Yay for World War II stuff. Logistics are the key to any military operation. But the generals of World War I were shocked when they thought they were fighting in the 19th century. The generals of World War II were shocked when they thought they were fighting WW 1. The generals of Vietnam were shocked when they thought they were fighting WW2 (they sent tanks to Vietnam!) and so on.
So let’s pretend it’s viable or, more importantly part of your setting/campaign, and get back to the original question:
How would you handle a invasion into a system?
I figure Carlobrand has the salient points laid out. Essentially, the actual invasion of a capital system being very unlikely and very costly but the systematic invasion of outlying points/systems, resources, and blockade of said capital resulting in capitulation. The reason I agree with this being the most likely scenario is due to control of a population. It’s one of the things that makes my brain spin in 2300AD since there is no real reason for warfare when someone colonizes the same planet as you… it’s a FRICKING PLANET. You could have Australia and Canada in place with all of their populations and still have enough room to do what you wanted.
But if you wanted to control the stars, destroy an enemy or convert people to a religion then maybe it’s worth it. Science fiction, including Traveller, is full of many examples of that. Take Strephon’s Black Wars from the Rebellion as an extreme example.
Anti-gravity changes everything. Also, we can look to the examples of colonial times (falling afoul of my own argument above…) where colonies changed ownership due to wars and struggles but the locals did not really care one way or the other. They still have to pay taxes, they still have somebody telling them what to do. The local population (of a conquered people) who get conquered by someone else are likely to support whoever is currently holding a gun to their head.
On a 2300-related note, the real complication is a lack of lift/contragrav. This is what makes planetary invasions plausible in advanced sci-fi and yet subject to all of those other arguments (WW2 etc) in a 2300 setting.
So in 2300, we want to invade… how do we do it? I think a very similar approach.
1. Take outlying system object and set up supply chain. This is easier to do in 2300 than many settings due to the linear nature of FTL travel. You can put up a blockade a system out and still have an effect although it won’t be perfect.
2. Take out system objects/defenses piecemeal or isolate them.
3. Take out aerospace defenses and capital missile complexes. This is the real invasion since once you have the High Orbit/Ground, you can conduct unilateral operations against the surface. In 3rd Imperium, this is complicated by the availability of lift to anyone with an aircar but in 2300, you can take complete control of orbital infrastructure.
4. From this point on, you have several options:
a) Threaten colony into submission by nudging an asteroid over their main city and flashing an evil smile. This is likely to result in surrender but not acquiescence. Expect significant underground rebellions/extremist movements composed of any military infrastructure that existed on the planet. Since no combat occurred, military remains completely intact and supplied. Expect tanks to be hidden, missiles stashed and crates of autoguns to find their way into the rural areas to prepare for “The Day!”
b) Blockade. The time-honored method which is dependent on whether they are self-sufficient or not. As we’ve pointed out though, the population is likely to not be happy about living in the 18th century. Blockades over a solar system are likely to be costly (personnel and materiel), lengthy and irritating. Constant operations are going to play heck on vessels and crew. They are also more likely to end with a conclusion that does not involve complete control (imperial) of a planet but more governorship/overwatch/protectorate since you’re essentially getting everyone to surrender by means of economics.
c) Invasion. Granted, a planet with a billion people is a hard/impossible target. In 2300, there simply aren’t any except Earth (maybe Tirane, I forget). However, with a billion people, I’m guessing you’ll have 999,999,999 different factions. So let’s not assume it’s a monolithic military machine that is defending the place. Plenty of room here for 5th Column, politics, deception etc.
But let’s assume a more modest population of 100 million people in Australia on our alien Terra Nova planet. The rest of the planet has scattered settlements but the main colony is Down Under. Since we control aerospace, we bring in our dropships and set up a deploy zone on the opposite hemisphere from the main colony. The invader lands enough equipment to get air defenses and other equipment set up and then begins the troop build-up. Then the air assault starts… and pretty soon you’re in a good old-fashioned ground war.
Costly, nasty, and prone to defeat with no place to retreat is no way to run a war but there you have it.
However, you have the High Orbit support so you can do drops and strikes throughout the planet. You also have the build-up of forces to take and hold locations/population centers. Another advantage is that after the nasty ground war, you’ve theoretically disposed of that military infrastructure or (hopefully) devastated their materiel stores.
In the end, that’s why a GM should approach an invasion carefully… the victors have to occupy the urban and resource areas along with the population. Some effort should be spared for that thought, what is the end-game of the invaders? Do they need the whole planet or can they take part of it and hold it? Can an invasion consist of a smaller force for harassment purposes?
Politics, espionage and psyops are going to be huge in such a campaign. The invasion will be costly only to end in serious guerilla warfare unless the PR is maintained. As mentioned above, most folks will just settle down and get back to the business of business regardless of who is paying the taxes. But war crimes, evil empires and oppression are likely to result in major problems in the long run.
Bringing us back to... what is the goal here? Once we know that, it can be determined the approach that should be taken by a polity.
d) Too much trouble? Just drop the asteroid… humans meet dinosaurs.
[I'm reminded of a recent and common complaint about military sci-fi... Basically, most of it's not sci-fi. It's World War II with lasers and space ships. We use the past to build our ideas but it certainly should not shackle them. Especially in fiction or gaming.]
