another big mrxak topic

It's that time again, folks...

Here's some past topics of discussion, feel free to bump any of these if you have anything to comment. Despite the original themes, many of them went on to discuss other big ideas in science fiction and plug-in development, so be sure to check them out if you missed any.
Space Travel and Governments
Population Growth and Economic Evolution in a Space-Faring Civilization
Government Systems and Politics
On Relative Sizes of Spacecraft
Economic Systems and Space Corporations
The Downfall of Civilization

This topic will be about military hierarchies. The idea is to discuss various systems and hopefully help plug-in developers and storywriters figure out what sorts of ranks people might earn, or who people might talk to as part of a story, while advancing through it.

Military Hierarchies
Militaries are generally, minus some occasional politics and corruption, the only true meritocracies in existence today. People gain power in a meritocracy through skill and accomplishment, which makes for an efficient and capable fighting force. While it's true historically that the wealthy classes would hold officer positions while lower classes would serve as enlisted personnel, and even today there are political systems which reward party loyalty more than merit, many militaries around the world have officer candidate schools that recruit from the enlisted soldiers, field commissions do occur, and advancement up through the ranks in both the officer and enlisted categories is accomplished through showing merit.

When it comes to storytelling, one has to decide several things. How does the political climate relate to military promotion? Does the political system in place interfere frequently with high level military appointments and promotions, or does the military handle such things internally and independently? How easily do soldiers move up from enlistment to becoming commissioned officers? Was every officer once an enlisted man or woman, or is there a direct route to a commission? One should also not forget warrant officers, which fit between enlisted and officer, and often play an important role in the operations of militaries. How do warrant officers reach their position, and do they routinely earn a full officer commission? How political does the awarding of certain medals and honors and ceremonial positions get?

Next, one should also decide upon the ranks themselves. Thanks to the likes of Star Trek and others, we've come to see space as another vast ocean, the spaceships, ships, and thus use naval ranks in much of our science fiction. Is this most appropriate for your story? Would an air force context be more realistic, as air forces tend to be where we get our astronauts? Instead of a Captain leading a ship, how about a Colonel? Air force ranks also avoid some unfortunate analogs, such as the seaman recruit being the lowest ranked sailor, not exactly the best name for the lowest rank in a space navy. There are handwaves for this, such as "crewman" and "spacer" and in some cases a mix of marine ranks for enlisted personnel to get you "private". Plenty of stories avoid the issue altogether and just don't have people of those ranks ever mentioned, but that's sort of cheap.

Speaking of marines, does your space navy have them for ground combat and ship boarding, or do the same people who fly the spaceships fight in close quarters too? Do you have all the usual branches of military might, with either space as a new branch or as part of another branch? When your space fleet arrives to conquer a planet, are they dropping battleships into the oceans and airplanes to patrol the skies, and tanks to cover the land, each with its own separate military command structure? Do you unify all the military forces into one hierarchy, and if so, do you mix the ranks together, or choose one naming system and run with it? Are there joint commands, or are they carefully isolated? How are special forces operations conducted and commanded? Have the military branches changed, over time, with branches merging or splitting? What consequences has that had for rank names and structures?

How does the military fit into your government? Is the military the government? Is there strong or weak civilian control over it? Is there strong support or opposition to the military within the civilian political systems? Is there a separate department or cabinet position for the military command structure, or multiple such positions for different branches of military? Is there a military supreme commander of forces who takes orders from the chief civilian(s) of the government, or is the civilian leader of the government the direct boss of the troops by way of various individual commands? What sorts of orders and decisions can be made at various levels of government and the military hierarchies?

That should hopefully get the ball rolling. I may expand this out to various political civilian systems, and command structures for things such as disaster relief, organized crime, and governmental appointments like "drug czars", but I wanted to focus on the military to start. Feel free to preempt me and start talking about those things before I get around to it, and any other topic you think relates or is interesting.

