So what do ground troops do?

[TheAtreides84]

Pretty much every form of FTL would allow you to destroy a planet. Relativistic weapons are simply that devastating. It would take only a single object massing a few tons at near lightspeed impacting earth to boil the surface.
If you want to keep stuff more intact on the planet, simply drop chemical and bioweapons into its atmosphere until the native species can't survive there any more. Bioweapons even allow you to be rather specific instead of causing a extinction event (which of course works too).
And lets be honest, in most cases you will not be able to use the biosphere anyway. Either its an unterraformed alien hellhole or the ones living there are even aliens. Either way, it is unlikely that you can even breath the atmosphere, digest its crops, etc. Why care keeping that alive instead of obliterating it all?

Well, perhaps to "vassalize", so to speak, the locals instead of wiping them out. It may very well be that genocide for conquest is a concept understandable only by the human race, while for advanced post-scarcity aliens destroying information wealth (i.e., wiping entire populations with their customs and traditions) is seen as absolute folly.

 

[Bullfrog]

So what do ground troops do?

board enemy ships.

 

[Rubidium]

For one thing, your entire post relies on the concept that detecting things in space is easy, it isn't. Heat doesn't travel as fast as light or sound, so using that as a means of detecting anything would be extremely foolhardy, by the time you picked up a heat signature the source would be long gone from that area. Furthermore, ships could be designed (like the normandy in Mass Effect) to prevent radiating heat on a detectable level. Detecting anything via EM or Visual is even *far* more difficult than that. This isn't a matter of technology, this is just a matter of physical law, sensors aren't magic. You throw in ECM and ECCM and things get even significantly harder for detection in space. Space isn't as empty as sci-fi makes it look. It is filled with background radiation and electro-magnetic fields, especially close to a planet or star. Gas Giants produce far more than regular planets. A ship would produce nothing close, and over distance any signatures would be lost in the background of everything else. It also takes time for those signatures to travel through space. Target acquisition would actually be one of the harder things in space, not easy.

Actually, heat in space will almost exclusively take the form of light (well electromagnetic radiation of some sort). There's no convection or conduction in a vacuum. And a difference of roughly 300 Kelvins between background and ship would be very visible to a decent detector. There really aren't especially practical ways to get around that. That becomes even more so when you take into account whatever propulsion system is being used (a rocket would leave a fairly large flare, while who knows what a warp engine would look like). Sure, you could hide behind a gas giant or something, but as you said, space is vast, and mostly not full of convenient gas giants to hide behind. Especially when you have to get to a certain planet. And this is where the vastness of space actually plays against our blockade-runners, because wherever they come from, they have to get to a known destination (whereas our blockade ships can be anywhere in the solar system), so intercepting becomes much easier.

Also, again you seem to severely underestimate the scale of space. While someone reliant on wormhole tech would be vulnerable to a blockade of the wormhole, someone with warp tech would not. Furthermore, if you are limiting your blockade to the wormhole, that leaves the planet to prepare weapons and ships to attack your blockade, or for reinforcements to come in and blast the ships at the gate. Also, if a planet is worth blockading, it is worth defending, which means any colony worth such effort will likely have planetary shields and anti-ship turrets dotted across the surface. To block out the sun requires very close proximity of a ship to actually pull off, or severe damage to the planet. The bigger the sun, or closer the planet, the harder the task at hand. This strategy suffers the same issue as a normal blockade - namely that the ship could be shot down. If the planet is an industrial world, it is far more likely to be able to throw considerable and near unending attacks on your fleet, far outlasting the effects of any blockade.

Blocking out the sun is a simple matter of putting up a sufficiently large solar sail at an arbitrary distance from the planet (realistically probably L1, just to keep the orbital mechanics simple). Yes, that's a big solar sail, but still probably cheaper than an invasion. Once it's up, the planet becomes the one that has to actively destroy it. And you can continue to toss missiles at the planet just as easily (since space is big). I agree that it's extremely expensive, but any invasion is almost certainly going to be even more expensive. It also commits you to stationing significant numbers of troops there as a garrison, and you'll still need some ships/defenses to prevent the original owners from taking it back from you.

