What would you find in a planetary assault force?

[zizi666]

Lot of orbital bombing but what about planetary defense systems ?
If you can mount an enormous gun on a spaceship, it's got to be even easier to build some on the surface of a planet, and equally hard or easy to build some defense sattelites or stations orbiting your planet to defend it.
In the end, the most important factors will still be : difference in tech level and availability of resources and ofcourse economics.

my 2 cts.

[revford]

If the invasion is planned well in advance, you could have sleeper agents or commandos in place ready to take out key defence, power or transport stations to cause a bit of havoc and give your invading troops a better chance.

[frontal assault]

Much as I hate to raise the grim spectre of realism here, if the planet has a population in the billions (ie it's not a young colony or a mineral-extraction op or something) your fleet needs to have incredible/implausible amounts of life support and orbital interface capacity to even attempt an actual invasion with organic troops.  Raids are easy, and even landing a large force for a land grab isn't hard - planets are big places, and there will always be a backwater zone (probably continental in size) with no effective military defenses to oppose you.  Landing enough troops, equipment, and logistics infrastructure to overpower literally millions of enemies and take the whole world is much less believable.  You'd need to either scrub most of the defenders with mega-kill weapons from orbit (wrecking the planet's own infrastructure and civilian populace in the process) or bring about 3x as many troops as the defender to stand a chance of success.

A more plausible (but still somewhat silly) approach would be to raid the planet months or years in advance and seed the place with von Neumann machines programmed to hide and multiply themselves until your "real" invasion arrives, perhaps conducting limited offensives themselves if discovered or if their buildup goes unusually well.  You could then bring much, much smaller numbers of organic troops and their gear, with the bulk of the fighting done by the robots who are already on the ground - most of them having been built there by their ancestors.  Your starship troopers and orbital support fire would be used mostly to crack enemy strongpoints that the 'bots can't handle on their own, and to coordinate the robotic combat actions for better effect.  After conquest is achieved, you'd also want to shut down the combots and account for them all - no one in their right mind wants to risk rogue von Neumann killbots on the loose.

Of course, the defender can probably deploy the same type of self-replicating bots.  The political costs of doing so will probably restrain him from doing so till it's clear there's a threat, by which time he may be too late - geometric progressions are hard to play catch-up on.  Civilians won't be at all happy about living on a planet full of killer robots, especially after a few accidentall deaths.

Some interesting points here, though as I said last night, I'm still establishing the scale.  If I do go for a much larger scale, and certainly vast armies fighting each other makes for a more epic story, then I don't see why I can't have a fleet large enough to contain millions of troops.  Given that not all of a planet's populace would be involved in the fighting, it seems plausible that you might have troops going after specific objectives.  Additionally this would be towards the end of any battle given what's going on in space.  However I don't want robots, of any kind involved, simply because from the point of view of the story, it detracts from the human experience.

[dijit]

I think though no what what level of engagement, you're likely to be talking about a war that lasts for years before the last pockets of resistance are taken out. Think about D-Day and how long that took. Then there's the obvious problem with future war stuff - weapons of mass destruction - Secured the space port, well unfortunately that was mined with a huge atomic warhead - bang went your advantage.

[frontal assault]

I think though no what what level of engagement, you're likely to be talking about a war that lasts for years before the last pockets of resistance are taken out. Think about D-Day and how long that took. Then there's the obvious problem with future war stuff - weapons of mass destruction - Secured the space port, well unfortunately that was mined with a huge atomic warhead - bang went your advantage.

This is pretty much while I'm still in the 'working things out' stage of planning.  I remember when I first saw the re-imagined Battlestar Galactica, complete with Baseships nuking Caprica and I thought that's how you assault a planet.  Unfortunately nukes don't allow for some of the more sublime parts of the human drama where combat is concerned, namely the emotions you get from those engaged in close-quarters fighting.  I want that in the novel, so the nuke element is going to have be a little muted.  Of course from a realistic point of view, if you've got loads of nukes while attacking a planet, you're going to use them.

[revford]

If you want an alternative to raining nukes from the sky, you could do the collect asteroids and drive them towards the planet trick.

Rocks fall from the sky, with infantry landers following them in.

[frontal assault]

If you want an alternative to raining nukes from the sky, you could do the collect asteroids and drive them towards the planet trick.

Rocks fall from the sky, with infantry landers following them in.

As tempting an idea at this is, what about all the fire and dust the impacts would throw into the atmosphere?  It would fighting extremely difficult if not utterly impossible.

[dijit]

If you want an alternative to raining nukes from the sky, you could do the collect asteroids and drive them towards the planet trick.

Rocks fall from the sky, with infantry landers following them in.

That depends largely on whether you're trying to take the planet more or less intact or just destroy the enemy forces (ie the planet doesn't matter all that much). I see nukes/asteroids being mainly used as last ditch strategies by the defenders (ie taking out that vital captured space port) or by the offensive for neutralising large areas of threat.

[jp762]

Neutron bombs.
Microwave the ba%$#rdŁ and then take over.
After that it wouldnt take much.
They exist today so why not in the future?
http://www.nuclearfiles.org/menu/key-issues/nuclear-weapons/basics/neutron-bomb.htm

[ErikB]

To make any sort of accurate response we'd need to know more about the planet you're planning to invade. 

