I've been tossing some thoughts around in my head about how a planetary assault might/should work. Wondering what thoughts others may have.
Ok, all of this is supposing that one force is looking to capture an entire planet, probably for on planet resources, and it is primarily a surprise attack.
Attackers - the phases that follow assume no significant resistance is encountered at any given phase. Under my defenders notes, I'll make some comments as to how the defenders can screw things up.
Phase 1: Assault ships and forces assemble at a staging area a jump away from the intended target. Using previously gathered intelligence, a battle plan is finalized.
Phase 2: "Probe" ships are sent to arrive in the target system a few hours before the fleet arrives. The responsibility of these small ships is to use passive sensors to identify, track and predict the courses of major military targets in the system, especially SDBs, orbital platforms, etc and have that information ready to transmit to the fleet as soon as it arrives. This step is optional, but can in many cases mean an overwhelmingly devestating surprise attack.
Phase 3: Fleet arrives, and receives the intelligence from the probe ships. Using that information, non-powered kinetic missiles are launched against major targets in the system, and the fleet begins moving towards it's target world. More kinetic missiles may be launched as the fleet proceeds, if more are identified, or additional targets become visible. Targets may be based upon the worlds surface, too.
Phase 4: Depending on distance, the kinetic missiles begin arriving at their target destinations. It is possible that the attack has been completely undetected until now, but not likely. Once the attackers are sure that their attack has been discovered, powered missiles are launched to finish off what the kinetic missiles have failed to destroy and against defenses that are too mobile/agile to target with kinetic ones.
Phase 5: Fleet reaches a high orbital position, from which they make a call for surrender. If necessary, a few more planet side locations are bombed with kinetic missiles, until surrender is given, or it becomes obvious they will have to begin a ground assault.
Phase 6: The ground assault. Transports and drop ships begin ferrying down assault troops and equipment to key areas to begin the ground assault, from here it becomes a "conventional" ground war.
Defenders:
Of course, ideally, the defenders will learn of the attack and the details prior to the fleet reaching it's staging area, so that the fleet can be ambushed while it is gathering. Reality is, even if the attack is discovered, the location of the staging area will probably not be known, or will not be known in time to do anything about it.
If the defenders are lucky enough to become aware of the attack prior to the arrival of the fleet, the probe ships are a key to defeating the invaders. Identify the probe ships when they arrive, and you can establish an area where the fleet should be arriving because they'll need to be in communications range to receive the targeting data as quickly as possible. Destroy the probe ships, and the fleet comes in "blind" for targeting data - if you want, you might even be able to feed them false data so they expend munitions targeting places that don't matter. Especially ironic would be targeting data that slingshots stuff around a moon and right back at them.
After that, the next way to discover the attack is coming is to detect the probe ships. For the most part, this could be difficult - even if you happen to detect that small scout ship jumping in system, just because it's sitting there doing apparently nothing doesn't mean it's a threat. If you're in a state of war, it's likely to be interpreted as such, but maybe not in a time of peace. So once it's detected and identified as a threat, you have to begin your response. If you're lucky, you'll have assets nearby that can take the probe ship out before the fleet arrives, if not, you'll need to start moving your forces into. Hopefully, you can begin transmitting the necessary orders in such a way that the probe ship doesn't know you've detected them.
Ok, so you're aware that the attack is coming, but there is nothing you can do about it except try and minimize damage. First thing is to establish movement orders/patterns for orbital assets that will take those items out of the trajectory of incoming kinetic missiles. There is a small window to make those in - you need to make them soon enough the missiles miss, but late enough that attackers haven't anticipated the movement and/or can't recalculate their shots. If possible, you begin evacuating targets - both orbital and planetside of all but essential personnel.
If possible, you begin manuevering as many of your forces as possible to intercept the attacking fleet well before it gets to orbit. This may be moving ships to intercept, or just missiles/mines.
If the attack catches you completely by surprise, you're a little more screwed. If your first notice of the impending attack is the arrival of the ships, and you view them as hostile, you immediately begin scrambling forces to intercept, launching missiles, and taking evacuation/evasive steps asap. If you're really not paying attention, and either don't spot the incoming ships, or simply don't treat them as hostile, then you will if you get lucky enough to spot the incoming kinetic missiles they launched. Miss those, and your first clue you're being attacked will be when the first missiles start hitting. If the attackers did their job well enough, your defenses will either be too far away to provide effective help, or will be expanding clouds of debris.