Unlike any ship large enough to blockade or bombard the planet, troop ships can be significantly smaller, packed to the brim with troops and shields with minimal weapons. Their sole purpose is to get to the ground. Initial troops could disable defenses near a suitable landing site and more troops could begin landing. As more and more defenses are taken down, the orbital fleet has more options for assisting the ground invasion. Though sensitive area's are likely to be the most heavily defended and have the highest concentration of troops. Also, you can't make a planet "Surrender" any more than you can make Texas surrender. So long as there is a military garrison and intact bases and defenses, you'll have a problem regardless of what you do to the civilian population.

Any ship capable of carrying troops could be a missile just as easily (and at much less risk of loss of life on your side). And military garrisons surrender all the time when they are in hopeless situations (which is what having no sunlight, no fleet in space, and having an opponent capable of raining missiles down on you looks like to me).

Also, the reason you need to be close to a planet, is the farther out your blockade is, the more square miles you need to watch and the harder it would be to detect any ships. Space is 3 dimensional, so you need to blockade a spherical space that is *extremely* large.

Also, if you are trying to compare the damage of small arms fire and tanks/artillery to damage caused by any weapon powerful enough to penetrate the atmosphere and reach the surface from orbit (besides nuclear weapons), you're way off target there. Invasions would be focused on destroying a planets military garrisons and taking control of or destroying the planetary defenses. By that point, you've achieved control of the planet, though civilian resistance is dependent on the species/traits. Eventually, yes, you'd have the option to utilize bombardment, but that suffers the same diplomatic and long term ill effects discussed before. Also, blockading a planet, if you managed to pull it off, is a very long term ordeal and if enemy reinforcements arrive before the planet's garrison has surrendered, the planet can launch an attack on your forces in orbit to assist any incoming reinforcements. All colonies will initially be set up to be self sufficient because of the nature of space colonization, similar to how colonies in the america's quickly became self sufficient. It's the homeworld that benefits from the colonies, not the other way around. A colony that is worth attacking, as said, will be defended. Blockades will not be easy to pull off, there will be defenses against bombardment (and consquences), and there's only so many resources you can dedicate to an operation.

In the end, the quickest and most realistic option is for the fleet to distract the defenses while deploying troops, then to back off until troops begin taking down defenses. The fleet can slowly move back into low orbit and assist the invasion on varying levels until the garrison is defeated and the planetary defenses compromised fully. This is assuming you have any weapons that can even reach the surface from low orbit.

I should clarify my thinking for how a planet would be assaulted. Attacking fleet comes in, fights defending fleet and either destroys them or bottles them up near the planet. If you can't pull off at least local space superiority, you can't threaten the planet with ground troops or anything else. At that point you can start either shielding the planet from the sun and/or tossing large quantities of missiles at whatever targets you desire (working on the adage that a missile is more expendable than a ship full of soldiers, and if you hit them with enough, some will get through). It's basically the same as with your proposed ground invasion, except instead of ships carrying troops, they are missiles, which can be just as heavily shielded (especially since they don't have to keep fragile humans alive through the atmospheric entry).

If ground troops are used instead (as you seem to be proposing), there are two scenarios: a fully developed world, where you would presumably land in lightly defended areas and then try to advance overland towards the fortified areas, or an underdeveloped colony (where the atmosphere is probably either toxic or nonexistent, and the entire base is essentially a giant, air-tight space station that just happens to be located on a planet).

In the former case, the population of your target world is likely very spread out, requiring a major occupation force. Furthermore, if you are invading cross-species, the atmosphere is likely not friendly to your race, and the local food is at best inedible. So the invaders are at a fairly massive disadvantage, and will have to be constantly resupplied, whereas defenders can live off the land. Furthermore, any wound is likely fatal unless you can patch up the resultant leak, whereas guerrillas are likely to survive without problems. On the other hand, such a world is likely to be especially vulnerable to losing sunlight...

In the latter case, your invaders are almost certainly going to have to depressurize their landing area (since the defenders are unlikely to open the airlocks to let them in), and probably have to fight their way through numerous airtight bulkheads (once again exposing essentially wherever they end up fighting to the outer atmosphere/vacuum). The atmosphere will be hostile to your invaders either way, so your troops won't care, but the colony's population will suffer. And because such a colony is highly dependent on machinery to keep it alive (by doing things such as maintaining the atmosphere), an invasion that isn't very careful is likely to damage the vital areas during the fighting. That's going to be devastating to the colony, much more so than targeting the specific military installations with pinpoint missile strikes (which can be as damaging as you like, since you control the size of the missile and any warhead it contains, and the targets won't move).

