cralkhi wrote:On further thought, I suppose the real question is why the 4th Imperium went the super-militarized defense route at all. They apparently knew about the Achuultani from Day One (being descended from the remnant planet of the 3rd Imperium; given what's said about the centrality of opposing the Achuultani to them, apparently they didn't lose the knowledge as Earth [or Pardal] did) - if so, if they got to design their technology / civilization from a pretty early stage in light of knowing about the Achuultani -- why take the "ridiculous military buildup to defend immobile planets (aka targets)" route at all? We know that planetoid ships can act as generation ships, after all... I can see keeping their homworld (Birhat) inhabited, since people wouldn't want to leave & for cultural reasons, but if you know there's a big threat out there, why colonize planets at all? Why not just build/colonize permanent 'generation ships'/mobile space colonies, living around suns (for solar energy, asteroid/comet resources etc.) but capable of interstellar travel whenever needed, so they can just move away from any threat?
If the Imperium had followed that route, the Achuultani [or anybody else] couldn't become a civilization-ending threat without literally squatting on EVERY one of the hundreds of billions of star systems in the Milky Way (to monopolize the resources) - actually, it might be flatly impossible, as "core taps" seem to draw energy from hyperspace, so a space colony could just sit somewhere in the intergalactic void, powering its "sun" by core tap - needing no fuel, and thus having no dependence on any *place* in the regular universe. Core taps' control systems might require fuel, however.
It'd be incredibly hard [or impossible, if the core-tap trick would work] to threaten the species/civilization as a whole, since every colony/ship would be an independent 'world', and they could be scattered all across the galaxy (and possibly into the Magellanic Clouds or beyond, depending on whether Imperial ships can do continual FTL travel for thousands of years -- and maintain life support, but given that Dahak could restore his, I think that's definitely within their capability; plus, the Aku'Ultan used an intergalactic 'generation ship' to reach the Milky Way).
...Such a plan wouldn't even require them to abandon all the other potential (lower-tech) victim species of the Achuultani, as they could just take such species with them (or give them the tech to build their own colonies/ships). So I really don't see any downside except as a matter of honor.
Because Humans don't seem to be build to run away if there is a choice. This would make humanity a race of refugees that is restricted population wise to however much the ships can support. Those ships become nations all by themselves, their crew would end up having loyalty to their own "nation" above all else and would likely not risk their home to protect another ship. What's more is that those planetoids will wear out, and eventually will require replacements if not due to wear and tear due to losses and a planetoid wont be able to build a planetoid.
Having a million planetoids might seem like an overkill but at the end of the day the Imperium had to protect thousands of planets and guard the "traditional" approach and still protect all other borders in case the enemy decided to be sneaky. Humanity escaped complete destruction by the skin of its teeth during the last invasion, there was no way of knowing if the ships that they fought were the only enemy field force or there were more of them around and keep in mind that up to the time of the Empire Humanity has rarely if ever come out on top in a war with the enemy. And I would venture to guess that if human space was invaded that the end goal would be to defeat the invasion and trace it back to its origin and end the war once and for all.