IMO, the space branch of the military should be its own branch; the air force was created rather recently with the invention of the airplane. Before the airplane it was just the army and the navy. It needs its own rank system just to fit with the others. However, the ranks and advancement system can be analagous to army/navy/air force.

Regarding marines, I would argue that a crewed ship needs them. Redundancy not only in the mechanical parts of the ship but in the crew itself is important for allowing a ship the option to keep fighting after taking losses. If the crew fights, then there may not be enough people to run the ship while until the crew finishes fighting and returns. What if you board a ship to capture it, and then its friends show up (who you had not detected before)? You need to be able to run the ship while fighting in close quarters.

From a technical perspective, a planet invasion needs airplanes, tanks, and other vehicles. Long-distance spaceships will not be practical for ground or in-atmosphere combat. Joint operations on the ground will proceed similar to how they do now, with the spaceships providing reconnaissance, supply drops and possibly orbital strikes.

@mrxak, on 26 October 2011 - 03:29 AM, said in Military Hierarchies:

... we've come to see space as another vast ocean, the spaceships, ships, and thus use naval ranks in much of our science fiction. ... Would an air force context be more realistic, as air forces tend to be where we get our astronauts? Instead of a Captain leading a ship, how about a Colonel?

There’s also the rather interesting example of Major Davies in Escape Velocity ’s rebel storyline, who is later promoted to Admiral.

@mrxak, on 26 October 2011 - 03:29 AM, said in Military Hierarchies:

Do you have all the usual branches of military might, with either space as a new branch or as part of another branch?

Of course, many modern military forces have already done away with the idea of branches.

I forsee the structure functioning similarily to the current Canadian Forces. On one of our warships, we have Navy personel to run the ship, and anything that flies is run by Air Force people (though we only carry helicopters on our ships). Then we also have a 'boarding party', which is Navy people who do extra combat training and thus are in charge of ship vs ship combqt, as well as helping with the operation of the ship. Incidently, this is similar to the way Battlestar Galactica portrays things. The main reason I think this makes the most sense is because any large vessel will have the same internal atmosphere as a sea going vessel. The medium it travels through isn't what really distinguishes it, but the type of working environment. Similarily, a space fighter environment would be very similar to our current fighter jets environment.

Now, to take over a planet: it seems like very inefficient use of space onboard the carrier to have large land or sea going vehicles, which can only be used on a planet, rather than carrying a larger number of fighters and transport craft, which can be used for both planetary and interstellar combat. Thus, the primary strategy, I would think, would be to establish air superiority, then drop troops, perhaps with small jeep or humvee analogues, to secure key locations. Primary enemy neutralization would be through air support, which would, presumably, have significantly improved staying ability in the battlefield than our current fighters.

@jalisurr, on 26 October 2011 - 11:14 AM, said in Military Hierarchies:

On one of our warships, we have Navy personel to run the ship, and anything that flies is run by Air Force people (though we only carry helicopters on our ships).

And ‘Navy’ and ‘Air Force’ mean little more than ‘the people who run ships’ and ‘the people who run aircraft’. They’re not completely separate forces like the Royal Navy and RAF, although they do preserve different names for their ranks. A number of European countries have done the same, and even Britain is looking at the possibilities of a merger.

I think the Navy might be a natural extension into space combat due to, as mentioned, similar operating environment. Of course, it would have to be changed a great deal, possibly either by splitting into a new branch or by evolving the Navy. Partly, this is because I see naval forces becoming largely obsolete in interstellar warfare. Not all planets have a liquid environment, and those that do won't always have one suitable for your sea-going vessels. On the latter reason, take for example ships float because they are, as a whole, less dense than the water they're in. What if you put that boat in a fluid that's less dense than your boat? It sinks. What if the fluid is much denser? Your boat may try to float too high out of the liquid which, at best, would mean more of it is exposed above the surface. At worse, the engines wouldn't reach the fluid to propel it or it'd bob out and tip over.

