40d:Defense guide

In Dwarf Fortress, you will often find yourself beset by hostile creatures looking to murder your Dwarves and take their things. Protecting your fortress from intruders is a challenging task and a complex topic. A wide variety of creatures can threaten your dwarves, and there is no one approach or philosophy that perfectly addresses them all. Fortress layout, military organization and training, traps, and more all contribute to the overall "defense" and survivability of your fortress and the dwarves that live and work there and in the world around it, and likewise no one article can include every last detail. This guide will pull from many other articles, but will prefer to refer to those rather than re-post information that is already found (and better placed) there.

There are three important things to consider when planning the defenses for your fortress. First, you must protect the fortress itself - the buildings, the hallways, the dwarves within it. But second, protecting the dwarves outside and topside as they go about their work is also important. These two goals can often be rather divergent, as your dwarves may need to wander the open countryside to collect herbs, cut trees, hunt, fish, or otherwise just enjoy nature, and while outside your the bounds of your fortress can be quite vulnerable. Lastly (and leastly), is game style - you want the game to be "fun" for you, and with some situations it's quite possible to defend yourself into complete boredom, or just go down a road that is not attractive style-wise. While this article cannot tell you how to have fun, it will comment on that last when appropriate, and you should keep it in mind as well.

Note - There is not room in this article to expand adequately on every sub-topic - please see specific articles for a complete discussion as desired.

General Guidelines

While admitting that "Rules are made to be broken", there are some general recommendations that have a proven value in defending a fortress:

• Minimize fortress entrances: Have a strong and clear distinction between inside and outside. This usually corresponds to underground and surface, but not always - you can have a complete medieval-style castle complex on the surface. But each point of entry should be hardened against attack. Don't make more entrances than really necessary. If there is a useless or redundant opening, seal it off, one way or another. (Some creatures can destroy doors and drawbridges if they can reach them.)

• Concentric circles: Think redundancy - one wall may not be enough. With the existence of door-destroying and bow-wielding attackers, double or multiple hard barriers between the inside and the outside is essential to fend off the worst assaults, and if they get inside one barrier it's nice to have another behind that. Sometimes captives will escape their cages inside your fortress. The choke points between the circles are where you build traps and doors, and station troops.

• Assume the worst: Build up your defenses before the enemy shows up - like right now! Plan on being sieged by scores of goblin archers, door-breaking trolls, invisible kobold master thieves, dive-bombing giant eagles, flame-breathing fire imps, angry elephants, and a bronze colossus - all at once. Hopefully, you will never have to face that kind of threat, but being ready for anything is the best bet, and, more realistically, when things go wrong (and with dwarfs, they will, just believe it) you will have a buffer of defense to fall back on.

Threats

• Wild animals

Some animals are quite dangerous, but most are easily excluded by the humble door or hatch, even if it's not forbidden. Some few are able to destroy doors and hatches, statues and other buildings. Creature vary in threat and habits. Some animals are thieves (see below), or eat your food (like bears. Combat is random, and any animal can kill any dwarf - and vice versa.

Wild animals can appear from the topside, but also from an underground river or pool that you find by mining into it. In an evil or wild biome, the creatures can be much tougher and more aggressive.

• Thieves & child snatchers

Many creatures are "thieves" in the general sense - tribes of rhesus macaques or raccoons offer their own potential headaches, grabbing items of value and running. But a creature with a career title of Thief has a few additional nasty surprises, namely being invisible until spotted by your dwarves or domestic animals, being able to bypass locked or forbidden doors, and some imperfect ability to avoid triggering traps, though some are better at it than others. Kobolds and goblins are individually more dangerous than animals, but when spotted there's an alert message, either "Protect the hoard!" or "Protect the children!", as appropriate.

• Ambushes

An ambush is a small number of enemies (less than ten) that are invisible until spotted, but are easier to spot than thieves. The alert message is "An ambush! Curse them!" They skulk around the outside of your fortress, looking for wandering dwarves or caravans entering or leaving.

• Siege

A siege is a large number of armed and organized attackers that are announced as soon as they appear on the map. The alert message is "A vile force of darkness has arrived!" While siegers are on the map, the word "SIEGE" appears in the top corners of the screen. Siegers are organized into a number of squads, each squad having a different weapon choice. Some sieges bring creatures with the armed attackers. If you are at war with a civilization, expect annual sieges at least.

• Enemy archers

Attackers with bows or crossbows are worth separate mention as they are much, much more threatening than those with melee weapons. Out-shooting them with your marksdwarves is risky, and charging them with melee fighters is even worse. Special techniques are needed to shield your dwarves from the deadly rain of arrows.

