet- slag the fields from orbit and give the defenders a choice about when they want to run out of food.

Planets aren't Pacific atolls. They're either going to be self-sufficient in all but the most exotic of trade goods, or, if they are being fed and supplied from orbitals, virtually irrelevant. In the later scenario it is this extensive orbital infrastructure that presents the real threat to a belligerent power.




In any event, I wrote part of a long-winded argument, but I think the tl,dr defends itself well enough to post alone. If anyone takes issue with my argument, I'd have reason to elaborate more in responding, but it seems silly to subject anyone reading this to verbal diarrhea unless they're interested in reading it.

Leaving the setting being discussed completely undefined seems unwise: one can postulate any number of arbitrary systems of FTL that do not involve massively powerful starships: naturally occurring Stargate-like portals on planetary surfaces comes to mind immediately. The OP basically discusses Trek and Wars- style 'ships zooming around space' universes, so that's the tech base I'm using.

I'd argue that you 'average' non-genocidal interstellar war would be a very 'pure' Clausewitzian war of neutralizing enemy forces, and will consist of a series of Mahanian fleet actions in star systems with major orbital industry. Planets, siting at the bottom of their gravity well and with minuscule resources to work with compared to the entire system's, will generally be militarily irrelevant, and left to their own devices. The decision to invade a planet would be a political one, either because possession of the planet is a current war aim, or as a bargaining chip, provided the enemy is interested in the interests of the planet's population. Both aims require 'sentimental' interest in the planet and its population, not in its contribution to state military-industrial power, and an invasion for either reason is liable to be more trouble than it's worth.

If an invasion does take place, however, pinpoint orbital bombardment will be able to eliminate conspicuous SAM installations and airbases, massed enemy fighter squadrons and armies, and surface (at least) wet-naval units, so the planetary war will be one of comparatively small-unit actions, devolving to guerrilla and insurgent warfare. Iraq-in-space, in other words.

If the tech base doesn't support extensive orbital industry (ie, ~Type 1 civilizations), the war will still be a Mahanian affair, with battles likely above major planets, and with orbital bombardment of launch facilities neutralizing the planet's military value. In such a scenario, transporting a planetary invasion force is likely to be well-neigh impossible, as the OP notes.

[Ariphaos]

Space Stations are inherently expensive to maintain, along with the need to maintain large cargo ships to continuously supply raw materials. This is unlikely to be true.

I'm not sure what Samuel's fascination with orbitals is, but what do you mean by 'expensive'?

You could not possibly mean energetically expensive. You could not possibly mean materials expensive. You could not possibly mean labor intensive. What sort of magical definition for expensive are you talking about?

Ultimately, whoever controls the star wins. If you want to invade a planet, but the defender controls the output of their star, you are dead. If you control the output of the defending planet's star, you win.

[Lord of the Abyss]

In a realistic scenario the majority of a solar system's industrial output would be in orbitals.

Well, maybe, maybe not. In a setting with the previously mentioned planetary shields that are stronger than anything a ship or station has, wouldn't it make sense to concentrate as much of your industry as possible under its protection?

When a planet reaches a certain level of development, with a large population, a well-developed infrastructure, and advanced industrial capabilities, then it should be able to defend itself against all but the most massive invasions, assuming there is not a significant technological disparity.

Attackers can simply siege the planet- slag the fields from orbit and give the defenders a choice about when they want to run out of food.

That assumes that the attacker can actually feed them if they surrender. And that it is possible to punch through the planetary defenses that precisely, and not just kill off the planet.

And ( like your "just blow up the space station" idea ) it presumes a war of absolute ruthlessness; which is possible of course but not automatically the situation either in a sci-fi setting or real life. After all. we wouldn't be likely to nuke a city that refused surrender or burn off all the fields of a nation that refused. Why assume that all future civilizations will be worse than us? Or more suicidal, since that sort of behavior invites reprisals in kind, or escalation.

Ultimately, whoever controls the star wins. If you want to invade a planet, but the defender controls the output of their star, you are dead. If you control the output of the defending planet's star, you win.

Well, that assumes that the civilization DOES control the energy output of their stars.

[Formless]

If an invasion does take place, however, pinpoint orbital bombardment will be able to eliminate conspicuous SAM installations and airbases, massed enemy fighter squadrons and armies, and surface (at least) wet-naval units, so the planetary war will be one of comparatively small-unit actions, devolving to guerrilla and insurgent warfare. Iraq-in-space, in other words.