Additionally, when you can orbitally insert ground and air forces from any point above the surface (barring enemy interference), you do not need to worry about getting in a boat to cross an ocean, you just fly. The only times naval forces would be preferred is if you're invading one of those civilizations that love to live on the surface/under oceans, in which case if you can't simply bomb them from the skies/orbit, you'd need to come up with alternative solutions in order to deal with them. Custom made naval vessels would be one solution, but a potentially expensive one, so even then a Navy may not be viable.

I think space would be the natural outgrowth of the Air Force, but in my opinion, it would also likely adopt something of a Naval structure, possibly through a merging of the two branches. This personally makes sense to me in terms of that in interstellar warfare, you'd like see something analogous to an aircraft carrier or destroyer in space, as opposed to the more fighter, bomber, reconnaissance, and transport craft that the Air Force tends to maintain. In this regard, I think you'll see a merger of the two branches. The Air Force will be developing the technology to go to space, while the Navy will likely be the ones who have the protocols and systems to really run such a thing. BSG and Trek both have something of this kind of a philosophy towards their chain of command and their operations, for example.

I think specialized ground assault vehicles are probably redundant. Thinking like an engineer, I'd be leaning towards a combination craft that is both amphibious and atmospheric. It needs to fly, drive, and swim, essentially. There's not a terrible difference between designing a craft capable of aquatic settings and one for spaceflight, and the next key is to figure out how to give it some wheels as well. In terms of artillery, orbital bombardment would probably be the more logical air support method.

The military is a delicate balance between civilian oversight and independence. This is the same difference between the military and the police. The military needs to be responsible for the enemies of the state, while the police needs to defend against the enemies of the people. When the military becomes the police, the enemies of the state tend to become the people. Thus, it needs enough independence to carry out its duties, but if it achieves too much independence, it can turn in on itself and against the people it should be defending. This is truly the purpose of the Second Amendment, not this "constitutional carry" BS so people can walk around with handguns wherever they feel like. The idea is to make sure that the military is not the only one with the weapons, and that there is always civilian oversight or at least comparability to the military in capability, as well as to give the military assistance in times when local militias are required for the defense of the general welfare.

Because the military needs to achieve this delicate balance, it is also left open to the possibility of politics and wealth becoming a factor in promotion and appointment instead of truly being a merit-based organization. Those at the top, who make those decisions, are not immune to the social ladder. Thus, it may not always be what you know, but who you know as well. On the whole, however, our military and I think most modern militaries, are generally built of those who have started at the bottom and worked their way up, and to this I agree. I believe that people should start as a deckhand. This teaches humility and also brings a sense of understanding to what those subordinate to you have to do. I think a person who has served as a grunt infantry is less likely to send a platoon of infantry to their deaths, because they'll have had the experience necessary to remember what it was like to be that grunt. They'll manage their assets better, in other words.

Why have wheels when you can just hover above the ground? That is, assuming that using up fuel isn't a concern.

@jalisurr, on 26 October 2011 - 10:32 PM, said in Military Hierarchies:

Why have wheels when you can just hover above the ground? That is, assuming that using up fuel isn't a concern.

War has developed around the ground soldier. The infantry's task has been (and will be) to take, hold, and protect an area of land. The navy was developed to bring the infantry to distant lands, or stop enemy infantry from invading by sea. The air force fills a similar role (but with close air support and bombing - mobile accurate artillery - thrown in). Unless you are invading a planet of birds or fish, there's no reason these roles will change much.

When defending a planet you have resources on, fuel and vehicles are not a concern. You can build and fuel whatever you want by using the resources of the planet. When invading, fuel and vehicles are a concern (you need to transport or capture any fuel and vehicles you need) and then wheels are better than hovercraft. Assuming your orbital strike capability from the spaceships is very precise, you don't need airplanes for ground support. You do, however, need airplanes or very good AAA to enforce air superiority. You don't need a navy if you have a transport system that can launch things from the spaceships, return them to the spaceships, and launch them again without too much hassle.

