A fortress world is a planet in a system that is somehow a choke point for enemy forces. A system that enemy fleets can not avoid, so they must go through it. As such, the entire world is dedicated to holding the line. To making sure that the enemy does not pass through.

But what happens when that function is no longer useful ?

For example, the xenos that this world is a fortress against get wiped out. Or the warp storms that make that system a choke point dissipate, allowing fleets to go around the system.

I'm figuring it might take a few centuries for the Imperium to notice and start to do something. But what happens then ?

I believe then planet will be reevaluated with arcane rites of Administratum Clerks, planet will be reclassificed and new tithe will be instituted. Some military forces will be withdrawn.

Is there any more information about that ?

Or examples of the process happening ?

I know it's likely to be different from world to world, but some examples of the possibilities are useful. OR any worlds being transitioned from one classification to another (excluding worlds being transitioned to dead worlds).

Because I imagine an increase in the tithe, probably from aptus non to something is likely to cause some unrest.

I'm thinking of running a campaign set on a ex-fortress world that is being transitioned into another type. Probably with some disagreement over what the world should become, with each faction of the Imperium who is interested already moving in.

- Some want an agri-world. Which means caring for the environment and shutting down polluting manafactorums that were a vital part of the defence plans.

- The ad-mech want something to compensate them for the destruction of the manafactorums.

- Others want a Shrine world due to some famous battle. Pilgrims have been since the battle and were doing so even when the fortress world was still useful as a fortress.

Probably disagreement and confusion within each faction. Eg some members of the Ecclesiarchy support the Shrine world idea, some question the purity of the place, some are willing to let this planet go in exchange for something else on some other planet.

PCs are on this world for backstory reasons and thought it a nice, comfortable world to live out their lives on. Until they get recruited into the Inquisition.

Sounds like a cool idea and sounds like you've got the main points lined up already.

I say go with your gut on this one.

Well, point is it's hundreds years to meditate different factions, who is intrested with questioned world and so on. I can offer a way how it's happens, but it's kind of logic and reconstruction (you can say "speculations"), not something can be pointed in canon. Tell me if you're intrested.

I kind of like the idea that fortress worlds don't transition into something useful when they've served their purpose. The Imperium continues to spend untold resources and manpower fortifying a position that is now useless for like a thousand years before anyone notices. You'd have a world that was a military dictatorship instilling constant fear and vigilance of a vague threat that will surely come any day now.

Efficiency isn't really how humans do things in the far future.

Well, point is it's hundreds years to meditate different factions, who is intrested with questioned world and so on. I can offer a way how it's happens, but it's kind of logic and reconstruction (you can say "speculations"), not something can be pointed in canon. Tell me if you're intrested.

Even speculation would be useful.

Efficiency isn't required. But the Imperium still needs to be able to adapt to changes eventually, even if it does so in a rather slow and inefficient manner. Consider the two approaches below for the fortress world of Brick defending against a xeno species known as the Splats:

Inefficient method: News reaches the part of adminstratum that manages Brick about the successful crusade against the Splats having driven them extinct. Some good cheer, but that's all. Maybe they don't know that Brick is only a fortress against the Splats. Or maybe they don't hear of the victory at all. So nothing changes regarding Brick. At some point the Imperium would need to decide between sending resources to the useless fortress world or to somewhere where they face a more pressing threat. Then they notice that the useless fortress world is still holding the line easily, so they reduce supplies to it even more because they are needed elsewhere. Then they start taking things that were shipped to the fortress world back. Then they start on things produced by the fortress world (eg, its military forces). At some point somebody notices that the 'fortress world' is exporting soldiers, not importing them, so they start the ball rolling on figuring out why. Records are dug up from archives, Brick is found to no longer need to be a fortress world, and the process for reclassification changes.

Efficient method: News reaches the part of adminstratum that manages Brick about the successful crusade against the Splats having driven them extinct. They immediately know that Brick is no longer useful for its official purpose, so they begin reclassification much sooner.

The inefficient method is how I expect the Imperium to react. It relies on somebody noticing that Brick isn't behaving as a fortress world should and saying something to someone who will care, so there is the possibility that it might stall indefinitely. But it's likely that the Imperium will eventually notice and do something.

Well...

Sometime some noble (magos, cleric, Peer of Imperium) will decide that fortress world can be used more effective to the Holy Deed of Improving Humanity State (read "Peer of Imperium personal profit"). So he uses his Influence to initiate reestablishing planetary status (and take a lot of long-prolonging drugs).

