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FORTS in BtS... Everything there is to know

Discussion in 'Civ4 Strategy Articles' started by PieceOfMind, Jan 27, 2009.

  1. PieceOfMind

    PieceOfMind Drill IV Defender Retired Moderator

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    FORTS in Beyond The Sword

    Everything there is to know about forts in BtS!

    This article is intended as a reference for anything concerning forts. There are so many things to know about forts; many players probably do not know all of the following...

    For the moment, I have bolded the points I believe are lesser known or worth noting.




    } Forts provide +25% defensive bonus. This adds to any other defense modifiers on the tile. For example, a fort built on a hill forest has a +100% defense modifier (+25% from hill, +50% from forest, +25% from fort).

    } Forts can be built on top of any terrain or overlay (except oasis, strangely), but they cannot exist on a tile with another improvement simultaneously (except roads of course). A fort therefore does not remove a forest or jungle. Forts obviously can't be built on water, peaks or cities.

    } Forts require the tech Mathematics (not Construction) before your wokers can build them.

    } Forts require 10 worker turns to build (15 on epic, 38 turns on marathon, 7 turns on quick). Forts can only be built in your territory and in neutral (ie. outside all borders) territory - never in foreign territory.

    } City Garrison promotions are used by units defending forts.

    } City Raider promotions are used against units in forts. (hey it's only fair :))

    } Forts connect resources when they are in your borders and connected to the necessary roads/rivers. In terms of connecting up the resource forts are equivalent to the resource-specific tile improvement, but they do not provide the specific yield bonus for that tile.

    } Forts with roads function as nodes linking road-networks to coast-networks. This is especially useful for hooking up resources on small offshore islands which aren't worth an extra city. The fort itself can also be in neutral territory to establish the connection. These forts can also connect coastal trade networks which are split by impassable ice. (thanks DanF771)

    } Forts in home territory and neutral territory heal units at 20HP per turn, just as cities do. Normally units in home territory get 15HP per turn, and units in neutral territory get 10HP per turn.

    } Forts can be used as canals. Any fort in your culture boders, or city, which touches a water tile (inland lake or coast) can have naval units pass through it. Forts in neutral territory can not be used as canals. For a civ that has open borders with you, their naval units cannot use your forts but they can use your cities.
    Additional note: Masters can always use a vassal's fort canals, but vassals can only use the master's fort canals when they have open borders. Strangely, your privateers cannot be attacked by your vassals if they are in your forts, as it seems the vassal cannot see the privateers. (thanks DanF5771)
    Another note, by way of example, quoted from UncleJJ (thanks): "I've built a line of forts 8 wide across the southern end of my continent when it was blocked by ice flows. Submarines could get through and my workers had nothing better to do so I built this "Sothern Passage". Each fort had to be either next to water or next to ice (which counts as water for this purpose) and also needs to be inside your own culture for the ships to pass. This was quite useful, in that game, for shifting ships from one side of my continent to the other, and massing my fleets, rather than a long trip around the other continent as mine was blocked at the northern and southern ends."

    } Up to four air units can be based in a fort.

    } Paratroopers can paradrop from forts in friendly territory. Friendly territory only includes your territory and master/vassal territory. (thanks DanF5771)

    } If a naval or air unit is on a tile when it becomes occupied by an enemy land unit the naval or air unit is destroyed, so be careful!

    } Tactical nukes and cruise missiles can be rebased to forts, and launched from forts. They can also be loaded onto Submarines and Missile Cruisers from forts (the ship must be on the same tile - not an adjacent tile!). Missiles are also destroyed if an enemy land unit takes the fort.

    } Units with no movement points left can be loaded onto ships from forts (just like cities). Missiles can be rebased to forts and loaded on the same turn too.

    } Forts in enemy territory do not provide any benefit to you, not even the +25% defense bonus. To you, the enemy fort may as well not exist unless the enemy is using it! Equally, forts in your territory cannot be used by your enemies. Obviously, a fort in neutral territory benefits whoever controls it.