I have to ask, what kind of weapons are you assuming here? If your civilization uses lasers and similar directed energy weapons then orbital bombardment becomes a much more tricky affair. Any such weapon which can reach through the atmosphere from space to blast ground emplacements can just as easily reach from the ground to toast spacecraft. And the planet's crust gives planetary defenders essentially all the heat sink they need to outpace most realistically designed spacecraft. And that's before taking into consideration defenses mounted on oceangoing craft like submarines that don't have to sit in one place out in the open waiting to get blasted. With all those advantages, I wouldn't really consider the defenders helpless.

[TheLostVikings]

If an invasion does take place, however, pinpoint orbital bombardment will be able to eliminate conspicuous SAM installations and airbases, massed enemy fighter squadrons and armies, and surface (at least) wet-naval units, so the planetary war will be one of comparatively small-unit actions, devolving to guerrilla and insurgent warfare. Iraq-in-space, in other words.

I have to ask, what kind of weapons are you assuming here? If your civilization uses lasers and similar directed energy weapons then orbital bombardment becomes a much more tricky affair. Any such weapon which can reach through the atmosphere from space to blast ground emplacements can just as easily reach from the ground to toast spacecraft. And the planet's crust gives planetary defenders essentially all the heat sink they need to outpace most realistically designed spacecraft. And that's before taking into consideration defenses mounted on oceangoing craft like submarines that don't have to sit in one place out in the open waiting to get blasted. With all those advantages, I wouldn't really consider the defenders helpless.

Thanks to the lack of heat sinks in space compared to the ones on a planet the planet will always be able to field the more powerful force fields, however no earth sized planet sitting at the bottom of a huge gravity well will be able to toss Australia-sized rocks at thousands of km/h.

It's simple really, the space presence required to wage interstellar war means you have fucking powerful engines. Mount some of those engines at any random asteroid, or just push them up to speed with your generic space-"tugboat", and bam, there's your weapon of choice. The best part is that after being accelerated for a few AU they will still impart pretty much all their KE into the planet even if the defender completely vaporizes them.

But now you are probably thinking: "But we weren't talking about planet killers!" And neither was I. At the lower range you'd simply have something like the now canceled "Rods from God" project. Which is basically tossing solid tungsten rods the size of your average telephone-pole straight down at you. It packs the power of a Nuke without any fallout, and unlike a conventional ICBM there is no fragile warhead or electrics to disrupt, nor any explosive fuel to blow up. Just a large dense mass hurling down towards you at mach 10, which makes it relatively hard to knock of course. Put some steering fins and an unidirectional antenna at the rear end, and it could hit moving targets without the ground based defender being able to jam it.

Now for a ST/SW style universe this would obviously be laughably underpowered, but the solution is pretty simple: make them bigger. So if your universe has forcefields strong enough to stop an KE impactor the size of a Telephone-pole, then simply use one the size of an ICBM instead. And if that cant get past, go for one the size of the Empire state building. If they can block that, go for one the size of the Burj Dubai, then a 3 Km one, 5 Km one, 10 Km one, one the size of Manhattan, etc, etc. Stronger shields simply means you have to use an bigger rock to crack it. And once the forcefield gets pushed past it limit the rock that finally breaks trough will hopefully have decelerated enough that it wont crack the whole planet open. You might get a new mountain range, and some pretty spectacular Quakes as the crust settles down, but overall the majority of the planet will still be perfectly fine.

So if the defenders have a shield covering the entire planet you'd just have to pick the area you value the least, then start tossing rocks at it until the shield gives in. And if you are positing an universe without forcefield "shield" at all, well then you are probably fucked, because asteroids are a dime a dozen. And for any spacefaring civilization advanced enough to wage war in space, pushing some rocks up to speed would surely be a trivial matter.

[Marcus Aurelius]

And ( like your "just blow up the space station" idea ) it presumes a war of absolute ruthlessness; which is possible of course but not automatically the situation either in a sci-fi setting or real life. After all. we wouldn't be likely to nuke a city that refused surrender or burn off all the fields of a nation that refused. Why assume that all future civilizations will be worse than us? Or more suicidal, since that sort of behavior invites reprisals in kind, or escalation.

Exactly. There is no reason to assume that future civilizations, whether human or alien, will behave like the worst of Ancient civilizations on Earth. Of course some of them might still do so, but there are in fact good reasons to assume that it would not be the common way of doing things.

This brings me to one of my pet subjects: in Brin's Uplift Universe planetary combat occurs, because wide-scale orbital bombardment would in most cases be too ecologically damaging. Major ecological damage is a serious Galactic crime (and thus a very potential fast lane to extinction for the culprit species), so orbital actions are usually limited to surgical strikes and telemetry.

[Darth Wong]

It's simple really, the space presence required to wage interstellar war means you have fucking powerful engines.