I also question the level to which colonies will be self-sufficient; the American colonies didn't have to be terraformed, and were often at least initially heavily reliant on support/trade from native populations. Both of those would be problematic for a new colony; I'd expect them to be extremely precarious at least until terraforming was complete.

Either way, this discussion is rather pointless since PDX has made it clear they plan to use ground invasion forces (Fleet does the flying, ground troops do the dying).

Agreed on this count. It's a game, so whatever PDX feels makes the best gameplay will be what goes. I admit I also might be biased by my annoyance at maintaining and shepherding transport fleets around in MOO2 and similar games. I enjoy the discussion however, and hope you do as well.

 

[Zyrious]

Actually, heat in space will almost exclusively take the form of light (well electromagnetic radiation of some sort). There's no convection or conduction in a vacuum. And a difference of roughly 300 Kelvins between background and ship would be very visible to a decent detector. There really aren't especially practical ways to get around that. That becomes even more so when you take into account whatever propulsion system is being used (a rocket would leave a fairly large flare, while who knows what a warp engine would look like). Sure, you could hide behind a gas giant or something, but as you said, space is vast, and mostly not full of convenient gas giants to hide behind. Especially when you have to get to a certain planet. And this is where the vastness of space actually plays against our blockade-runners, because wherever they come from, they have to get to a known destination (whereas our blockade ships can be anywhere in the solar system), so intercepting becomes much easier.


Blocking out the sun is a simple matter of putting up a sufficiently large solar sail at an arbitrary distance from the planet (realistically probably L1, just to keep the orbital mechanics simple). Yes, that's a big solar sail, but still probably cheaper than an invasion. Once it's up, the planet becomes the one that has to actively destroy it. And you can continue to toss missiles at the planet just as easily (since space is big). I agree that it's extremely expensive, but any invasion is almost certainly going to be even more expensive. It also commits you to stationing significant numbers of troops there as a garrison, and you'll still need some ships/defenses to prevent the original owners from taking it back from you.



Any ship capable of carrying troops could be a missile just as easily (and at much less risk of loss of life on your side). And military garrisons surrender all the time when they are in hopeless situations (which is what having no sunlight, no fleet in space, and having an opponent capable of raining missiles down on you looks like to me).



I should clarify my thinking for how a planet would be assaulted. Attacking fleet comes in, fights defending fleet and either destroys them or bottles them up near the planet. If you can't pull off at least local space superiority, you can't threaten the planet with ground troops or anything else. At that point you can start either shielding the planet from the sun and/or tossing large quantities of missiles at whatever targets you desire (working on the adage that a missile is more expendable than a ship full of soldiers, and if you hit them with enough, some will get through). It's basically the same as with your proposed ground invasion, except instead of ships carrying troops, they are missiles, which can be just as heavily shielded (especially since they don't have to keep fragile humans alive through the atmospheric entry).

If ground troops are used instead (as you seem to be proposing), there are two scenarios: a fully developed world, where you would presumably land in lightly defended areas and then try to advance overland towards the fortified areas, or an underdeveloped colony (where the atmosphere is probably either toxic or nonexistent, and the entire base is essentially a giant, air-tight space station that just happens to be located on a planet).

In the former case, the population of your target world is likely very spread out, requiring a major occupation force. Furthermore, if you are invading cross-species, the atmosphere is likely not friendly to your race, and the local food is at best inedible. So the invaders are at a fairly massive disadvantage, and will have to be constantly resupplied, whereas defenders can live off the land. Furthermore, any wound is likely fatal unless you can patch up the resultant leak, whereas guerrillas are likely to survive without problems. On the other hand, such a world is likely to be especially vulnerable to losing sunlight...

In the latter case, your invaders are almost certainly going to have to depressurize their landing area (since the defenders are unlikely to open the airlocks to let them in), and probably have to fight their way through numerous airtight bulkheads (once again exposing essentially wherever they end up fighting to the outer atmosphere/vacuum). The atmosphere will be hostile to your invaders either way, so your troops won't care, but the colony's population will suffer. And because such a colony is highly dependent on machinery to keep it alive (by doing things such as maintaining the atmosphere), an invasion that isn't very careful is likely to damage the vital areas during the fighting. That's going to be devastating to the colony, much more so than targeting the specific military installations with pinpoint missile strikes (which can be as damaging as you like, since you control the size of the missile and any warhead it contains, and the targets won't move).