Once the attacker's reach high orbit, you have a tough choice to make. If they are there to simply wipe you out, you might as well surrender, because without orbital defenses, you're a sitting duck. All the attackers need to do is continually pepper you with kinetic and powered missiles until your cities and defenses are reduced to rubble - especially if they aren't concerned with killing off your civilians.
Now, if you have something they want, you've got a little more leeway. You have to be careful - push them too far, and they may just slag you from orbit. Your moment is when the drop shuttles begin their descent, particularly if your world has an atmsophere like Earth's, where there may be regions that cause communications black outs. If you can manage to take out enough of their assault forces, you can prolong the ground war - hopefully long enough until some sort of help arrives - because remember - if the attackers are in high orbit around your world, they're just as vulnerable to an outsystem attack as your orbital defenses were to them.
Thoughts as to how all of this applies to Traveller:
First and foremost, the first thing I notice is that there are no non-powered kinetic weapons like mass-drivers for Traveller starships in either the MgT or HG books. In some ways this makes sense - since these type of weapons will be most effective for planetary assault, it makes sense that civilian vessels would not be allowed to mount them by most any planetary, or stellar authority. OTOH, they should be available for military ships. If Mongoose doesn't step forward and work these into the rules, then someone else should come along and create some for MgT via the OGL.
Secondly, no matter what your thoughts are on j-drive IYTU, if you plan on having planetary assaults being a part of it the players , you should know how j-drive will affect things. If it's easy to detect incoming j-drive ships, then 'surprise' assaults will be harder/less effective. If it's hard to maintain fleet coherency during jump, again, thigns will be a little more difficult.
Third, certain types of system assets seem to make as much sense for defense as SDBs and fleets. FREX, deep buried planetary meson gun installations seem perfect for picking invading fleets from orbit. Their sensor equipment will be a little vulnerable, but make em redundant and mobile if you can, and they should be survivable. Likewise, "hidden" mass driver assets located elsewhere in the system could be effective at eliminating fleets once they do reach high orbit.
Other random thoughts:
It seems like planets without atmospheres will be in more danger from orbital bombardment than ones with. Likewise, deep oceans seem like a good place to hide planetary defense assets and evacuation sites.
I don't think you want to be on the receiving end of a planetary assault - all the odds seem to favor the invaders, unless a system is saturated with defense assets.
A good intelligence network is crucial, particularly if you are in a volitile region.
Ok, all of this is supposing that one force is looking to capture an entire planet, probably for on planet resources, and it is primarily a surprise attack.
Attackers - the phases that follow assume no significant resistance is encountered at any given phase. Under my defenders notes, I'll make some comments as to how the defenders can screw things up.
Phase 1: Assault ships and forces assemble at a staging area a jump away from the intended target. Using previously gathered intelligence, a battle plan is finalized.
Phase 2: "Probe" ships are sent to arrive in the target system a few hours before the fleet arrives. The responsibility of these small ships is to use passive sensors to identify, track and predict the courses of major military targets in the system, especially SDBs, orbital platforms, etc and have that information ready to transmit to the fleet as soon as it arrives. This step is optional, but can in many cases mean an overwhelmingly devestating surprise attack.
Phase 3: Fleet arrives, and receives the intelligence from the probe ships. Using that information, non-powered kinetic missiles are launched against major targets in the system, and the fleet begins moving towards it's target world. More kinetic missiles may be launched as the fleet proceeds, if more are identified, or additional targets become visible. Targets may be based upon the worlds surface, too.
Phase 4: Depending on distance, the kinetic missiles begin arriving at their target destinations. It is possible that the attack has been completely undetected until now, but not likely. Once the attackers are sure that their attack has been discovered, powered missiles are launched to finish off what the kinetic missiles have failed to destroy and against defenses that are too mobile/agile to target with kinetic ones.
Phase 5: Fleet reaches a high orbital position, from which they make a call for surrender. If necessary, a few more planet side locations are bombed with kinetic missiles, until surrender is given, or it becomes obvious they will have to begin a ground assault.
Phase 6: The ground assault. Transports and drop ships begin ferrying down assault troops and equipment to key areas to begin the ground assault, from here it becomes a "conventional" ground war.
Defenders:
Of course, ideally, the defenders will learn of the attack and the details prior to the fleet reaching it's staging area, so that the fleet can be ambushed while it is gathering. Reality is, even if the attack is discovered, the location of the staging area will probably not be known, or will not be known in time to do anything about it.