Not necessarily. Hypothetically, if one discovered a low-energy "trick" to FTL (which is honestly no more unrealistic than a high-energy "trick" to FTL), then it might be possible to wage interstellar war with relatively "weak" (by sci-fi standards) power generation and engine technology. It would actually be amusing to subvert a few sci-fi cliches and create a sci-fi universe where most of the time and energy and danger of interstellar transit is in the sublight portions of the trip.

[Darth Wong]

Capturing a space station will be no simple matter, depending on its size, resilience, and purpose, with different varieties posing different problems. A space station built with real-life technology would be rather flimsy, and a battle going on inside would almost certainly result in its destruction. A large and fairly sturdy space station built by an experienced space-faring civilization, such as DS9, a Golan-2 (Star Wars) or a Ramillies (WH40k) would not face this particular problem. The problem instead would be actually capturing the station.

A sufficiently powerful space station would be easier to simply destroy, since it has little or no maneuvering power and so can't avoid things you fling at it. Any civilization capable of building such powerful military space stations is probably powerful enough to build a replacement almost as easily as rebuilding one which was violently captured and probably heavily damaged in the process, if not more so (especially if you consider the greatly reduced cost in manpower and equipment of avoiding the entire battle for the attacker).

To actually deploy troops onto the station, it would first be necessary to disable at least some of the station's weapons, creating a clear zone through which the transports could approach. One way around this is to make rapid deployments using small vessels that cannot be so easily intercepted.

If they can't shoot down small boarding vessels, they can't shoot down missiles or slugs. Far easier to simply hammer the station until it either surrenders or dies. Sending in men on small boarding vessels is wasteful of manpower.

With enemy starships and orbitals out of the way, the threat comes primarily from the ground (outside reinforcements aside). This comes in the form of ground-based weaponry and small starships (one of the few realistic applications for starfighters). The likely response depends on the extent and capability of the weapons. If the ground-based defences are sufficiently powerful to seriously threaten even the attacker's warships, then bombarding them would be ill-advised.

Not really; you can bombard them from really far away. The planet can't maneuver or hide behind something, while you can do both. The only way to deal with this is to have defense weapons that can destroy incoming projectiles and shields of some sort which can block incoming weapons. And the shields have to be ridiculously strong.

But even this stage has its complications. Unless the attacker's civilization is capable of mass-teleportation, then the transports must still get the necessary assets down to the surface, either by landing themselves or by sending down smaller vessels.

True. They need either very tough invasion vessels or a planet which has undergone heavy damage before they landed. The alternative is to force them to surrender with threats of more destruction, which is preferable to an invasion against armed resistance.

Once on the ground, the area under the attacking forces' control effectively becomes a 'state', which intends to conquer the rest of the planet.

This is another reason why it's preferable to extort a surrender out of the existing government.

Under these circumstances, some sci-fi polities may decide that invading a developed planet is not practicable. Polities that regularly engage in planetary combat, notably the Galactic Empire and the Imperium of Man, have highly-developed space travel capabilities involving extremely large starships. The United Federation of Planets is a very different case, seeming to possess little in the way of planetary combat capability. This is not so strange when the relatively small size of its starships, the largest being the Sovereign class at 685 metres long, with an emergency passenger capacity of 6500, increasing to 9800 at a stretch (TNG novel, Losing the Peace, cited in Memory Beta). Under these conditions, for Starfleet to have to invade a planet like real-life Earth (as described above, but with ST technology) would be a nightmarish prospect. An Acclamator-I, by comparison, carries 16,000 clone troopers, along with their support personnel, 320 speeder bikes, 80 gunships, 48 AT-TE walkers, and 36 SPHA walkers (info from Wookiepedia). With ships like that around, its little wonder that so many planets in the SW universe invest in full-cover planetary shields.

Even if you lack monster resources, it can still work with heavily demilitarized societies or planetary colonies where the settlement covers only small portion of the planet's surface (this also means there is plenty of room to land invasion forces with little or no opposition).

[NetKnight]

If an invasion does take place, however, pinpoint orbital bombardment will be able to eliminate conspicuous SAM installations and airbases, massed enemy fighter squadrons and armies, and surface (at least) wet-naval units, so the planetary war will be one of comparatively small-unit actions, devolving to guerrilla and insurgent warfare. Iraq-in-space, in other words.

I have to ask, what kind of weapons are you assuming here? If your civilization uses lasers and similar directed energy weapons then orbital bombardment becomes a much more tricky affair. Any such weapon which can reach through the atmosphere from space to blast ground emplacements can just as easily reach from the ground to toast spacecraft. And the planet's crust gives planetary defenders essentially all the heat sink they need to outpace most realistically designed spacecraft. And that's before taking into consideration defenses mounted on oceangoing craft like submarines that don't have to sit in one place out in the open waiting to get blasted. With all those advantages, I wouldn't really consider the defenders helpless.

