What would you find in a planetary assault force?

[frontal assault]

I'm working on a science-fiction novel, the planned end of which is a massive space battle and planetary invasion.  I'm also trying to bring this off in miniature form, simply because it strikes me as being easier to write the battle, when you can visualise the events you're describing.  So I'm wondering what would be in a planetary invasion force, in terms of the initial assault forces and the following waves of reinforcements.  I've already decided on Paratrooper-style forces as part of the initital assault, but given that everything has to be carried aboard ships, would it be better to go with simple infantry supported by fighters and gunships, or are tanks and walkers appropriate?

[colin_baillie]

That's a hard question if you're looking to do something different. Is it humans invading a human world? What tech level are you using? Or are there aliens involved?

[Hauptgefreiter]

WH40k has something on this topic, if this is interesting for you...

I've already decided on Paratrooper-style forces as part of the initital assault, but given that everything has to be carried aboard ships, would it be better to go with simple infantry supported by fighters and gunships, or are tanks and walkers appropriate?

Well, D-Day wasn't done just by paratroopers, they brought also in the heavy stuff. I'd guess that a planetary assault force has its means to get their tanks from the orbit to the surface

[Commander Vyper]

Heavy bombardment from space on the larger concentrations of troops, hit stategic targets, and use smaller striketeams (drop troopers and dropships) to secure orbital and ground based docking/space stations and supply routes, then secure the 'beachheads and move planetside with the heavy ground support, and support the ground pounders with air fleet.

That's what I'd do anyway...

[dijit]

Heavy bombardment from space on the larger concentrations of troops, hit stategic targets, and use smaller striketeams (drop troopers and dropships) to secure orbital and ground based docking/space stations and supply routes, then secure the 'beachheads and move planetside with the heavy ground support, and support the ground pounders with air fleet.

That's what I'd do anyway...

Ditto. Bombard to keep the defensive forces heads down, strike teams to capture space ports to bring in the heavy support and then Chuck Norris to take on anything too nasty for the other stuff.

[CptJake]

Do some research on beach landings and airborne ops in our world, and I think a lot of the ideas would apply.

For example, some recon force, be it guys who infiltrate or robotic sensors getting set would be likely (like pathfinders or the UDT guys) to confirm soil conditions and enemy dispositions for a landing, as well as to emplace 'markers' to guide in the initial assault.

First wave will have the responsibilty of securing a site for the main landing.  Depending on the threat and terrain that includes clearing away all enemy assets that can influence the drop site/landing site.   They'll want to be mobile, strike hard, but won't be too heavy.

You'll likely need engineers or their equivelent early on to repair any damage done to the landing site, or make hasty improvements to allow whatever is going to bring in the main force to land their gear safely.

C2 assets must get in early to organize forces as they arrive, and communicate conditions on the ground to waiting forces.  Kind of like the marine's 'beach masters'.   

Obviously the 'security'must extend to the orbitals and the insertion point into system.   

Just some quick thoughts...

Jake

[revford]

Starship Troopers, the book that is, would be a good source of ideas.

They include men shot out of cannon at the planet, along with decoys to stop them all being splattered by flak.

Also this.

[VoodooInk]

Heavy bombardment from space on the larger concentrations of troops, hit stategic targets, and use smaller striketeams (drop troopers and dropships) to secure orbital and ground based docking/space stations and supply routes, then secure the 'beachheads and move planetside with the heavy ground support, and support the ground pounders with air fleet.

That's what I'd do anyway...

This was my plan as well. Looks like I may need to secure my communications network!

[therepoman]

I think the important question needs to be asked; why are they invading the planet? What strategic or military resources does it hold?

What is the enemies composition, and what is the force doing the assault's background?

All of this would have serious impact on the type and make-up of the forces committed.

[Inso]

Heavy bombardment from space on the larger concentrations of troops, hit stategic targets, and use smaller striketeams (drop troopers and dropships) to secure orbital and ground based docking/space stations and supply routes, then secure the 'beachheads and move planetside with the heavy ground support, and support the ground pounders with air fleet.

That's what I'd do anyway...

Yep, that about sums it up. 

The above would be a general, cover-all, planetary assault force with varying amounts of each component depending on situation.

Alternatively, if you take the A.I. approach you could drop in wave after wave of robotic troops in drop pods and let them do all the hard work.  They could create all the beach heads, hold them against attack and clear the areas for landing ships etc.  If there are aerial drones in the mix, you have your air support and anti armour weaponry.

Failing that...if it is invasion for resources that aren't affected by viral bombardment...

[gamer Mac]

Do you not need to land some big four legged walkers, supported by small two legged scout walkers, to take out the enemies force field generator.
Beware you need to watch out for the small speeders with harpoon guns, that may trip your walkers

[Commander Vyper]

Goes without saying, hence the orbital bombardment and strike teams to bring down the main shield power generators silly!

[Faust23]

GURPS Traveller Ground Forces goes into good detail about what goes in to an orbital envelopment/invasion.

[frontal assault]

Some fantastic ideas here.  When I originally thought of what a planetary invasion would look like it was primarily the Star Wars option, namely of armies duking it out for months on end over various strategic planets.  However the more I thought about how an interstellar campaign might go, the more it made me think of the U.S. Navy's campaign against the Japanese in World War Two.  Basically here the planets are like those islands, you need to take them quickly and move on.  Of course the way to do that, massive naval bombardment, didn't always work out, as in the case of Tarawa.  In addition I see each planet being heavily defended with orbital platforms supplementing ground-based systems and whatever naval forces are stationed in the area.  Therefore attacking strategy would involve fleets blasting their way though these defences, so that assault ships (or something similar, I still haven't decided on this point yet) can deploy Marines by the tens of thousands in a kind of mass paratrooper assault (though Futurama style is an amusing prospect).

I noticed Revford mentioned Starship Troopers, which along with Peace and War remains one of the two best Military Science-Fiction books I've read.  However in both books, infantry is the dominant unit with fleet providing support, and given the vulnerability tanks face in urban combat, I wasn't planning on using them (this point is again still to be decided on, but if I do go with armoured support it'll probably be some sort of walker).  As Therepoman pointed out, I was a little vague on some of the specifics and the reason for this is because I haven't worked out the scale of the action to my satisifaction.  By this I mean the size of forces, the numbers invovled and the dominant method of warfare in the book.  However amongst the things definitely decided, they will be no large scale use of automated combat units, as I really want to emphasize the human factor in the fighting.  For the moment I'll be considering the points you've all made and use them to help me work out the exact makeup for this big battle.  Please feel free to continue contributing ideas though.

[Chief Lackey Rich]

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.