I also question the level to which colonies will be self-sufficient; the American colonies didn't have to be terraformed, and were often at least initially heavily reliant on support/trade from native populations. Both of those would be problematic for a new colony; I'd expect them to be extremely precarious at least until terraforming was complete.

Agreed on this count. It's a game, so whatever PDX feels makes the best gameplay will be what goes. I admit I also might be biased by my annoyance at maintaining and shepherding transport fleets around in MOO2 and similar games. I enjoy the discussion however, and hope you do as well.

The problem is that blockade runners will only be at sublight speeds for a short time. You're also assuming that your blockade fleet is faster than blockade runners, which in history has never been true. The vastness of space works in favor of the runners and smugglers and even escaping ships or fleets because they only need to be at sublight for a short period and it takes time for interceptors to close in, let alone open fire on, enemy vessels. Also, they can use the planets EM field and atmosphere for cover until entering warp/hyperspace/whatever. Again, the only race at severe disadvantage here is the "Stargate" race, and even they may have forms of extreme acceleration for short distances. Also, a planet could launch several devices that emit light and radiation to simulate a ships presence in order to screw up sensors (This would be part of the ECM and ECCM packages utilized by future militaries).

While it's true that missiles could penetrate a planetary shield, your assumption is that they could hit their targets. Troop ships won't be landing near the defense platforms which will likely have High-Energy Lasers which even the modern military uses to destroy missiles and which will be far more effective in the future. Their problem is range. Troop transports would be thicker and shielded and land out of range of laser defenses, and troops would proceed on foot and with tank/artillery support to take out or even outright capture enemy defenses.

Solar sails would be extremely vulnerable and, in most situations, atleast some enemy ships will remain present in tight orbit of the planet and a simple raid could destroy the extremely expensive solar sails. This also assumes Main Sequence dwarf stars, most stars in the galaxy are much larger(Atleast 5-10 solar masses larger, and there are plenty there are 20-100 fold larger), and most systems are binary (I know what you're thinking, if a sun is larger, the habital zone is further out, is it not? No, actually it depends on the type of star. Red Giants, which compose the majority of stars IIRC, actually have a closer habital zone, as opposed to further away). This could be a far more risky and expensive endeavor and the time it takes to set up may allow plenty of time for an enemy fleet to repair its ships and for reinforcements to arrive. Even if you do get it up, it is a long term form of siege and the enemy could raid it and destroy it fairly easily, even if they take losses or damage in the process.

Again, we can't have this scenario in a vacuum, we have to worry about enemy reinforcements, planetary defenses, planetary garrisons, and industrialized planets can build more ships and weapons to supplement current planetary defenses.

Also, when occupying a planet, you don't need to occupy every inch of it, not nowadays and especially not in the future. With ships easily capable of entering and exiting the atmosphere, once an enemy garrison is defeated and the main government facilities occupied, maintaining a few major military installations and a few troop ships in orbit will allow quick deployment of forces in any trouble area's on the planet and the population will know that. You'll still have the occasional uprising, but there's just no getting around that. At this point you'd also have the planet's defenses under your control, which should be the main goal of any invasion(Destroying their defenses and establishing your own, or capturing theirs), meaning the enemy can no longer quickly recapture the planet. Whereas if you simply blockade the planet, the enemy can break your blockade and have full control of the planet immediatly.

Now, what would be interesting here, is if you allowed both. You can have a blockade, with + - modifiers depending on how well the enemy is getting supplies in or out and whether or not the planet is self-sufficient. During this time, enemy reinforcements can at any time attack your blockade, which will have a - modifier to defense because the planetary defenses and any orbital ships will join the attack. So there is a cost/benefit difference between strategies. Blockades leave you vulnerable and tie up resources for a longer period of time, but are less costly and allow you to save troops/resources for more important targets. This could also affect invasion strategies. Mass bombardment and scorched earth means you have to rebuild the planets defenses, whereass normal ground invasion allows you to make use of the planet much more quickly. During the blockade, any orbiting fleets can attack you, and any planetary industry can build more ships and repair current ships in the fleet.