TheLostVikings pretty well summed it up. Planetary energy weapon defenses do indeed have a massively superior heat sink- but they are also essentially stationary targets, sitting at the bottom of a large gravity well. An invading fleet can simply bombard them with missiles, kinetic-energy or warhead-bearing, from long range. In fact, they could probably hit the installations with their own energy weapons from long range, in both cases avoiding counter-fire with a small burn in a random direction.

Mobile energy weapons, if land-borne, will be small, slow, and easily dealt with by hitting the roads and rails they're transported on (off-road-vehicle mounted energy weapons would by necessity be far smaller than stationary or rail-and-road mounted weapons, and would still be slow from an orbital perspective). Sea-borne energy weapons can of course be larger than land-mobile weapons, but surface-ship platforms are even slower, and stick out like a sore thumb on the water. Submarines will likely have to surface to fire their energy weapons, making them targets.

Once long-range bombardment of Surface-to-Space defenses is concluded, your fleet can drop to a lower orbit for smaller pinpoint strikes against armies, etc. That is, if you're interested in invading at all. Major launch facilities aren't going anywhere either: they can be hit from long range just as well as Surface-to-Space defenses can.

Again, all of this depends on the tech base. Since planetary combat in an interstellar war is essentially dependent on FTL (planets are going to be utterly insignificant for a 'hard' interstellar civilization), the parameters of planetary combat are going to be based on some arbitrary set of world-building rules. Darth Wong noted another 'style' of FTL for which the above discussion does not apply. This is why I defined my setting as Trek-/Wars-type. Even so, I've really been neglecting Wars-type shields, although as TheLostVikings noted, the principles I've been discussing are germane to such settings.

Planetary defenses do add an interesting dimension to combat in 'verses without extensive space-based industry. Defending fleets can shelter under these 'shore batteries' in low orbit, while attackers can use their superior maneuverability and kinetic weapons performance, both by virtue of being higher in the gravity well, to bracket the enemy fleet with missile fire. In such a setting, planetary defenses are an actual direct military threat to the attacker, rather than a hindrance to negating the direct military threat of launch facilities. This doesn't apply as much to settings with extensive orbital industry: as I noted in my previous post, the real prize, and thus the focus of battle, in such systems is the space-based industry, and the direct military threat of planets is their launch capability.

[Ford Prefect]

But even this stage has its complications. Unless the attacker's civilization is capable of mass-teleportation, then the transports must still get the necessary assets down to the surface, either by landing themselves or by sending down smaller vessels.

True. They need either very tough invasion vessels or a planet which has undergone heavy damage before they landed. The alternative is to force them to surrender with threats of more destruction, which is preferable to an invasion against armed resistance.

It is also quite possible that the defensive forces cannot cover the entirety of the planet in question. 100% defence may be too expensive to build or maintain, and so surface defense could just be focussesed around areas of great importance (which might be entire countries). If there are 'weakpoints' in coverage then it might be possible to push an assault through. Pushing through an assault with numbers meaningful enough to actually take a whole planet is a little unlikely though, so it's probably not feasible.

[CaptainChewbacca]

It's simple really, the space presence required to wage interstellar war means you have fucking powerful engines.

Not necessarily. Hypothetically, if one discovered a low-energy "trick" to FTL (which is honestly no more unrealistic than a high-energy "trick" to FTL), then it might be possible to wage interstellar war with relatively "weak" (by sci-fi standards) power generation and engine technology. It would actually be amusing to subvert a few sci-fi cliches and create a sci-fi universe where most of the time and energy and danger of interstellar transit is in the sublight portions of the trip.

That reminds me of a short story that Turtledove wrote as a precursor to his Worldwar series. Turns out FTL is insanely easy to accomplish as well as antigravity, humans just never figured it out. So, modern-day earth gets invaded by technologically inferior aliens who have iron-hulled spaceships and repeating rifles.

[Serafina]

That reminds me of a short story that Turtledove wrote as a precursor to his Worldwar series. Turns out FTL is insanely easy to accomplish as well as antigravity, humans just never figured it out. So, modern-day earth gets invaded by technologically inferior aliens who have iron-hulled spaceships and repeating rifles.

Do you know the name of that story? I am looking forward to read it.

Kind regards
Fina

[Formless]

Thanks to the lack of heat sinks in space compared to the ones on a planet the planet will always be able to field the more powerful force fields, however no earth sized planet sitting at the bottom of a huge gravity well will be able to toss Australia-sized rocks at thousands of km/h.