That question going to subsector level, then sector, segmentum. Everywhere comissions arise, that travels to said planet, looks at it, writing long, long reports, that are going up from chain (lost sometimes, so Administratum forced to repeat commision, at once - that means 10-15 years). So after segmentum level sanction papers going Terra (and let's say we're lucky and papers will not happen lost).

On Holy Terra this paper will accounted and put into queue. Imperium have armies of clerks on Terra, so soon (25-50 years) this papers will be circulate around countless scriptoriums, from one Ministry to another. Then gears will be activated. From Segmentum that planet current (well, 10 years current) state of that planet. Dozens of clerks will create new tithe for the planet (quite often after all efforts it will be set random), military command relocate some regiments.

Son or grandson of the Peer who started all this will be, maybe, appointed as new Governor. And he will suppose to decide what will he do with all that old bunkers. Well, you never can have too many bunkers - can store some harvests of potatos and wheat here. Some childs will play in closed shelters, and some military bases will be a basis for new cities.

But common man will be expected to give everything to Governor as he supposed to do when all his work went into military budget. So he will not notice something change but lesser soldiers and some military installations closed. Well, maybe he will notice taxes dropped - military took everything, and new lord can be kinder. But I won't take my money for this account.

Yes, the planets noble families will disagree over what is to become of the planet. Some want what's good for themselves, some want what's good for the Imperium, some are idiots. The last noble who spoke up in favour of the planet remaining a fortress world suffered an acute case of exploding head in the middle of his speech.

I'm thinking I can have enough of a mess if the disagreement is just between an agri-world and a shrine world.

And he will suppose to decide what will he do with all that old bunkers. Well, you never can have too many bunkers - can store some harvests of potatos and wheat here. Some childs will play in closed shelters, and some military bases will be a basis for new cities.

I'm thinking that there are a lot of farmhouses that used to be bunkers.

Yes, the planets noble families will disagree over what is to become of the planet. Some want what's good for themselves, some want what's good for the Imperium, some are idiots. The last noble who spoke up in favour of the planet remaining a fortress world suffered an acute case of exploding head in the middle of his speech.

Oh but of course. It's subsector-sector-segmentum stages.

What happens to a fortress world after its no longer needed for defense probably depends on if the world has anything else of value. If it has mineral resources then it could become a mining world and perhaps even gradually become a forge world. If it had a lot of military production then it might retain that purpose but rather than the produced weapons being used in its own defense they would be shipped elsewhere.

If the battle lines shifted away from the world but are still nearby or if the enemy pulled back the world may continue to serve as a staging ground for counter attacking into enemy space or even for launching a crusade.

If it is still a choke point based on warp routes it could be useful as a trade port/pit stop for ships passing through the gap. Either rogue traders and the like stopping off before leaving Imperial space or perhaps the Imperium has taken worlds on both sides of the choke point and it is just a convenient place for goods from each side to be swapped.

If the world has no real value anymore then it would probably slowly die like an old west mining town where the mine has run dry. Essentially becoming a run down lawless frontier world.

I'm thinking I can have enough of a mess if the disagreement is just between an agri-world and a shrine world.

And he will suppose to decide what will he do with all that old bunkers. Well, you never can have too many bunkers - can store some harvests of potatos and wheat here. Some childs will play in closed shelters, and some military bases will be a basis for new cities.

I'm thinking that there are a lot of farmhouses that used to be bunkers.

Might be better to go mining world versus shrine world instead of agri world versus shrine world. I can't imagine the environment of many war torn fortress worlds being in good enough shape to support significant agriculture unless it has been a very long time since it was last invaded.

It probably get's repurposed as an imperial guard/ shola progenium training ground.

Or as cps said it becomes a lone sentinel guarding against a threat that never comes, slowly turning paranoid...

Or the inquisiton turns it into a (not so) secret base...

Or it gets turned into a resting home for retired Cadian veterans. (This is an obvious joke: there is no such thing as a retired cadian soldier )

In any case it's still Ork bait. (They see heavily defended worlds as a chalenge and an invitation!)

Might be better to go mining world versus shrine world instead of agri world versus shrine world. I can't imagine the environment of many war torn fortress worlds being in good enough shape to support significant agriculture unless it has been a very long time since it was last invaded.