• Building destroyers

Some creatures have BUILDINGDESTROYER tag in their data file. This gives them the fearful capacity of tearing apart your doors and bridges and anything else that is built with the b + C keys. (This does not include walls.)

• Flying animals

Currently, without modding, the only flying creatures are wild animals, like the giant eagle. Be aware.

• Megabeasts

A megabeast is a particularly powerful and dangerous creature, such as a dragon or titan. Meagabeasts appear alone, with an alert message that mentions the beast by name. They often have unique characteristics which present unusual challenges, but are universally dangerous.

Elements of a defense

Dwarf Fortress is very open-ended, any number of defensive, engineering, fortification and military principles will work in DF that would have worked in the real Middle Ages. Combine different elements into the defense you want.

A Moat with a drawbridge is perhaps the simplest defense known to Dwarvenkind, and not a bad start. The Fortifications article on Wikipedia is also a good resource. But simply shutting the outside world out and allowing invaders to mill about outside your moat is not always a desirable solution. Enemies will still prevent traders from arriving, and prevent any desired outdoor activities. In addition, Dwarf Fortress players often find it enjoyable to perpetrate mass slaughter of invaders rather than glare at them from inside their caves.

For this, you will need a more complicated defense than a passive ditch and walls. One common method of defense is to build a walled tower above the entrance to your fortress, stationing Marksdwarves on the second floor overlooking the drawbridge-entrance. Another is to engineer a very long but narrow entrance, at the end of which are ballistae waiting to unload at unfortunate monsters in the field of fire. The variations are infinite.

Physical Layout

These are the walls, floor, fortifications and so on that create the towers and perimeters of your fortress, acting as physical barriers for your dwarves and against threats. However, they always work in conjunction with the other elements. Creative use of layouts can achieve some quite satisfying results.

Walls

Constructing walls around your entrance is the simplest start, and an essential part of fortress defense, but a wall alone is not a complete defense. Currently, no creature can knock down a wall. Not only does it keep enemies out, your archers can stand on top of the wall and fire down. Keep in mind that this makes them vulnerable to enemy fire. To protect against that, build fortifications.

Doors and hatches are the most obvious way to keep any enemy out. Door can only be double-wide - not enough to seal up an entrance for a wagon. You can forbid doors to keep humanoid enemies out, and your dwarves in. Outer doors can be closed against animals, to keep beloved pets from wandering into enemy fire. A floor hatch is just a vertical door.

Floodgates, alone or in a line, may be used as removable walls, since they need no support and disappear when "opened" remotely, although using a wide drawbridge will be much more economical in terms of Mechanisms. (Be aware that Megabeasts can batter down both raised floodgates and drawbridges, and any object can prevent a floodgate from closing again, even a single, stray crossbow bolt or confused animal.)

Remote control barriers

If you link a lever to a door, hatch cover or floodgate, it becomes impossible for your dwarves to open and close it normally. Pulling the lever is the only way to open it. This keeps your dwarves locked in as well as keeping enemies out. (It's unknown if thieves can bypass a door once it's linked.)

A floodgate can be used just like a door, with two differences: A floodgate can be placed next to another floodgate, unlike a door, which needs to be adjacent to a wall. A floodgate is closed by default, and can only be opened with a lever. Be careful not to trap your dwarves.

As mentioned, a drawbridge works as a door when "raised", sealing the passage it raises against.

You can use automate a door by using a pressure plate instead of a lever, but there are many complications there.

Moats and bridges

A retractable/raise-able bridge over a deep trench is an almost airtight defense - only flying creatures can pass it. The moat keeps building-destroyers away from the bridge, and the raised bridge blocks arrow fire. Channels may be used to form ditches, or moats. For defensive purposes they do not need to be filled with anything - as in the middle ages, a dry ditch is more than enough to prevent ground units from approaching (though of course, projectiles may be launched over it with impunity). With a retracting Bridge over the moat, any units or items on top of the bridge will be dropped into the moat (and, if the moat is filled with water, drown unless they can swim out; if it is filled with magma, they burn to death.)

The moat doesn't have to be filled with water or magma. Arguably, a dry moat is a better defense. If you want to build an access/escape route for your moat, consider where it leads - the enemy might use that too.

A moat with a non-retractable bridge is still potentially useful: It keeps enemy archers away from your fortifications, and it channels enemies into a narrow area. A drawbridge without a moat is just a big remote control door. This doesn't work with retracting bridges!

Drawbridges can throw creatures a distance (in a random direction) when the bridge is raised, possibly injuring them on landing. Creatures on top of drawbridges will be utterly destroyed if they are flush against wall and have a floor tile above them, as will anything, friend, foe or object, on a floor that is covered when the drawbridge is lowered. This offensive use of drawbridges is known as the Dwarven Atom Smasher.