I do believe Total War has/had a system similar to that and it worked out fairly well. No matter what, you still need to garrison, less those on the planet regain control of the planetary defenses and fry the handful of ships you left behind. SW:Rebellion had a system similar to that, if you had an insufficient garrison and the planet's population did not support you, every so often you would lose more and more troops and once the planet rebelled, it would turn any defenses on the planet against you and become independent.

 

[Rubidium]

The problem is that blockade runners will only be at sublight speeds for a short time. You're also assuming that your blockade fleet is faster than blockade runners, which in history has never been true. The vastness of space works in favor of the runners and smugglers and even escaping ships or fleets because they only need to be at sublight for a short period and it takes time for interceptors to close in, let alone open fire on, enemy vessels. Also, they can use the planets EM field and atmosphere for cover until entering warp/hyperspace/whatever. Again, the only race at severe disadvantage here is the "Stargate" race, and even they may have forms of extreme acceleration for short distances. Also, a planet could launch several devices that emit light and radiation to simulate a ships presence in order to screw up sensors (This would be part of the ECM and ECCM packages utilized by future militaries).

This really depends on the specifics of how the FTL, communications and sensors work. Can a ship be detected in warp? Can it maneuver? Can it emerge near gravity wells? Don't forget that many of these might also affect the blockaders and missiles as well (e.g. FTL missiles make things very different). On the other hand, the historical tradeoffs for blockade runners would certainly apply; the need for speed means they will carry less cargo per ship, and they will probably be mostly civilians (and thus unlikely to press their luck too much; very few civilian ships are sufficiently fanatical to resist if an armed warship has a reasonable shot at destroying them and tells them to surrender). Add in that they will also probably have to be atmosphere capable (which will also complicate things), and they become significantly less effective. After all, you don't have to intercept all of them, just enough. Quite a few blockade runners slipped through the Union blockade during the American Civil War, but it was still sufficient to devastate the Confederate economy and cause a headache for their quartermasters.

While it's true that missiles could penetrate a planetary shield, your assumption is that they could hit their targets. Troop ships won't be landing near the defense platforms which will likely have High-Energy Lasers which even the modern military uses to destroy missiles and which will be far more effective in the future. Their problem is range. Troop transports would be thicker and shielded and land out of range of laser defenses, and troops would proceed on foot and with tank/artillery support to take out or even outright capture enemy defenses.

Saturate the target with missiles/bombs/small asteroids. Throw in decoys/MIRVs as needed. Expensive, perhaps, but still probably cheaper than a ground invasion (which would have to pry the enemy out of their emplaced defenses, and almost certainly have to do it without air superiority, as those same anti-missile defenses would pick off aircraft easily).

Solar sails would be extremely vulnerable and, in most situations, atleast some enemy ships will remain present in tight orbit of the planet and a simple raid could destroy the extremely expensive solar sails.

Sure, but they would also be very cheap to repair (just slap a patch on and you're done). If they are attacking it, then they are either launching missiles from the planet (probably the easiest, since a solar sail would have all the vulnerabilities a planet would have to lasers, but that's why you need to be launching missiles at the planet to knock out it's own defensive arsenal) or sortying (in which case their fleet has just left the protection of the planet, and is much more vulnerable to your own fleet; forcing that engagement is probably a victory in its own right).

This also assumes Main Sequence dwarf stars, most stars in the galaxy are much larger(Atleast 5-10 solar masses larger, and there are plenty there are 20-100 fold larger), and most systems are binary (I know what you're thinking, if a sun is larger, the habital zone is further out, is it not? No, actually it depends on the type of star. Red Giants, which compose the majority of stars IIRC, actually have a closer habital zone, as opposed to further away). This could be a far more risky and expensive endeavor and the time it takes to set up may allow plenty of time for an enemy fleet to repair its ships and for reinforcements to arrive. Even if you do get it up, it is a long term form of siege and the enemy could raid it and destroy it fairly easily, even if they take losses or damage in the process.

Sorry, but this bit is simply not true. Stars decrease rather rapidly in terms of size; the most common size is the red dwarf (a small fraction of a solar mass), and it decreases from there. The sun is actually in the top 20% or so of mass. This profile is both because of formation probabilities and lifespan (smaller stars live longer). I agree that the habitable zone is tricky to define (depending on the planet's atmosphere, mainly), but it's not that broad a range; the bigger the star the farther out the habitable zone is a pretty reasonable rule of thumb for the vast majority of stars. What makes it more tricky is things like bases on planets outside the habitable zone (e.g. if there are no planets inside the habitable zone, but for some strategic reason you want to occupy the system anyway), but these will probably be smaller.