    } Siege units in forts cannot be flanked by mounted units with Flanking. In this sense, forts behave like cities, acting as safer places for you to store your siege units.

    } Units that have inherent defense bonuses for cities (eg. archers and longbows) use these bonuses in forts too.

    } The +25% defensive bonus of forts cannot be bombarded. At times this can make them easier to defend than a city!

    } Forts can be destroyed by spies. All improvements cost the same EPs when sabotaged with a spy. (thanks DanF5771)

    } Forts can be destroyed by units running the Air Bomb mission (available to Bombers, Stealth Bombers and Guided Missiles). Forts come with iAirBombDefense = 20 (like forest preserves; mines, quarries, wells and offshore platforms have 10; all others 5). (thanks Tephros and DanF5771)

    } If a fort is destroyed (eg. you could pillage your own fort or an enemy air unit might bomb it), air units are transferred to the nearest city or fort in your borders that has space available. If there is no space anywhere the air units are destroyed! Naval units will be expelled to the water. (thanks Tephros). Missile units will also be transferred to the nearest city or fort in your borders (there is no stack limit on missiles).


    How can you use forts?
    Please reply to this thread if you know other uses for them. So far I have only included things which may not be thought of. Things like making a tile easier to defend are obvious at this stage, but ways you could use that advantage could be elaborated on, if you want to, and I will put your comments here.


    } Connecting up resources outside of city BFCs.

    } Creating canals for your ships to pass through. It can be a big time saver, allowing fewer ships to defend more area on both sides of the canal.

    } Since no other civ can put their naval units in your forts, you can use them as safe zones for privateers! The civs who have open borders with you can't touch them, so you can pick off the occasional caravel that comes into range etc.

    } Forts can be "prebuilt". What I mean by that is that if it takes 15 worker turns to build it, and you put in 14 worker turns, the fort is nearly built but you can leave a better improvement on the tile. For example if you have a happiness resource on a tile that could be used for a canal, and you only need that canal very occasionally, you could build that fort only when you need to use it and rebuild the improvement when you're not using it. This requires you to have the workers available to do it.
    Additional note (thanks Tephros): About the pre-building. Sometimes with spies or planes the enemy will try to destroy your strategic resource improvements. If this happens to be your only oil source, it can halt progress on important units. If you have an oil source within your big fat cross, build the well but then prebuild a fort so that if the well is destroyed you can immediately get a worker there and complete the prebuilt fort so that there is no lapse in access. For oil outside of a big fat cross, you can prebuild the well over the fort. In both cases, be careful not to actually complete the prebuild though. Also a good idea to keep a spy and interception-promoted SAM on those tiles.

    } Loading units onto transports, if you're ever in a situation where your units are having to stop on the tile adjacent to your ship, you could put a fort there and get an extra turn of movement with the ship.

    } Forts can be used to form canals 2 tiles wide. This is because each fort only needs to be touching 1 water tile. Technically you can form fort canals as long as you want but each fort must be touching a water tile. A fort chain may make a a canal 3 tiles wide, for example, if there is an inland lake touching the middle fort. (thanks Tephros)

    } If your air and naval units stationed in a fort are in serious danger, you can self-pillage the fort with one of your (last) land units to trigger an auto-rebase of those units to a safer place even when they have no movement points left. (thanks DanF5771)
     
    jmas and MAvL like this.
  2. Tephros

    Tephros Caffeine Junkie

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    Thanks. I did not know all of those facts.

    For canal use you should note that 2 forts together can form a canal, but beyond that will not work. Thus if you have a 2-tile thick land mass, you can create your own exclusive panama-style shortcut across the landmass. There are special cases where you can pass thicker areas, for example if there is a fresh water lake within 2 tiles of the ocean, and within 2 tiles of the other side.

    I'd also note that forts can be destroyed by spies and air units. The cost for spies seem to be comparable to other improvements that take the same number of turns to build. Air units, however, have a much harder time destroying forts than regular improvements and even bombers will usually fail several times before they destroy the fort.