Good point. I'm thinking that, while it's been at least 200 years since the xenos it was a fortress against went extinct, it hasn't seen serious battle for longer than that. First it spent some time holding off attacks. Then it was a fortress just in case the xenos decided to try one last kamikaze attack against the Imperium once they knew their defeat was certain. I'm waiting for Enemies Without before deciding the specific xenos species I'll be using, so all I can say for sure is that the final attack either never came.

Then there is the ad-mech efforts to repair the ecosystem.

Then there is the ad-mech efforts to repair the ecosystem.

Admech repairing the ecosysthem? LOL! That'll be the day. I'll bet their definition of "ecosystem" is "anoying thing that gets in the way of production."

Then there is the ad-mech efforts to repair the ecosystem.

Admech repairing the ecosysthem? LOL! That'll be the day. I'll bet their definition of "ecosystem" is "anoying thing that gets in the way of production."

The Ad-mech aren't repairing the ecosystem for free. The groups who want an agri-world want a food producing ecosystem. Those wanting a shrine world prefer the air to be breathable. So they are both willing to give the Admech something in exchange.

Maybe the players get sent there to commandeer all remaining weapons and ammunition and strip down any usefull equipment from the now obsolete world.

Problems might arise when the locals don't want to give up their stuff: maybe because they have gone paranoid or have seen omens that an attack is imminent.

Or maybe the extinct xenos come back one day. Not a force of survivors but the actually dead aliens; Picture this: an entire race of xenos, slain in the wars of the imperium reanimated as legions of evil spirits by the fell powers of chaos!

Maybe the world was garissoned by Skitarii and other admech troops who left a host of (combat)servitors behind as a fully automated defence force. And after all these years, their programming might have deteriorated...

AM certanly can get an idea about "that stupid bags of flesh works more efficient when they have air, food and water; they're not very useful but they're more useful alive then dead".

And they need very big stream of raw materials and foods arriving.

The Ad-mech aren't repairing the ecosystem for free. The groups who want an agri-world want a food producing ecosystem. Those wanting a shrine world prefer the air to be breathable. So they are both willing to give the Admech something in exchange.

Makes sense. Altough i doubt the imperium even has any such technology...

Maybe the players get sent there to commandeer all remaining weapons and ammunition and strip down any usefull equipment from the now obsolete world.

I specifically want the player characters to have each arrived on the planet for their own reasons and decided that it wasn't worth trying to leave. So they decided to settle here because, while nicer worlds exist, this world is nice enough that those nicer worlds aren't worth the effort it would take to get to them. Then they each choose to do something that they consider the Right Thing To Do knowing that it will probably lead to them personally suffering. At best it will be forgotten.

Then they get recruited into the Inquisition.

Also: http://wh40k.lexicanum.com/wiki/Magos_Biologis

Well, a massive fortress world is probably going to feel pretty safe, even if it isn't. That's a good reason.

There's a lot to learn about weapons there, probably a bit of tech-heresy going on with maintenance and black market trading of military grade hardware.

Probably a fortune to be made in gambling...

plus other ideas that I've forgotten now that this "Reply to this topic" field has been open for over an hour.

Well, a massive fortress world is probably going to feel pretty safe, even if it isn't. That's a good reason.

When talking about how safe a world feels, it's best to divide threats into two categories:

- Threats to the Imperium. Things that the Imperium is trying to protect people from. How threatened people feel from them depends on how much they know. For example, the Inquisition suppresses knowledge of daemons, so most people wouldn't know enough to worry about them. In the case of this planet, the only one of those threats that the public know about are the Orks, and the propaganda says that the PDF patrols are keeping them under control. Yes there are other planets under attack from other Xenos, but those planets will hold the line and defeat the threat over there. Yes there is some heresy on the planet but if everyone stays vigilant then it gets swiftly stopped.

- Things which don't threaten the Imperium, so the Imperium won't do anything about them. For example the environment of a death world, gang warfare, brutal enforcers coming down on anyone who looks at them wrong, etc. The average human living on one of those planets will feel threatened by those things. On this world, those dangers are much less.

Looking at the backgrounds I can suggest backstory seeds for most of them, but I can't come up with some ideas that would work if a PC has an Adepta Sororitas or Mutant background. I'm not sure if I'll allow a mutant PC.

I'll be using the following suggestions if I player picks a relevant background.