Again, we can't have this scenario in a vacuum, we have to worry about enemy reinforcements, planetary defenses, planetary garrisons, and industrialized planets can build more ships and weapons to supplement current planetary defenses.

Also, when occupying a planet, you don't need to occupy every inch of it, not nowadays and especially not in the future. With ships easily capable of entering and exiting the atmosphere, once an enemy garrison is defeated and the main government facilities occupied, maintaining a few major military installations and a few troop ships in orbit will allow quick deployment of forces in any trouble area's on the planet and the population will know that. You'll still have the occasional uprising, but there's just no getting around that. At this point you'd also have the planet's defenses under your control, which should be the main goal of any invasion(Destroying their defenses and establishing your own, or capturing theirs), meaning the enemy can no longer quickly recapture the planet. Whereas if you simply blockade the planet, the enemy can break your blockade and have full control of the planet immediatly.

Certainly you have to worry about enemies breaking the siege. On the other hand, if they send a fleet sufficient to retake the space around the planet, your garrison is doomed anyway; there's no way it can deal with both subduing a hostile population and dealing with an enemy fleet with precision weaponry in orbit. They face the same problems the original defenders faced, except that the civilians will be uncooperative at best, and in open revolt at worst.

Now, what would be interesting here, is if you allowed both. You can have a blockade, with + - modifiers depending on how well the enemy is getting supplies in or out and whether or not the planet is self-sufficient. During this time, enemy reinforcements can at any time attack your blockade, which will have a - modifier to defense because the planetary defenses and any orbital ships will join the attack. So there is a cost/benefit difference between strategies. Blockades leave you vulnerable and tie up resources for a longer period of time, but are less costly and allow you to save troops/resources for more important targets. This could also affect invasion strategies. Mass bombardment and scorched earth means you have to rebuild the planets defenses, whereass normal ground invasion allows you to make use of the planet much more quickly. During the blockade, any orbiting fleets can attack you, and any planetary industry can build more ships and repair current ships in the fleet.

I do believe Total War has/had a system similar to that and it worked out fairly well. No matter what, you still need to garrison, less those on the planet regain control of the planetary defenses and fry the handful of ships you left behind. SW:Rebellion had a system similar to that, if you had an insufficient garrison and the planet's population did not support you, every so often you would lose more and more troops and once the planet rebelled, it would turn any defenses on the planet against you and become independent.

I agree the tradeoff could be interesting for gameplay. An obvious example, given the context, would be MOO2. Once the space battle is completed (and note that you could bombard the planet during the battle; indeed, in some cases you had to in order to destroy ground-based defenses), you had the option of invading or bombarding (and you could stop the bombardment at any time, but of course the bombs were fairly indiscriminate, and were as likely to destroy buildings/population as to knock out soldiers). Conquered population was generally resistant (and thus less productive and prone to revolt, potentially overwhelming your garrison if it wasn't big enough). You could also leave a few ships in orbit, and fight a battle whenever the system produced a new spaceship/planetary defense, with occasional bombardment as needed.

 

[Wyrm]

A futuristic society will most likely be very computer-centered and automated. So, you won't need millions or billions of troops to pacify a populace. You need to take control of computer hubs and infrastucture, government centers, intelligence headquarters, major mass-media-centers and such. An invasion will come in a few steps.

#1 - Orbital supremacy. This is vital to conducting any type of landing operations. You don't wanna launch dropships through a hail of fire from enemy battleships unless you use grasshoppers for troops or something.

#2 - Air supremacy. Take controll of the airspace of the planet. Knock out airfields/spaceports, defensive emplacements and such to make sure your dropships can move uncontested to any point of interest on the planet.

#3 - Bridge-heads. Find good spots to start disembarking troops and set up forward bases on the planet. This will make moving troops about faster and cheaper since you won't have to move from high-orbit. This is the phase where massive ground battles may take place and possibly the most interesting stage for game-play.

#4 - Start securing important infrastructure. Take control of civilian communication and services. Take over food and goods distribution. This stage will rely much more on small and highly mobile strike-groups, operating sort of like air-cavalry, moving in dropships and hitting fast and hard at very local areas but at almost any location.