    I do know that land units will stay put if the fort is destroyed. Air units are transferred to the nearest city or fort within your borders that has space available. If there is no space available anywhere, the air units are destroyed. Naval units are expelled to the water.

    About the pre-building. Sometimes with spies or planes the enemy will try to destroy your strategic resource improvements. If this happens to be your only oil source, it can halt progress on important units. If you have an oil source within your big fat cross, build the well but then prebuild a fort so that if the well is destroyed you can immediately get a worker there and complete the prebuilt fort so that there is no lapse in access. For oil outside of a big fat cross, you can prebuild the well over the fort. In both cases, be careful not to actually complete the prebuild though. Also a good idea to keep a spy and interception-promoted SAM on those tiles.
     
  3. DanF5771

    DanF5771 Emperor

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    Forts are great, this article was long overdue. Here are some more interesting points and suggestions for minor corrections.
    Forts cannot be built on top of an oasis or in any foreign territory (the term "enemy" might be misleading).
    Forts with roads function as nodes linking road-networks to coast-networks. This is especially useful for hooking up resources on small offshore islands which aren't worth an extra city. The fort itself can also be in neutral territory to establish the connection. These forts can also connect coastal trade networks which are split by impassable ice.
    2 special functions are only provided by forts in FRIENDLY territory -- important! - this not only includes your home territory, but also the territory of your vassals.
    The one function not mentioned yet is, Paratroopers can paradrop from these forts. The other function is the canal-function! Yes, your vassal can use your forts as canals (with open borders) and you can use your vassal's forts (always). But your Privateers are not in danger, since a vassal doesn't attack them in his Master's forts (I'm not entirely sure why not, they don't seem to see them).

    If your air and naval units stationed in a fort are in serious danger, you can self-pillage the fort with one of your (last) land units to trigger an auto-rebase of those units to a safer place even when they have no movement points left.

    As Tephros already mentioned forts come with iAirBombDefense = 20 (like forest preserves; mines, quarries, wells and offshore platforms have 10; all others 5).
    All improvements cost the same EPs when sabotaged with a spy.
     
  4. PieceOfMind

    PieceOfMind Drill IV Defender Retired Moderator

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    Both posts full of excellent points. Thank you! I'll make the additions/corrections shortly.

    Just a follow up question DanF, can vassals use their master's forts for paradrops?
     
  5. Tephros

    Tephros Caffeine Junkie

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    So if you build a fort on a resource in neutral territory, ownership is defined by a military unit occupying the fort? How exactly does that work? Is it the last military unit to enter the empty fort? Or am I misunderstanding you completely?
     
  6. PieceOfMind

    PieceOfMind Drill IV Defender Retired Moderator

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    I'd suspect it's effectively a port that anyone can use if they have a network connected to it. Obviously if an enemy unit is on it, it will block any routes through it, including the use of it as a port. It shouldn't matter who was on it last. I am just guessing though.

    In terms of connecting resources, resource access is only provided if the resource is in your borders. The fort itself just provides a link to the coast network. See this picture...

    The city has access to the copper but not the iron. It is hard to see but there is a road connecting the mine and fort.

    Spoiler :
     

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  7. DanF5771

    DanF5771 Emperor

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    Yes, vassals can paradrop from the master's forts too. (You can test these things in WB by making yourself the vassal of an AI, it's interesting).

    Your explanations re forts and the resource availability are correct, but enemy units in a home or neutral fort do not negate it's port function.

    Here is another example to demonstrate the benefits of the usage as a port to connect coastal networks which are otherwise split by ice. I can build Knights in Istanbul by getting Horses and Iron from the islands with a coastal pre-Astro network.

    Spoiler :
     
  8. Indiansmoke

    Indiansmoke Deity

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    Another point is that if you have a rsource that is on an island (like copper and iron in example) and is within cultural borders but outside BFC then you need fort and road to connect it. For some reason mine or relative iomprovement will not do the trick
     
  9. PieceOfMind

    PieceOfMind Drill IV Defender Retired Moderator

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    That's a neat example. Thanks for sharing it!