If the defenders are lucky enough to become aware of the attack prior to the arrival of the fleet, the probe ships are a key to defeating the invaders. Identify the probe ships when they arrive, and you can establish an area where the fleet should be arriving because they'll need to be in communications range to receive the targeting data as quickly as possible. Destroy the probe ships, and the fleet comes in "blind" for targeting data - if you want, you might even be able to feed them false data so they expend munitions targeting places that don't matter. Especially ironic would be targeting data that slingshots stuff around a moon and right back at them.
After that, the next way to discover the attack is coming is to detect the probe ships. For the most part, this could be difficult - even if you happen to detect that small scout ship jumping in system, just because it's sitting there doing apparently nothing doesn't mean it's a threat. If you're in a state of war, it's likely to be interpreted as such, but maybe not in a time of peace. So once it's detected and identified as a threat, you have to begin your response. If you're lucky, you'll have assets nearby that can take the probe ship out before the fleet arrives, if not, you'll need to start moving your forces into. Hopefully, you can begin transmitting the necessary orders in such a way that the probe ship doesn't know you've detected them.
Ok, so you're aware that the attack is coming, but there is nothing you can do about it except try and minimize damage. First thing is to establish movement orders/patterns for orbital assets that will take those items out of the trajectory of incoming kinetic missiles. There is a small window to make those in - you need to make them soon enough the missiles miss, but late enough that attackers haven't anticipated the movement and/or can't recalculate their shots. If possible, you begin evacuating targets - both orbital and planetside of all but essential personnel.
If possible, you begin manuevering as many of your forces as possible to intercept the attacking fleet well before it gets to orbit. This may be moving ships to intercept, or just missiles/mines.
If the attack catches you completely by surprise, you're a little more screwed. If your first notice of the impending attack is the arrival of the ships, and you view them as hostile, you immediately begin scrambling forces to intercept, launching missiles, and taking evacuation/evasive steps asap. If you're really not paying attention, and either don't spot the incoming ships, or simply don't treat them as hostile, then you will if you get lucky enough to spot the incoming kinetic missiles they launched. Miss those, and your first clue you're being attacked will be when the first missiles start hitting. If the attackers did their job well enough, your defenses will either be too far away to provide effective help, or will be expanding clouds of debris.
Once the attacker's reach high orbit, you have a tough choice to make. If they are there to simply wipe you out, you might as well surrender, because without orbital defenses, you're a sitting duck. All the attackers need to do is continually pepper you with kinetic and powered missiles until your cities and defenses are reduced to rubble - especially if they aren't concerned with killing off your civilians.
Now, if you have something they want, you've got a little more leeway. You have to be careful - push them too far, and they may just slag you from orbit. Your moment is when the drop shuttles begin their descent, particularly if your world has an atmsophere like Earth's, where there may be regions that cause communications black outs. If you can manage to take out enough of their assault forces, you can prolong the ground war - hopefully long enough until some sort of help arrives - because remember - if the attackers are in high orbit around your world, they're just as vulnerable to an outsystem attack as your orbital defenses were to them.
Thoughts as to how all of this applies to Traveller:
First and foremost, the first thing I notice is that there are no non-powered kinetic weapons like mass-drivers for Traveller starships in either the MgT or HG books. In some ways this makes sense - since these type of weapons will be most effective for planetary assault, it makes sense that civilian vessels would not be allowed to mount them by most any planetary, or stellar authority. OTOH, they should be available for military ships. If Mongoose doesn't step forward and work these into the rules, then someone else should come along and create some for MgT via the OGL.
Secondly, no matter what your thoughts are on j-drive IYTU, if you plan on having planetary assaults being a part of it the players , you should know how j-drive will affect things. If it's easy to detect incoming j-drive ships, then 'surprise' assaults will be harder/less effective. If it's hard to maintain fleet coherency during jump, again, thigns will be a little more difficult.
Third, certain types of system assets seem to make as much sense for defense as SDBs and fleets. FREX, deep buried planetary meson gun installations seem perfect for picking invading fleets from orbit. Their sensor equipment will be a little vulnerable, but make em redundant and mobile if you can, and they should be survivable. Likewise, "hidden" mass driver assets located elsewhere in the system could be effective at eliminating fleets once they do reach high orbit.
Other random thoughts:
It seems like planets without atmospheres will be in more danger from orbital bombardment than ones with. Likewise, deep oceans seem like a good place to hide planetary defense assets and evacuation sites.
I don't think you want to be on the receiving end of a planetary assault - all the odds seem to favor the invaders, unless a system is saturated with defense assets.
A good intelligence network is crucial, particularly if you are in a volitile region.