#5 - Garrisoning and "reeducating" - after most of the planet's important infrastructure is secure, you will start the gruesome and dull task of garrisoning it and pacifying the population. This will be a combination of landing bulks of troops and recruiting police and security forces among the local population. Having control of the media and education systems will help to slowly make the planet more and more loyal to your cause. Ofcourse, this stage can be handled in myrriads of ways depending on ideologies and doctrines and would be separate from the invasion and be more like having occupation policies that can be set for a world under your control.



The faster you can move troops about uncontested, the fewer troops you will need for taking over a planet. Ofcourse, once techs that allow instantanous transportations such as Star Trek transporters comes into play, you will have horrible invasion scenarios where troops from both defender and attacker can be beamed directly into combat. Things will get ugly here...

 

[Zyrious]

This really depends on the specifics of how the FTL, communications and sensors work. Can a ship be detected in warp? Can it maneuver? Can it emerge near gravity wells? Don't forget that many of these might also affect the blockaders and missiles as well (e.g. FTL missiles make things very different). On the other hand, the historical tradeoffs for blockade runners would certainly apply; the need for speed means they will carry less cargo per ship, and they will probably be mostly civilians (and thus unlikely to press their luck too much; very few civilian ships are sufficiently fanatical to resist if an armed warship has a reasonable shot at destroying them and tells them to surrender). Add in that they will also probably have to be atmosphere capable (which will also complicate things), and they become significantly less effective. After all, you don't have to intercept all of them, just enough. Quite a few blockade runners slipped through the Union blockade during the American Civil War, but it was still sufficient to devastate the Confederate economy and cause a headache for their quartermasters.

Saturate the target with missiles/bombs/small asteroids. Throw in decoys/MIRVs as needed. Expensive, perhaps, but still probably cheaper than a ground invasion (which would have to pry the enemy out of their emplaced defenses, and almost certainly have to do it without air superiority, as those same anti-missile defenses would pick off aircraft easily).


Sure, but they would also be very cheap to repair (just slap a patch on and you're done). If they are attacking it, then they are either launching missiles from the planet (probably the easiest, since a solar sail would have all the vulnerabilities a planet would have to lasers, but that's why you need to be launching missiles at the planet to knock out it's own defensive arsenal) or sortying (in which case their fleet has just left the protection of the planet, and is much more vulnerable to your own fleet; forcing that engagement is probably a victory in its own right).


Sorry, but this bit is simply not true. Stars decrease rather rapidly in terms of size; the most common size is the red dwarf (a small fraction of a solar mass), and it decreases from there. The sun is actually in the top 20% or so of mass. This profile is both because of formation probabilities and lifespan (smaller stars live longer). I agree that the habitable zone is tricky to define (depending on the planet's atmosphere, mainly), but it's not that broad a range; the bigger the star the farther out the habitable zone is a pretty reasonable rule of thumb for the vast majority of stars. What makes it more tricky is things like bases on planets outside the habitable zone (e.g. if there are no planets inside the habitable zone, but for some strategic reason you want to occupy the system anyway), but these will probably be smaller.


Certainly you have to worry about enemies breaking the siege. On the other hand, if they send a fleet sufficient to retake the space around the planet, your garrison is doomed anyway; there's no way it can deal with both subduing a hostile population and dealing with an enemy fleet with precision weaponry in orbit. They face the same problems the original defenders faced, except that the civilians will be uncooperative at best, and in open revolt at worst.


I agree the tradeoff could be interesting for gameplay. An obvious example, given the context, would be MOO2. Once the space battle is completed (and note that you could bombard the planet during the battle; indeed, in some cases you had to in order to destroy ground-based defenses), you had the option of invading or bombarding (and you could stop the bombardment at any time, but of course the bombs were fairly indiscriminate, and were as likely to destroy buildings/population as to knock out soldiers). Conquered population was generally resistant (and thus less productive and prone to revolt, potentially overwhelming your garrison if it wasn't big enough). You could also leave a few ships in orbit, and fight a battle whenever the system produced a new spaceship/planetary defense, with occasional bombardment as needed.