Who fucking cares? If you want to destroy the biosphere you're in the wrong thread. That's like saying that the US can't lose a war because we can always just nuke the shit out of everyone. Oh wait, that opens the door to Russia nuking the shit out of us. Oh wait, there are resources in those countries we want to invade (oil, for example). Oh wait, we have in fact lost a war since getting the Bomb (Vietnam). The Herring is Red.

It's simple really, the space presence required to wage interstellar war means you have fucking powerful engines. Mount some of those engines at any random asteroid, or just push them up to speed with your generic space-"tugboat", and bam, there's your weapon of choice. The best part is that after being accelerated for a few AU they will still impart pretty much all their KE into the planet even if the defender completely vaporizes them.

The underlined statement is completely without merit or evidence. First of all, see Darth Wong's point; the setting's FTL mechanism ultimately decides how you explore the cosmos or wage war. Also, I dispute that you absolutely must have torchships in order to wage interplanetary war. In the age of sail a voyage by sea could take months, but that didn't stop people from waging war on the high seas. Further, as you increase the energy potential of the engines of spacecraft eventually you're going to make war as we know it impossible.

But that's not all! You also forget that unless you're setting has engines at the "war is obsolete" level it takes time to move an asteroid into striking position. In that time, what's to stop the planetary defenders from:

1. blowing holes in your attack fleet? They can still shoot at you, causing casualties in the process. This can mean the difference between successfully coercing the planetary government and a Pyrrhic victory.
2. calling in reinforcements? Its the classic way of breaking a siege. Consider especially the fact that if you can move asteroids everyone is going to be able to see it happen and there is no better way of showing hostility and genocidal intent in space.
3. (related to the above) returning the favor? You know the cliche`, the best defense is a good offense. Rome drew Hannibal away by attacking Carthage and stealing his thunder, so too can the planet's forces flip the tables on their attackers.

You also neglect other setting considerations. What do you do in a setting that does not have FTL? If you have a war between Earth and her colonies how likely do you think those colonies are to even consider such a genocidal tactic? And you don't even have to limit your thinking to Earth and solar system bound settings either, there are too few sci-fi with slowboats these days.

Your thinking is overly simplistic. Just because one side has weapons of astronomic destruction does NOT mean that every situation can be solved by successful deployment thereof.

But now you are probably thinking: "But we weren't talking about planet killers!" And neither was I.

Bullshit, that was exactly what you were talking about. "Australia sized rocks" =! the Rods of God, you stupid backpeddling shit.

At the lower range you'd simply have something like the now canceled "Rods from God" project. Which is basically tossing solid tungsten rods the size of your average telephone-pole straight down at you. It packs the power of a Nuke without any fallout, and unlike a conventional ICBM there is no fragile warhead or electrics to disrupt, nor any explosive fuel to blow up. Just a large dense mass hurling down towards you at mach 10, which makes it relatively hard to knock of course. Put some steering fins and an unidirectional antenna at the rear end, and it could hit moving targets without the ground based defender being able to jam it.

... so? What do you do when you can't find the weapons shooting at you because they're submerged underwater when they aren't firing? Not only does this protect them, but unlike in space there IS stealth on the surface of a planet. You seem to take perfect accuracy on the part of the orbital gunners for granted when this simply isn't the case. Also yet again not everything can be solved with judicious use of WMD's. What about weapons in civilian areas? And lastly, the planetary defenders aren't without powerful gun's either; nukes are destructive and powerful regardless of how fast they're moving.

And all that doesn't even matter because this argument is completely non-sequitor. Just because the orbital attackers have access to weapons the planetary defenders can't use is meaningless. The same is true of aircraft today, but that doesn't make them gods or something.

Now for a ST/SW style universe this would obviously be laughably underpowered,

Good thing I was never talking about Star Wars style sci-fi.

[Stark]

Isn't it pretty meaningless to try to come up with 'thoughts' on combat in a general 'scifi' sense when capabilities and balance are totally flexible between settings?

[Lord of the Abyss]

That reminds me of a short story that Turtledove wrote as a precursor to his Worldwar series. Turns out FTL is insanely easy to accomplish as well as antigravity, humans just never figured it out. So, modern-day earth gets invaded by technologically inferior aliens who have iron-hulled spaceships and repeating rifles.

Do you know the name of that story? I am looking forward to read it.

The Road Not Taken is the title.

[Formless]

TheLostVikings pretty well summed it up.

His "point" was that the attackers have access to weapons the defenders don't, and this magically gives them automatic victory while ignoring a whole slew of factors that should be taken into account when talking about siege warfare of any kind.

Planetary energy weapon defenses do indeed have a massively superior heat sink- but they are also essentially stationary targets, sitting at the bottom of a large gravity well.