There are three important things to remember: 1) Always build the bridge to raise towards the inside (so it cannot be destroyed when raised), 2) the lever has to be pulled by a civilian, not a soldier, and 3) water can freeze solid in cold weather. Also, some rare creatures can cross fluids, even magma. Nothing can climb the walls of a channel.

Fortifications

Fortifications are the marksdwarf's friend. They allow hand-held missile weapons to pass through. Projectiles have a chance of being blocked, based on the firer's skill and distance to the fortification. There's no miss chance if the firer is adjacent to the fortification. Keep your marksdwarves close and keep enemies away. Build fortified firing platforms above ground level and put a nice wide moat between the wall and the enemy. Fortifications have no effect on siege engines.

Like Fortifications, Vertical Bars and Wall Grates will also allow projectiles to fire through them while impeding units' movement. Unlike Fortifications, Bars and Grates may be connected to a Lever, and opened or closed remotely - thus, they are good for forming portcullis. These constructions provide no defense - the missile fire works both ways equally.

Military

A trained, armed, and armored military is the only way to bring the fight to the enemy. Building defenses to keep them safe is easy - keeping them in position is the tricky part. See Military design for different options.

Traps

The most reliable way to stop intruders is lots of traps. A line of traps can wipe out an ambushes entirely, and inflict a lot of damage on a siege. A thief's trap avoidance is subject to chance, so the more the better. However, vast numbers of traps have the potential to take some of the fun out of the game.

There are several types of traps that a mechanic can place in a single tile and that target a single creature, but there are larger, more complex traps that only you can design, using levers or pressure plates. (See Trap design.

Animals

Any animal (or dwarf) can act as a sentry. Most animals aren't strong enough to take more than one armoured goblin warrior, and enemies with bows are even worse. The real purpose of guard animals is to spot thieves. Anything will do here, even a kitten will do the job, and some players prefer not to use a useful animal. (Note - Some tamed animals will not fight goblins!)

Guard animals are a good second line of defense in open entrances after your traps. A wardog can usually tear a thief apart, and will delay goblin warriors while you respond. Also, the death of any animal will be announced, alerting you to the threat if you were not already aware of it.

Most enemies will go after your animals just as blindly as they attack your dwarves. An expendable chained animal can bait enemies into dangerous passages, even into places unconnected to your fortress.

Restraining animals in narrow corridors (width 1 or 2), or in matched pairs against the walls of 3-wide corridors, in places where enemy archers can't fire at them.

Siege engines

Siege engines take some planning to use effectively. Both catapults and ballistae can be very deadly, but both have their drawbacks. The most important factors are 1) that, unlike crossbows, both can only fire at targets on the same [z-level]], and 2) that they are manned by civilians who will flee if any enemy gets too close. (See siege weapon for full information and suggestions.)

Considerations

Now you know what you might face, and what cards you have in your hand. To that we add complications...

Surface jobs

There are many times when dwarfs want to work on the surface. Wood cutting, gathering plants, hunting, fishing, mining exposed veins or gems, building defenses,growing above-ground crops, helping wounded comrades or recovering dropped items are only the most likely. Often they are alone and vulnerable to wild beasts or ambushes.

You can try to wall in huge areas of the map, possibly with drawbridge gates that can open for Caravans, but the larger the area the vaster the project, the further your dwarves will be from existing defenses, and another example of dwarves working above ground.

Making smaller enclosures in key areas with underground tunnels leading to them can be easier as a first step. Likewise, tunneling to the inside of an exposed vein of ore keeps your miners sealed from the outside until you are prepared to mine the last tiles, possibly after placing doors or walls just inside that tunnel.

Having military stationed or patrolling nearby is another option.

Water sources

Access to water can be vital. Wounded dwarves need water, so if there's not an underground water source you'll lose valuable soldiers to thirst. Try to have a well or cistern your dwarves can use safely. Remember to keep an extra bucket or two available.

Some water sources are good locations for fishing, providing food during longer sieges.

Civilians stay underground

This setting, in the orders and options menu is the easiest way to keep your non-military dwarves out of sight of the enemy. It is far from perfect, as dwarves will do the "entrance dance." They will attempt to leave the fortress, and only cancel jobs once they reach the surface, as defined by the first "above ground" tiles they hit. Having entries with a "skylight" before the actual exit can solve this - and building walls around the skylight prevents archers from shooting down into it. Doesn't protect against flying creatures, though.

It takes a truly airtight fortress to turn this setting off while there are still enemies outside. It's only safe to turn this setting off once the drawbridges and such have sealed off your fortress entirely. If there's even one exit, your dwarves will use it. Try testing this while it's safe: Raise the bridges, just like you would in a siege, and designate some trees for cutting. If there's a way out, your woodcutters will find it.