In today's world the Military handles resupplying nations and regions cut off from supply, not civilian blockade runners. Were a planet blockaded, drones and fast military craft could deliver supply drops. Again, this is assuming a planet that even needs such supply drops. Also, as said previously, solar sails aren't cheap to make but they are cheap to destroy. The enemy could send in blockade runners, interceptors, and drones from other systems to destroy any solar sails, and the planet could also launch repeated attacks, included clusters of missiles and dummy missiles meant to fool the blockade, in addition to any future weaponry that may exist. This is assuming the sail isn't weak enough that the planet couldn't just put together a weak long range laser and continue to punch holes in it. Unless you plan on parking your entire blockade fleet in front of the sail. This is also assuming a planet cannot just use artificial means to maintain heat and keep plant-life alive for the duration of the blockade(or that the planet is at a point where it even makes a difference. An uninhabitable planet being used by the military as a military headquarters and production center isn't going to care if you block out the sun, and is just going to keep throwing everything they have at you until you leave or invade.

Also, remember a blockading fleet is going to be far out. This brings up another issue, how far out can planetary defenses go? There could be quite a lot of options that could turn a planet into a weapons platform and artillery station. Massive rail guns, extremely high powered particle weapons, or just high powered lasers, not to mention the multitude of weaker and precise lasers that would be easy to put all over the place by that point, preventing missiles from getting in. Getting anywhere near blockade range of a planet could be suicide for a fleet if it is properly defended. The only way to take a planet in that scenario is starship troopers style. Fly in guns blazing firing everything you have, decoys included, while massive troop transports deploy troops in the chaos, then your fleet pulls away while troops take out defenses, creating blindspots in space for your fleet to re-approach the planet.

Even if your fleet fired a huge plethora of missiles, they have to travel quite a bit to reach the planet and *then* re-enter the atmosphere, giving plenty of time for lasers to acquire and shoot down. Missiles will always be weak structurally, you can't put much on them or you limit fuel, eliminate their ability to survive re-entry, or sacrifice payload, or make them even easier to target. Small asteroids will just burn up in the atmosphere, asteroids big enough to not only survive re-entry, but actually cause significant damage, would be extremely difficult to move, and aim. Not only that, but it would take quite some time for them to actually reach the target, and you have to spend the time and resources to set up the equipment to properly move the asteroid. Then, the asteroids have to survive the planets defenses, and a large asteroid like that is going to get taken out no different than if you just flew a battleship at the planet, but the battleship would be smaller and have shields.

For every offensive weapon, there is a defensive counter. As jets began to take to the skies some people thought air superiority would remove the need for infantry or even ships. Instead billions of dollars developed many forms of anti-aircraft weaponry, and the military has stated several times that there will always be a need for ground infantry, both for invasion and for special operations. Really this discussion is simplifying warfare when it is far more complex, both militaries' will be utilizing hundreds of various technologies, including tech designed specifically to counter other tech, fool sensors, and beat blockades. Infact, blockades would be something especially planned for since it would be the obvious course of action. Anti-ship weapons, blockade runners and advanced drone supply ships, massive, heavily armed space stations both in deep space and in lower orbit.

A blockade is going to be heavily costly, because you are going to need to keep some of your strongest ships all around the planet or else the enemy fleet or ships on the surface could launch and destroy weaker blockading ships. This means your front line is weaker while you spend time blockading a world. Since you can't get too close to the planet, you have a huge coverage area you need to watch in order to intercept ships(which will be military craft). It will be expensive, time consuming, and may not even succeed. Boots on the ground gives guaranteed results as soon as the troops step out of a transport(which are thicker and well armored, as opposed to a missile), and planetary defenses can become *your weapons*, or at worst be taken out of the equation. If you lack the forces to occupy permanently at the moment, you can destroy enough of the defenses to make a blockade possible or gain the aid of orbital bombardment to turn the tide on the planet and break the spirit of its defenders.

Really though we could go back and forth with 2,000 different scenario's. There isn't going to be a "go to strategy" because militaries of the era will be sure to have counters ready. Ground Assaults will be necessary in one situation, blockades may work in another. Remember a planetary assault doesn't need to occupy the whole planet, but just military bases, communication centers, government centers and defense control. It's difficult to predict because we don't know how sensors will work, what the speed of ships will be, or even how many ships we will be able to afford to maintain. A blockade may be straight up impossible. I predict, as today, the military will utilize both options on a case by case basis, depending on the planets defenses, importance, the fleet resources available, the position of the enemy fleet, etc. etc. etc.

Not that i'm not enjoying this discussion, i just don't see it ever ending >.<