Wrong. The planet itself might be stationary, but its a big planet with lots of places to hide in. See my idea of laser armed submarines.

An invading fleet can simply bombard them with missiles, kinetic-energy or warhead-bearing, from long range.

The longer the range, the harder it is to hit your target. Simply being able to hit the planet does NOT translate into being able to win the engagement, the same way that being able to hit the broad side of a barn does NOT mean you can hit the bandit taking cover next to the window of said barn (UNLESS you are willing to blow the whole damn thing up). And there is no range at which the orbital attackers can shoot that the planetary gunners can't match.

In fact, they could probably hit the installations with their own energy weapons from long range, in both cases avoiding counter-fire with a small burn in a random direction.

This only works as long as you have fuel. An issue the planetary defenders don't have to worry about.

Mobile energy weapons, if land-borne, will be small, slow, and easily dealt with by hitting the roads and rails they're transported on (off-road-vehicle mounted energy weapons would by necessity be far smaller than stationary or rail-and-road mounted weapons, and would still be slow from an orbital perspective).

Good thing I never suggested land based weapons. But even if I did, how would you deal with them if the tracks are underground?

Sea-borne energy weapons can of course be larger than land-mobile weapons, but surface-ship platforms are even slower, and stick out like a sore thumb on the water.

You forget the existence of weather. Unlike space, the surface of the earth is literally littered with things to hide under.

Submarines will likely have to surface to fire their energy weapons, making them targets.

True, but (and this is the reason I suggested them specifically) by only being targets when shooting or coming to port they limit the amount of times the orbital attackers can shoot at them. This advantage cannot be overstated.

Once long-range bombardment of Surface-to-Space defenses is concluded, your fleet can drop to a lower orbit for smaller pinpoint strikes against armies, etc. That is, if you're interested in invading at all. Major launch facilities aren't going anywhere either: they can be hit from long range just as well as Surface-to-Space defenses can.

As I already pointed out, there is no range you can shoot at that the planetary defenders can't match by the simple virtue that the weapons and targeting systems you are using work just as well from the ground as they do in space.

Again, all of this depends on the tech base. Since planetary combat in an interstellar war is essentially dependent on FTL (planets are going to be utterly insignificant for a 'hard' interstellar civilization), the parameters of planetary combat are going to be based on some arbitrary set of world-building rules. Darth Wong noted another 'style' of FTL for which the above discussion does not apply. This is why I defined my setting as Trek-/Wars-type. Even so, I've really been neglecting Wars-type shields, although as TheLostVikings noted, the principles I've been discussing are germane to such settings.

Then we're talking at cross purposes, since my interests are mainly in those harder settings.

[Simon_Jester]

It's simple really, the space presence required to wage interstellar war means you have fucking powerful engines.

Not necessarily. Hypothetically, if one discovered a low-energy "trick" to FTL (which is honestly no more unrealistic than a high-energy "trick" to FTL), then it might be possible to wage interstellar war with relatively "weak" (by sci-fi standards) power generation and engine technology. It would actually be amusing to subvert a few sci-fi cliches and create a sci-fi universe where most of the time and energy and danger of interstellar transit is in the sublight portions of the trip.

That has been done; Jerry Pournelle's CoDominium setting come to mind.

[Samuel]

Space Stations Cities are inherently expensive to maintain, along with the need to maintain large cargo ships trucks to continuously supply raw materials. This is unlikely to be true.

Sorry- couldn't resist. Why would building in space be more expensive once you get to the point that you are able to build entire interstellar fleets?

Planets aren't Pacific atolls. They're either going to be self-sufficient in all but the most exotic of trade goods, or, if they are being fed and supplied from orbitals, virtually irrelevant. In the later scenario it is this extensive orbital infrastructure that presents the real threat to a belligerent power.

I was actually refering to bombing the planets farmland and forcing them to surrender or potentially starve. Sure they would have a stockpile, but than you can start bombing the ships, trucks, trains and make their society completely unravel. Once you have the high ground they can't stop you.

Well, maybe, maybe not. In a setting with the previously mentioned planetary shields that are stronger than anything a ship or station has, wouldn't it make sense to concentrate as much of your industry as possible under its protection?

Than why not place it under an asteroid or a moon? Than you don't have to worry about destroying the biosphere with heat pollution and lower gravity reduces transportation costs.

That assumes that the attacker can actually feed them if they surrender.

Destroy enough so that they are forced to rely on granaries and let them know that if they don't surrender you will blow up said granaries.

And that it is possible to punch through the planetary defenses that precisely, and not just kill off the planet.

Well, if not you end up pouring heat into the planets atmosphere and making the climate go insane.