If you manage to invade a planet and immediately manufacture all the fuel you need to use hovercraft instead of tanks, the defenders aren't doing a very good job.

There are other reasons for using ground vehicles instead of hovering vehicles - namely the amount of thrust required to make something hover, the reduced durability of the engines associated with stronger engines, difficulty involved in ground soldiers quickly entering/exiting the tank or using it as cover, and that's all i can think of right now, but I'm sure there's more.
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@Kruger: if you have orbital bombardment, there's no need to aircraft in a close-air-support or bombing role, and no need for naval artillery near shore. You need aircraft and AAA solely for air superiority to prevent the enemy from bombing you. You still need an aerial transport craft to bring things to/from the spaceship, and something like a tank to provide mobile cover for infantry.

Sorry if this was a jumbled mess, I was fairly exhausted while writing this.

@LNSU: That's kind of what I meant, but I too was pretty tired when I wrote it, and upon reading what I wrote, I can see that I didn't explain myself very well on that point. I'm thinking that aerial-capable aircraft will still have a role, but I think they'll need to be designed as both space-based and aerial-based fighter craft. From there, I think there will be a more diversified craft that would be aerial-capable as well as being amphibious, with a purpose mostly being support and troop movement (similar to the MRAP vehicle being used today, only more multi-purpose.)

Another thing that I think bears mentioning is that if we develop interstellar travel, we'll have to invent more energy-dense fuels or storage mediums. Because of this, I think fuel or energy reserves are going to be less of an issue. Because our current most energy-dense fuel products are hydrocarbon based, we're very limited in range and power output. Hydrocarbon fossil fuels are not especially energy-dense, though. So, a ground support vehicle probably doesn't have too much to worry about in difference between capability to hover as opposed to be wheeled in the future, depending on what technologies come about. It also depends on if we can figure out a reasonable anti-gravity solution. The present technologies for hover capabilities are very power intensive, but they're mostly based on jet-turbine VTOL designs or on air cushions.

I think the penultimate paragraph is the most important to get fleshed out. You can usually get away with glossing over a lot of these questions, letting your universe fill itself in and writing around them. (For example, IPs like Mech Warrior can get away with a really impractical – and universal – military MO and just hand-wave it away as rule of cool. And it's still freakin' awesome.) But the question of government oversight of the military (or vice versa) is something that I find really sticks out if inadequately addressed. To use a Nova example, that's one of the things that made got me interested in the Polaris story/history when I found very little to get excited about in the rest of the governments. They really developed the relationship between the Nil'Kemorya, Mu'Hari, and the central government, and that made for some great dynamics, even if the game would have played no differently without said background. (Shameless self-promotion: this is the focus of a large chunk of Anathema Chapter 4, and it would play out very different without said background ;).)

This really dovetails with government, which is one of the things I find very lacking in a lot of IPs. Not that it's usually underdeveloped, but it usually seems rather samey. Lots of things like "Well, we'll just take Rome and put it in space," or "We'll just take America and put it in space," or "We'll just take the Delian League and put it in space." (Although sometimes this can work very well.) So I won't hammer it home on the risk of getting into an entirely different topic.

So what do people think is reasonable, practical structure for government oversight/control? I've been playing with the idea of a Sovereign Fleet, in which the commanding officers are given relative freedom of execution, since wartime communication would probably be limited – unless your universe has an Ansible, it may take days/weeks/months to get information back and forth between the front and the seat of government. This could be contrasted with a much firmer system of control, in which direct agents of the government would be present in some capacity, or simply hand-picking commanding officers who are seen as the most likely to carry out the will of the governing body. You're making a huge trade-off either way; you're either waiting for communications to pass back and forth, hampering your war efforts immensely, or essentially abdicating the civilian government's oversight for the duration, or hoping that the agent system... works at all. (This is assuming that there's no Ansible and that the military and government are not the same body. Both of those cases would pretty much eliminate these problems.)