    So enemy units on the fort will not negate its port function, but they do normally block road routes don't they? It seems counter intuitive that the a fort can still act as a route connecting two coastal networks if an enemy occupies the fort.
     
  10. DanF5771

    DanF5771 Emperor

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    I don't think enemy units have any effect on your trade networks unless it's a naval unit which performs the blockade mission. E.g. an enemy unit standing on your intact road-connected Copper mine in your BFC will not negate your access to Copper. If anybody has a save proving the opposite, I'd be interested...
     
  11. PieceOfMind

    PieceOfMind Drill IV Defender Retired Moderator

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    No, you're right I just checked with WB while you were answering. :)

    I just always kind of assumed it. In that case, what I called counter-intuitive a moment ago, I now no longer consider counter-intuitive but intuitive. :D
     
  12. DanF5771

    DanF5771 Emperor

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    ^Yeah the whole trade network / trade routes / plotgroups system is pretty complex and sometimes irritating and counter-intuitive. As I learned recently it is also suffering from a minor bug ... :rolleyes: ;).

    Indiansmoke: IMO you ALWAYS need some sort of port (either an extra city or a fort) to connect resources located on separate islands, be they in another city's BFC or not.

    Edit: Disclaimer - all my findings are for BTS 3.17 (don't know if things worked differently in previous versions...).
     
  13. Tephros

    Tephros Caffeine Junkie

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    I know the point of this thread isn't to say what forts should do, but I can't resist. I really think units attacking from forts should get a 10% strength bonus so that forts matter tactically aside from the fact that the AI attacks them as if they're cities. Whenever forts come up I keep thinking about that. In real life forts are more than just a difficult thing to attack.
     
  14. PieceOfMind

    PieceOfMind Drill IV Defender Retired Moderator

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    Yeah that bug and the post you made explaining it made my head hurt a bit, mainly concerning the way the bug shows itself. I get the impression though the bug is minor in the sense that the situations in which it occurs are very infrequent, and when they do occur the consequences are not game-breaking, or even all that serious.

    I would be confident in saying this is a true bug (I hope Dresden isn't disagreeing with you.. why would he?), and no amount of QA testing by Firaxis would have revealed this. Truly it's one of the most well hidden bugs of BtS. :)
     
  15. DanF5771

    DanF5771 Emperor

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    Right, that's why I added the ;) to the above :rolleyes:.
     
  16. neckface

    neckface Warlord

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    Do forts gain the additional defensive multiplier when they are build on forest / jungles?
    i.e. +25% bonus for fort AND +50% bonus for forest??
     
  17. PieceOfMind

    PieceOfMind Drill IV Defender Retired Moderator

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    Absolutely!

    That is why they are often easier to defend than a city.
     
  18. r_rolo1

    r_rolo1 King of myself

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    Lucky me :rolleyes:

    Well, there is another "bug" with trade networks regarding forts , that my SGOTM team stumbled on ( that is why I don't link it, given that is a ongoing game ): if you make the road in the tile you're planning to use a fort as a port and then the fort, the trade route will only link the road to the port function of the fort after another change elsewhere force the recalculation of the trade network. Making fort then road works ok.

    P.S II : for the ppl that want to test it, there are some WBed test saves in the below refered thread that can be used to that. Not obviously the HoF save :p

    DanF, Smurkz team, post 589 ;)

    P.S BTW, forts deny B. phant special ability like cities, right? ;)
     

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  19. r_rolo1

    r_rolo1 King of myself

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    You forgot +25% if on a hill ;) Forts in forested/jungled hills are VERY dificult to take down by frontal attack
     
  20. DanF5771

    DanF5771 Emperor

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    rolo: Too bad for team Smurkz! This fort-after-road-problem was fixed in Dresden's unofficial patch 0.21.
     

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