After all. we wouldn't be likely to nuke a city that refused surrender or burn off all the fields of a nation that refused.

And the alternatives are invasion and letting them live unsubdued, neither of which would be acceptable.

And the planet's crust gives planetary defenders essentially all the heat sink they need to outpace most realistically designed spacecraft. And that's before taking into consideration defenses mounted on oceangoing craft like submarines that don't have to sit in one place out in the open waiting to get blasted.

Where do you think the heat will be dumped?

blowing holes in your attack fleet? They can still shoot at you, causing casualties in the process. This can mean the difference between successfully coercing the planetary government and a Pyrrhic victory.

Several AUs is over 20 light minutes. Good luck hitting a target at that distance.

calling in reinforcements? Its the classic way of breaking a siege. Consider especially the fact that if you can move asteroids everyone is going to be able to see it happen and there is no better way of showing hostility and genocidal intent in space.

Yeah, but they can't bring in enough food or supplies to help the population if you start blasting. Threats of destruction is a good way to get a world to yield. If you have to do it to every world, there isn't really a point- just take out their space industry and leave a picket in orbit to prevent them from building up.

What do you do in a setting that does not have FTL?

Than there will be no planetary combat?

If you have a war between Earth and her colonies how likely do you think those colonies are to even consider such a genocidal tactic?

I doubt the colonies are going to have the population to invade Earth. Not to mention it is unlikely in hard sci-fi that by the time they can do a successful rebellion Earth has anything they need.

What about weapons in civilian areas?

I'm pretty sure that is a war crime.

And lastly, the planetary defenders aren't without powerful gun's either; nukes are destructive and powerful regardless of how fast they're moving.

And if you are far away they aren't a real threat any more than any other missile.

The same is true of aircraft today, but that doesn't make them gods or something.

Only because there is a limit to how high the planes can go. This does not apply to space ships.

The longer the range, the harder it is to hit your target.

How quickly does difficulty increase? Because if I can still hit you from a light hour away that isn't really a major problem.

Simply being able to hit the planet does NOT translate into being able to win the engagement, the same way that being able to hit the broad side of a barn does NOT mean you can hit the bandit taking cover next to the window of said barn (UNLESS you are willing to blow the whole damn thing up). And there is no range at which the orbital attackers can shoot that the planetary gunners can't match.

Sure there is. No matter where you are it takes the gunners longer to retaliate. If you attack from a light hour away it will be two hours before their attack can hit you. You know where they are and they can't move.

This only works as long as you have fuel. An issue the planetary defenders don't have to worry about.

If you are far enough away it doesn't take alot of fuel to provide enough random motion.

Good thing I never suggested land based weapons. But even if I did, how would you deal with them if the tracks are underground?

What would be the point? Why not simply have independent guns at the opening instead of wasting money on a giant rail system?

You forget the existence of weather. Unlike space, the surface of the earth is literally littered with things to hide under.

Can weather hide all the signs of your guns? I'm pretty sure that you can still see the heat through the clouds.

True, but (and this is the reason I suggested them specifically) by only being targets when shooting or coming to port they limit the amount of times the orbital attackers can shoot at them. This advantage cannot be overstated.

The real question is- how big can we make these monsters? If water provides enough protection they don't even need to hide- just duck to that depth better firing. Of course that leads to a situation where the attackers need to get close in order to have a short enough reaction time.

I don't think anyone has done a story on that theme. Any problems anyone can think of?

As I already pointed out, there is no range you can shoot at that the planetary defenders can't match by the simple virtue that the weapons and targeting systems you are using work just as well from the ground as they do in space.

Actually defenders have to deal with interference from the atmosphere.

[Darth Wong]

If you have a war between Earth and her colonies how likely do you think those colonies are to even consider such a genocidal tactic?

I doubt the colonies are going to have the population to invade Earth.

No, but Earth would have the population to invade colonies.

Simply being able to hit the planet does NOT translate into being able to win the engagement, the same way that being able to hit the broad side of a barn does NOT mean you can hit the bandit taking cover next to the window of said barn (UNLESS you are willing to blow the whole damn thing up). And there is no range at which the orbital attackers can shoot that the planetary gunners can't match.

Sure there is. No matter where you are it takes the gunners longer to retaliate. If you attack from a light hour away it will be two hours before their attack can hit you. You know where they are and they can't move.

Also, there is a much larger area effect from terrestrial targets, because atmosphere, ground, and water serve to transmit energy in all directions around the impact site. In space, there's radiation from a warhead burst and ... that's it. If it's a kinetic-kill vehicle and you miss, there's nothing at all.