I'd be interested in seeing what people thing of that dichotomy, since in my own little pet project, which has changed names several times before settling firmly on Shadows of Terra, most governments have been using the agent system, while one was forced to adopt the sovereign system after a civil war. Maybe some opinions from here will work they way in by proxy.

As an aside, in the case of a military that ultimately answers to a representative government, which bodies of government should have the final say? I've always just defaulted to whoever the head of the Space Executive Branch happens to be, but that's probably just because that's what I'm used to. That certainly doesn't need to be the case. Is answering to the Space Senate too clumsy for the armed forces? What about in cases like a Confederated (or even Federated, I guess) government? Could they answer to the representatives of the planet/system they're from? How do we define "from?" when we're talking about spaceships and their crews? Certainly when we're talking about system defense forces that distinction makes sense, but what about offensive warfare? Does something like a "national guard" even make sense in this context? On the offense, perhaps the local seats decide what forces to commit, after which those forces answer to a central command?

@archon, on 28 October 2011 - 05:38 PM, said in Military Hierarchies:

... wartime communication would probably be limited – unless your universe has an Ansible, it may take days/weeks/months to get information back and forth between the front and the seat of government.

Peter Cartwright talked about this as an issue in the world of EV Override. The idea is that in the United Earth navy, commanders in the field have a substantial amount of individual discretion, and therefore there’s room for people like d’Erlon to exhibit brilliance and originality. On the other hand, the Voinians have faster-than-light communications, so they are meant to feel like they’re all being commanded by a single central staff on Borb Station.

Well I'll be. I guess I can toss that one into the huge heapin' pile of things that I thought were at least mildly original that later turn out to be well-trodden ground. Although nothing will ever surpass Mass Effect in the sheer number of ideas it made me realize weren't mine.

Still, good to see that there's something to the thought.

If FTL capable ships are present, I'm not sure that FTL communications become quite as bad, but it's still the difference between the Pony Express and the telegraph, unquestionably. And, as Trek explores fairly frequently, even when FTL communications are present, who is going to know more about the current situation? The captain in the midst of the circumstance, or the desk admiral back at Fleet HQ? Your field commanders do need to have a fair bit of broad authority, even if they're in direct real-time communication with a superior. This is why I like the idea of the space fleet being a very merit-based promotional structure. You want people who have a proven track record of making those kinds of independent decisions while still upholding the kind of code of conduct that your military approves, whether that military is a Starfleet-type explorational/defense only sort of organization, or a warrior-based conquering military.

It also depends on the value of bureaucracy in your culture. If you have a cultural setup like the Vogons, where everything has to be stamped, checked, triplicated, sent back, lost, found, resigned, transferred, checked again, stamped a second time in a different color, approved, appealed, overturned, resubmitted, transferred again and finally accepted, then real-time FTL communications are a must-have and the military would be at essentially a standstill without it. If the culture is less bureaucratic, then it shouldn't be quite as bad of a problem.

The amount of frontier is also a difference here. In the case of EVO, the main battle fronts were located well into the frontier and away from the main offices, so to speak. The Enterprise and Voyager were well away from home most of the time and thus were further from any sort of superior that could be reasonably contacted. On the other hand, if a commander is patrolling only a sector or two away from the local Starbase with an admiral behind a desk, then getting in touch with the next level up isn't so much of an issue. DS9 actually played well with starting in the frontier beyond the borders of Federation space and having a lot of the independent flying by the seat of their collective pants, and ending up being more of the edge of civilized space by the end and the major governing hub for the region.