• Screen the entrance. Build a simple wall around your entryway. This will keep your dwarves safe from enemy fire while doing the entrance dance.

• Seal the entrance. Prevents the entry dance, but also blocks your soldiers, which can trap them underground.

• Forbid dropped equipment and corpses. Mark every item on the battlefield as forbidden. This includes any items dropped by dead merchants or scuttled wagons. You can have this done automatically for dwarf and enemy corpses and inventories in the orders o menu at the forbid options F.

• Delete stockpiles and turn off tombs. As a preemptive measure, you can easily delete your Graveyard stockpiles. Dwarves don't haul things if there's no stockpile to place them in. Turning off or removing coffins stops burials as well.

• Keep them busy. Make a bunch of busy-work for your dwarves, just to keep them underground. It's not perfect but it helps. Time to re-organize your stockpiles.

Civilians trapped outdoors

Anything that blocks intruders will also block your dwarves. This can cause the problem of dwarves being trapped outside with the enemy, and the enemy will find them. Having more than one entrance can be useful here, but each requires adequate defenses - the weakest link and all that. If you make these entrances accessible by drawbridge only, with a (short) moat outside that, and keep the drawbridge up most of the time, having lots of entrances shouldn't be too much of a problem.

Trade depot & caravans

Factoring in a 3-tile wide access to the trade depot adds a layer of complexity. Letting merchants in while keeping enemies out requires a careful balance. The merchants can reveal ambushes and thieves like any other creature, and they can arrive in the middle of a siege. If they do, they can be slaughtered before reaching your doors, and that hurts you, (as well as possibly causing your civilian dwarfs to want to go running out and collect their dropped items.) Consider sending heavily armoured escorts when expecting a caravan.

Only wagons need a three tile wide path to the depot, so the elves and some of the dwarven and human merchants can still get through if it's only 1-tile wide. You will possibly want to build the depot underground, so civilian dwarves can access the depot and goods. Wagons can't use stairs, so you need a three-tile ramp, unless you can dig into the face of a cliff.

Branching corridors

Enemies will take the most direct path to your fortress, (even if it's not very direct at all). You can use this to your advantage. Have two paths to the fortress: a long, twisting, three-wide road, and a shorter, one tile wide, trap-filled passage. Attackers will usually prefer the short and deadly path. This makes a good line of fire for a ballista, too.

Alternately, you can have a primary, convenient, direct 3-wide path to your fortress open most of the time, with a convoluted detour that is forced (by drawbridges) only during sieges, lined with traps and overseen by marksdwarves. The possibilities are infinite.

Levers

Be careful where you place the levers controlling your various entrances, traps and other defenses. Or any lever at all, for that matter. Make sure they are either central or close to locations of idle dwarfs, or both. Near a meeting zone or bedrooms of nobles is often a good plan. Make sure that the entire path to each lever is underground or your dwarves might be unable to reach them if told to "stay underground". You can test this during peacetime, too. Try putting all your defense-related levers in a single room, and put a door on the entrance. Then you can lock your lever-puller inside to ensure rapid response time.

Another solution to the problem of rapid response time is to make your lever room double as a pump room. Pumping is a good way to build up your dwarves' attributes regardless of whether the pump is doing work or not. If you want a dedicated lever operator or three, turn off all their labors except pumping, and set the pumps up so that they can be operated exclusively by your dedicated lever operators. Rotate these positions every so often so the attribute gain will be distributed among multiple dwarves.

For the truly ambitious, the lever room could be spread over multiple levels, and the pumps could work together to power one or more artificial waterfalls. (Waterfalls work well in this case because their operation is not fortress-critical, and your dwarves like the mist they produce.)

Use Notes to label each lever and attached device and trap clearly - if you come back to a game after a week and can't remember your levers, they are useless (or, worse, dangerous!) Color code your levers with different color stone if that works for you.

AI abuse

Taking advantage of the game's Artificial Intelligence and pathfinding is a whole article in itself. Try leaving a door un-forbidden during an attack. When the bad guys approach the door, forbid it, and the enemy will wander off. Unlock it again, and they turn around and head back towards the door again. You can get enemies to march back and forth over a set of traps this way, or lure them deep into a complex trap. This could be automated via pressure plates. This might count as an exploit, or not - that's up to you, and what you consider fun and challenging.

General Suggestions

(work in progress 08:59, 2 June 2009 (UTC) )

For more specific suggestions, see also:

• Trap design (for specific suggestions, descriptions and blueprints for traps)
• Defense design (for specific suggestions, descriptions and blueprints for fortress layout)
• Military design (for specific suggestions and suggestions for organizing soldiers & military)