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.

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 opening, wall 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. 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.

• 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 high 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.

Military

The core of any defense plan is the soldiers. A trained, armed, and armored military is the only way to bring the fight to the enemy. Keeping them in position is the tricky part.

Roughing it

Always have your soldiers carry food. They will each need a backpack to carry it. This keeps your soldiers from wandering off to eat. You can also have them carry water in waterskins or flasks, but this isn't recommended for the long term, as it keeps your soldiers from drinking alcohol. For an around the clock guard, have them sleep on the ground while on duty. Hopefully the sounds of combat will wake them up before they get killed. Sleeping on the floor causes unhappy thoughts.

Daylight training room

Put a weapon rack on the surface near your entrance and make it a training room. Training dwarves will be in position if there's trouble. This also helps prevent cave adaption in your military. You can use an archery target this way, too.

Doors and hatches

The most obvious way to keep any enemy out is with a door. 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.

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.

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 stop a floodgate from closing again, even a single, stray crossbow bolt.)

Fortifications

Fortifications block movement and allow some missiles 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.

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, 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 swim, even in magma.

Remote control doors

If you link a lever to a door, 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 open 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.

A hatch cover can also be used this way.

As mentioned, a drawbridge works as a door

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

Traps

The most reliable way to stop intruders is lots of traps. A thief's trap avoidance is subject to chance. A line of traps can wipe out an ambushes entirely, and inflict a lot of damage on a siege.

Stone fall trap

This is the easiest trap to build, so you can easily build them in large numbers. Building lots of them is an easy way to earn experience for your mechanic, and add to your fort's defenses at the same time. Surround every intersection and stairway.

Cage trap

A very strong type of trap. Maybe even too strong. Currently, even a wooden or glass cage can hold indefinitely any creature, even trolls and megabeasts. Also, a cage trap never fails. A large creature can shrug off damage from a stone or weapon trap, but nothing can escape from a cage. Use cage traps as your outermost traps to catch the occasional wandering animal. A wounded elephant or unicorn in your front courtyard is not good at all.

Weapon trap

The gold standard of traps. This is the only simple trap that works repeatedly without reloading. They do get jammed, however. View the trap with the items in room t mode, and if there's a corpse inside the trap, it's jammed. None of the weapons on a jammed trap will function. It may be wiser to have several weapon traps with fewer weapons, rather than a smaller number of ten-weapon traps.

Using crossbows in weapon traps avoids the problem of jamming, but they must be kept loaded with ammo.

Guard animals

Chained animals are sentries, not fighters. Most animals aren't strong enough to take more than one goblin warrior. Enemies with bows are even worse. The real purpose of guard animals is to spot thieves. Anything will do here, a cat is fine too. Don't use something useful, like a war dog. Put animals in narrow corridors (width 1 or 2), in places where enemy archers can't see them.

Meeting hall as defense

You can use a meeting hall zone to attract animals to a given area. This makes a pretty poor defense in general, but in the very early game, it's a way to defend your wagon and stockpiles from thieving animals. Remove the zone later, or it attracts idle dwarves and children.

Bait animals

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.

Siege engines

Siege engines are not very useful in the current version. Catapults are only useful for training and stone disposal. Ballistas are deadly, but fire expensive ammunition, and hit both friend and foe alike.

Remember that siege operators are civilians. Fortunately, siege engines can fire through fortifications, just like normal projectiles.

Pillboxes and turrets

Build a tower specifically to post archers on. This lets you open fire before the enemy approaches your gates. A pillbox can be attached to your walls, or separate, so that the only access is from tunnels below. Carve fortifications on the second or third floor, so your dwarves can fire out. For extra usefulness, build a barracks, archery target, food stockpile, and dining room in or near the tower.

Siege engine turrets

If it's big enough, build a siege engine inside a pillbox. The device needs to be on ground level. Only a single tile of fortifications is needed to fire through the wall. You may want to build a moat or secondary wall to keep enemies at a distance. Position the tower to fire where invaders tend to congregate. Since siege operators are civilians, the "dwarves stay underground" order must be off.

Bridge Land Mines

Although this takes quite a few mechanisms and a lot of carpenters to pull of, you might be able to create a minefield on a bridge, create a very long moat and a bridge crossing it, make sure this bridge is not your outermost bridge, this bridge should be at least 20 squares long, but make sure it is no more than 4 squares wide. then set up a ton of pressure plates in a checkered pattern, build a floor above the bridge, and make supports next to the pressure plates, then remove the floor tiles not on the supports, destroy the up-stairs on to the floor, and link all your pressure plates to a support, as soon as a goblin walks on them, the floor caves in and makes an explosion knocking him and the friends he has near him off the bridge drowning them.

This should not be used as the only defense, make sure you have other traps at the ready in case of large sieges

NOTE: This is a very expensive creation and should only be used late in the game when you can spare lots of stone/wood/mechanisms. the bigger the bridge the more effective the trap

Considerations

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.

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 delete your 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.

Lever room

Be careful where you place the levers controlling your drawbridge. Or any lever at all, for that matter. Make sure that the entire path to each lever is underground or your dwarves might keep canceling the "pull lever" job. 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.)

Trade depot

Factoring in access to the trade depot adds a layer of complexity. Letting merchants in while keeping enemies out requires a careful balance. The merchants do reveal ambushes, and they can arrive in the middle of a siege.

Wagons need a three tile wide path to the depot. You will probably want to build the depot underground, so civilian dwarves can access the depot. Wagons can't use stairs, so you need a three-tile ramp, unless you can dig into the face of a cliff.

Airlock defenses/buffer zone

Build two walls, each with a drawbridge. Build the trade depot in the buffer zone between them. Keep the outer bridge open, and the inner one closed. When the merchants appear, put crossbows on the walls to guard their approach. Once all the merchants are safely inside, close the outer bridge. Once there's no enemies left in the buffer zone, open the inner bridge so your civilians can start loading up the depot.

The airlock pattern can be useful even without putting the depot there. Let a few siegers in at a time, and crush them. Reset the traps, Rest up the soldiers, and repeat.

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. Having more than one entrance can be useful here. If you make these entrances accessible by drawbridge only, and keep the drawbridge up most of the time, having lots of entrances shouldn't be too much of a problem.

Branching corridors

Enemies will take the most direct path to your fortress. 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.

This isn't a perfectly reliable method, but surprisingly effective.

AI abuse

Taking advantage of pathfinding AI is a whole guide 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. This might count as an exploit.

Roach motel

Build a long, narrow, and twisty passage, accessible from the outside, but unconnected to your fortress. Build as many traps as you like. Place a bait animal inside. Enemy attackers walk right in, and get torn apart by the traps. If any manage to make it to the end, and kill the useless animal, they're surrounded by traps, and no closer to your fortress.

If the roach motel is deep enough underground, you can build a tunnel above it, channel down, and mark the channel a pit/pond. That way, you can "reload" a new bait animal.

Water sources

Access to water can be important. 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.

Pathing slowdowns

If you're playing on a low-powered machine and you close up all entrances to your fortress during a siege, your game may grind to a halt and/or crash as the siegers continuously fail at pathfinding into your fortress. Bait animals may alleviate this.

Examples

3 Bridges

An example of some advanced defensive construction tactics to deal with vile forces of "any" size. (See picture).

• Bridge 1 seals off the entire base
• Bridge 2 forces everyone to take the long, winding, heavily trapped path of death.
• Bridge 3 seals the inside of the fortress

Clever triggering of the bridges allows you to break the hostile forces into smaller chunks to be trapped in the courtyard while being caught in traps and a crossfire of arrows from the fortifications around.