Another thing that Archon touched on is from where the culture is based. I know I tend to forget about the idea of nomadic cultures that do not have a permanent base, be it planetary or station-based. What kind of differences would a military structure take on a Battlestar Galactica fleet-style existence? Would they actually have differences? In BSG, the culture was uprooted and was forced to change its governance structure and court system due to the new existence of a nomadic space-based existence, but the military was largely unchanged. However, that was a culture that was formerly a colonial and planetary based culture. What of a culture that has solely existed in space for their history? Or at least enough of their history that their culture no longer carries any sort of planet-based cultural memory (say 4-5+ generations?) Would that change the military's hierarchies and policies?

@krugeruwsp, on 31 October 2011 - 11:35 AM, said in Military Hierarchies:

If FTL capable ships are present, I'm not sure that FTL communications become quite as bad, but it's still the difference between the Pony Express and the telegraph, unquestionably.

This also ties into another set of questions that I forgot to bring up: how long does FTL travel take, and can you send messages faster than ships' FTL travel? If you can get ships/messages back and forth in a few days/weeks, it's not as much of a problem. But if it's more of a matter of months, you're going to have complications. I'm working under the assumption of 3-5 days per jump for smaller ships and anywhere up to 15-20 days for the largest capitals for most of the militaries, plus limited access to instant hypergate travel. Additionally, you have to take into account how much space there is between a government's seat and its target. If you need to travel 20 (or more) lanes to reach your target and are limited to ship-born messages at a rate of 3 days per lane, your fleet had better have some autonomy. For large empires, or those with a lot of empty space (or another faction) between them and their target, that's a huge concern.

I'm also glad you brought up nomadic cultures, since that's another favorite subject of mine. However, I haven't put much thought into how that would change a military structure. What I have thought about is how dangerous a completely mobile faction would be, especially as the arms race accelerates. For example: how do you occupy a nation that's all on spaceships? That's like trying to invade a country where every apartment complex is armed with SAM and artillery, and the houses can just get up and leave. It could really blur the lines between civilian and military, too, depending on how you set up their social structure. Think about things like Trek, where there are usually civilians just chilling on the Enterprise unless it's clearly going into danger. (Emphasis on "clearly," since sending thousands of civilians into the line of fire seems to be standard operating procedure at Starfleet. :p) You pretty much can't launch a surprise attack on a fleet-based civilization unless you're prepared to slaughter tens or hundreds of thousands of civilians at the outset. Plus, you can't really catch them unprepared, assuming they tend to keep their ships together. As a final thought, what happens to something like the doctrine of mutual assured destruction when there are weapons that could easily depopulate a planet/system, and one side doesn't rely on planets or stars? Ugly, terrible, things is what.

Further, I agree with Mass Effect's take on it, with the Quarians' Admiralty Board being the final say in just about everything, and the official (if seldom exercised) Martial Law. With ships essentially standing in for political bodies, it's sensible that the navy and government would meld together to a greater or lesser extent, given time. (Never seen BSG so I don't know if that happens there.) Of course, it's not impossible that there would be separate civilian and military command. You could have civilian ships and military ships, or you could have the civilian and military leadership having jurisdiction on different levels. But those roles would have to be very clearly defined, or you'd have potential for a very nasty power struggle, and even with clear delineation, it would be at best risky and at worst a powder keg.

However, I think that the greater context is more important than whether they live on ships or planets. Both the humans in BSG and Mass Effect's Quarians were forced into their situation against their will. But in my opinion there's just as much reason for a civilization in the right situation to pack up and move out of their own accord. I think that in this case, you're less likely to see the strong-arm, military oriented government because that's more of a result of being hounded and (rightfully) paranoid as of living on ships. I guess you could call it a lurking variable.

BSG is definitely worth the watch for some serious sci-fi theme exploration, doubly so if you get the Ron Moore podcasts on them. I am, unfortunately, not familiar with Mass Effect at all, though I've heard good things about it. I'm simply not much of a gamer.