[Lord of the Abyss]

Well, maybe, maybe not. In a setting with the previously mentioned planetary shields that are stronger than anything a ship or station has, wouldn't it make sense to concentrate as much of your industry as possible under its protection?

Than why not place it under an asteroid or a moon? Than you don't have to worry about destroying the biosphere with heat pollution and lower gravity reduces transportation costs.

But then an enemy can potentially cut you off from your supply. And if most of the population is on the planet, putting industry in space would increase not decrease costs; and that is the kind of population distribution that planetary shields could easily encourage. Why live in a relatively easily destroyed space station, when you can live behind a massively powerful shield?

That assumes that the attacker can actually feed them if they surrender.

Destroy enough so that they are forced to rely on granaries and let them know that if they don't surrender you will blow up said granaries.

And if the planet calls their bluff? If the goal is conquering the population, then killing off the population isn't an option. For that matter, they could threaten planetary suicide; use nukes/bioweapons/nanoweapons/whatever to render the planet useless if the enemy fleet actually does something genocidal like that. After all, at that point what do they have to lose?

And the planet's crust gives planetary defenders essentially all the heat sink they need to outpace most realistically designed spacecraft. And that's before taking into consideration defenses mounted on oceangoing craft like submarines that don't have to sit in one place out in the open waiting to get blasted.

Where do you think the heat will be dumped?

Oceans, glaciers, the air; all of those are far better heat sinks than space.

blowing holes in your attack fleet? They can still shoot at you, causing casualties in the process. This can mean the difference between successfully coercing the planetary government and a Pyrrhic victory.

Several AUs is over 20 light minutes. Good luck hitting a target at that distance.

Well; with a planet's resources you could be talking about millions of weapons. And if we are talking about energy weapons you can arrange the beam to spread quite a bit; you don't need to hit with enough concentrated power to burn a hole in the ship. You just need to overheat them.

calling in reinforcements? Its the classic way of breaking a siege. Consider especially the fact that if you can move asteroids everyone is going to be able to see it happen and there is no better way of showing hostility and genocidal intent in space.

Yeah, but they can't bring in enough food or supplies to help the population if you start blasting. Threats of destruction is a good way to get a world to yield.

It's also a way to get them to show up at your worlds and start making genocidal threats in turn. Or just killing your planets right off.

What about weapons in civilian areas?

I'm pretty sure that is a war crime.

So are all the mass destruction tactics you've been talking about.

Simply being able to hit the planet does NOT translate into being able to win the engagement, the same way that being able to hit the broad side of a barn does NOT mean you can hit the bandit taking cover next to the window of said barn (UNLESS you are willing to blow the whole damn thing up). And there is no range at which the orbital attackers can shoot that the planetary gunners can't match.

Sure there is. No matter where you are it takes the gunners longer to retaliate. If you attack from a light hour away it will be two hours before their attack can hit you. You know where they are and they can't move.

I think you have matters reversed. The planet will likely see the attacking fleet coming, while the ships won't know where the planetary weapons even are until their fire arrives. As is often pointed out, stealth is if not actually impossible a lot harder in space.

This only works as long as you have fuel. An issue the planetary defenders don't have to worry about.

If you are far enough away it doesn't take alot of fuel to provide enough random motion.

If they are firing millions of beams at a few ships at a time avoiding them might take more fuel than you seem to think. And if they are firing missiles, random motion isn't likely to do much at all. Another reason to build factories on planet; they can keep churning out weapons. If they are located underground, they'd be quite hard to find and identify from space.

You forget the existence of weather. Unlike space, the surface of the earth is literally littered with things to hide under.

Can weather hide all the signs of your guns? I'm pretty sure that you can still see the heat through the clouds.

On a planetary surface there's all sorts of heat sources.

As I already pointed out, there is no range you can shoot at that the planetary defenders can't match by the simple virtue that the weapons and targeting systems you are using work just as well from the ground as they do in space.

Actually defenders have to deal with interference from the atmosphere.

Generally. If they have the previously mentioned planetary or theater shields though, most versions of such things let outgoing fire pass just fine which would more than make up for it in terms of levelling the playing field. And of course they can just have more and stronger weapons to make up for it.

[Darth Wong]

Firing millions of weapons at a single ship multiple AUs away? Don't make me laugh; if that's necessary than you're bound to lose in an even-strength situation, because the enemy can spam enough ships to overwhelm your defenses. Not to mention the fact that he can simply use a planet or moon for cover.

If you're trying to defend a planet and you don't have crazy-powerful planetary shield technology like Star Wars, your best solution is an old solution: use constant patrols and scouts in order to identify and attack enemy ships before they can attack you. Drone swarms, for example. Trying to fight them off with weapons limited to the planet and its immediate area is madness.