Basic steps:

1) Recce from space  (ideally hidden/stealthy), listen to transmissions, photograph, like a submarine in the real world

2) Recce from atmosphere (ideally hidden/stealthy), taking closer photos, monitoring more transmissions (like radar frequencies), checking out the atmosphere, temepratures, etc.

3) Sneak in recce troops (boots on the ground), like UDT, Force Recon, Spec Forces, Rangers, LURP-Ds, and so on, living on the surface and getting a sense of the operating environment (biosphere, animals, natives, etc.)

4) Strike from space to destroy anti-space weapons and any anti-air weapons they can (like a T-LAM strike) so that the orbiting force is not in danger.  Recall the bugs shooting down the starships in the starship troopers movies.  Want to avoid that happening.

5) Strike from the atmosphere to destroy anti-air defenses and whatever threats could lurk in the landing zones.  Hit a variety of areas to keep them guessing where you actually plan to land.  Could also sew minefields (could be burrowing robots or diseases with a limited lifetime, whatever).

6) Land first troops and supplies (think opening sequence of Private Ryan, before they got the tanks on the beach).  Could be troops dropped via drop tubes first, with lots of chaff and explosives landing, too.  Their job is to knock out whatever defenses are remaining which could be a lot if defending troops are being mobilized after the first strikes.

7) Land second wave of troops, mostly support, everything from armor and artillery to food, field hospitals, airfields, repair stations, ELINT services, and some larger command and control.  Make the landing area (beach head) nice and secure for supplies to land safely.  Now you have a little island cut out and you can start making a defensible base.  Expect a counter-attack so you're really digging in by now.

Run patrols out of bases to secure the surrounding area.  Aircraft, wheeled/tracked/hover land vehicles, foot patrols, etc.  Build smaller bases as satellites around the larger bases, run patrols out of them.  Keep supply routes open between them.  The enemy may hit one and you'll want to get more troops, ammo, medical out to them safely.  Enemy may actually be going for the support routed to the attacked base so the attack may just be a feint.  Lots of story material here....

9) Keep feeding the bases with more troops and supplies.  From here establish or maintain communications with the local gov'ts, encouraging them to accept they've been taken over.  Start using local resources for your troops (think warlords in Somalia).

Weapons could be radiation, High Freq, explosive, gas, bio, whatever you like.

I hope this helps.  (I really need to cut down on the video games....)

[von der Tann]

This is pretty much while I'm still in the 'working things out' stage of planning.  I remember when I first saw the re-imagined Battlestar Galactica, complete with Baseships nuking Caprica and I thought that's how you assault a planet.  Unfortunately nukes don't allow for some of the more sublime parts of the human drama where combat is concerned, namely the emotions you get from those engaged in close-quarters fighting.  I want that in the novel, so the nuke element is going to have be a little muted.  Of course from a realistic point of view, if you've got loads of nukes while attacking a planet, you're going to use them.

What I miss so far is one option. Did no one ever think that the defending world also has space craft? If you want the nuke thing in your story, maybe you should go with boarding actions for the "human drama and emotions" in close combat. If I had the resources I would fight the enemy far away from my home turf BEFORE the bas****ds can nuke my home.

Although maybe the boarding action might be a bit overused ...

Just my humble opinion ...

[ErikB]

Land, moon, asteroid, and space based interception missiles.

Remember the Machinekruger (SF3D) space-suits?  Looked like guys for landing on and disabling (or hacking?) orbital defense platforms.  That could be a really interesting scene to write out.

[TheMightyFlip]

Fleet based operations to take out any enemy ships or satillites, boarding actions on any space stations.

Use strike craft on ground targets while drop ships deploy ground forces, mass infantry and armor drops. Use special forces units to take out key targets, radars and the like.

If its a full planet wide invasion your probably going to need everything, including boats if there are oceans.

[SBMiniaturesGuy]

There's a FASA boardgame that's now back in print called "Prefect" and it's focused around planetary invasions with full combined arms -- space support, dropship landings, etc. Might be worth looking at for some ideas:

http://www.renegadelegion.com/addlpages/prefectpack/prefectpack.html

Also consider that you don't always have to force the beach head like D-Day -- you can't get that kind of defenses planet wide, so an invading force may very well beachhead in a lightly or undefended area. Especially if they have grav vehicles, since that gives amazing mobility.

[madmike]

Once an enemy system high ground is held, outlying bases, jump point defences and insystem enemy fleet elements all captured or neutralised, then pinpoint targeting of primary system orbital defences (defence stations, highports etc, PDC's, airbases etc) by HV kinetic projectile weapons would be critical. Since these are static, they can be neutralised with some degree of accuracy. Orbiting ships can avoid incoming KEP.

Once orbits are secured, then the real invasion begins. This would be with a combination of marine strike units and ground attack aerospace vehicles which could carve out a planetfall. Once that is done, then regular army can be used to carry the battle outward from a secured area of operations.

Marine strike units would also be reinforced by carrier based fighters and ground attack boats (later ground based once a secured dirtside base was established). There would be fire support armour, APC's and artillery as well landed as well.

I would imagine that any endeavour such as planetary invasion would be a costly exercise in both materiel and troops.

But once planetary orbit is controlled, fire support from orbit would be overwhelming to any regulary ground based defenses.

For some good books, apart from those mentioned earlier.

Lost Fleet series - Jack Campbell
13th Spaceborne - Rick Shelley
Starfist series - David Sherman and Dan Cragg