It's a good point to bring up in terms of using WMDs in a space-based society. If they have no values attached to planets or systems, they probably won't have as great qualms simply blowing one up. In fact, I would anticipate the development of technologies to possibly shatter a planet and mine it quickly for raw materials. Think about how much raw iron is in the Earth's core, among other rare-earth elements that would be important for a ship-based civilization?

@archon, on 31 October 2011 - 01:15 PM, said in Military Hierarchies:

This also ties into another set of questions that I forgot to bring up: how long does FTL travel take, and can you send messages faster than ships' FTL travel?

Since in Escape Velocity jump time is linked to a ship’s mass, you also have to consider how small you can make a hyperdrive. Is it possible to make miniature message pods that can jump much faster than any ship, or is a shuttle the smallest thing that can go through hyperspace? For that matter, are faster-than-light messages even based on the same technology as the hyperdrive?

I imagine purely nomadic societies would have severe issues with resources. While they may be self-sufficient in normal circumstances, combat and war would put a strain on them when they do not have ready access to one or more planets to harvest replacement resources from. They'd be reliant on stealing, salvaging, trading, or harvesting from uninhabited worlds or asteroid belts. None of those would be simple tasks during wartime when you're under constant threat of attack and blockade, especially harvesting when you're culture isn't "designed" to remain in one place for long. While they might (or might not) be trickier to attack and approach, any loss the suffer would be a heavy blow and be difficult to replace. Having your whole population on board is great if the enemy wants to avoid civilian casualties. But if they don't care or, worse, want to exterminate them outright, then it's a serious, serious disadvantage. Any weapon capable of severely damaging, depopulating, or pull something impressive and is able to outright destroy a planet should no doubt work wonders when used on a starship.

A closer real-life example would be a bunch of people living on some fully functional battleships and air craft carriers in the middle of an ocean with no life or resources except around some islands here and there that may or may not already be claimed by continental nations.

Josh – your last paragraph reminds me of part of the Stephen Baxter novel Flood , where some of the main characters survive on a Queen Mary-style ship that traverses the world looking for resources. There's also the mention of surviving US warships (mostly submarines) being used to fight off pirates and such.

I want to address the topic of hovering vs. wheels. Why not use reverse magnetism to hover? Almost every planetary body should have at least a token magnetic field of some sort, especially if it's inhabited. Therefore, it shouldn't be too difficult to use electromagnets to repel a vehicle off the ground. It could work in low-gravity situations, as well, since the magnets could even be reversed slightly to keep the craft from floating off, assuming the low-gravity body in question is magnetic at all. I'm not a certified engineer, but I seem to understand that electromagnets also use little power to function. If my understanding is correct, that would definitely be an advantage.

The possibility of using legs is also something to think about as legs would be much more capable of moving over extremely rocky terrain than wheels and wouldn't have a constant drain on energy/fuel reserves while stationary like hovering would. The legs would probably even use hydraulic systems making them largely immune to any electromagnetic-based weaponry. Only two problems come to mind with using legs: weight and speed. If the body is too heavy the legs collapse, which then requires stronger legs which then add more weight. That weight also restricts how fast the vehicle can move. Some might argue that Star Wars already showed another weakness with using legs (for those that don't know what I'm talking about, google 'Snowspeeders') but that's somewhat easily fixed by using shorter legs. After all, most predators have shorter legs or keep closer to the ground to begin with. AT-ATs resemble camels, giraffes, and elephants more than anything else with their longer legs.

While on the topic of vehicles, I agree that, once space-based craft have been established commercially, any society would probably lose all interest in sea-based craft from an economic perspective; the airplane is already circumventing water travel to an extent today. As such I wouldn't expect space-based militaries (or militaries with space-based branches) to need or even use sea-based craft. Even when combating a culture that lives on/under the sea, I see it as a simple modification to take a craft meant to survive the pressures of space travel and convert it to survive the pressures of sub-sea travel. It really just boils down to a reversal of where the higher pressure is; inside or outside the craft.