Defense structures

For strategies against threats, see Defense tactics.

Raids are frequent and numerous as they don't journey towards your base from their "camp" but just spawn on your map. Enemies don't worry about their base as much as players do. Because of this, additional measures need to be taken into account. This can make a significant difference in defensive strength against raiders, besides defeating them using clever tactics.

Basically, players have to fight the same enemy AI programming for each type of hostile but the approach to it may differ according to gameplay preferences, either face to face for a more combative experience, behind killboxes for a less threatening measure, or both combined.

Terrain features

Before laying blueprints, first inspect the natural features that can work as defenses, such as ancient structures, marshes, mountains and rivers.

Moats

Water or marsh tiles can be used as a moat which will greatly slow down the enemy's progression, giving you time to shoot them down. This is a way to make use of water tiles which obstruct the construction of a full wall by turning the water into a strategic location, such as a chokepoint.

Marsh used as moats to slow enemy advance, with little islands full of deadfall traps.

Mountains

For most map tiles, mountains can be incorporated into part of your defensive walls. You may also build a fortified panic room below the mountains for use during sieges or raids that are too hard to defeat.

In mountainous tiles you can choose to dig into the mountain, or find an area surrounded by mountains on 3 (or even 4) sides, then fortify with walls. Both make excellent defensive positions against most types of raiders (except sappers).

Early-game defense

At the very beginning your most primitive security are deadfall traps, sandbags and stone chunks. You will need to find a balance between these three so that there's enough materials available, hauling them won't be too much time consuming and of course, the terrain feature analysis to determine whether which type would be more efficient in your perimeter.

Assuming you already raised your first wall layer, it's very likely you had to move stone chunks either to build rooms, production structures or to open a growing zone, all the while you were gathering raw materials in a stockpile zone. As you move stone chunks to open space, you might as well use that action to create the Dumping stockpile zone on the outer side of your wall, covering its width and expanding it further three tiles away. This is very helpful mostly as a fire prevention. Although literally, you didn't built any defensive structure it still counts as a security measure, as the stone chunks will stop fire spree progression impeding natural fire from burning your wooden walls.

Performing this action can be time consuming, so for a short period work, instead of expanding three tiles away, just a single line covering your entire wall width would be a good start. Your speed in this matter will be greatly affected by the number of haulers available. It becomes incredibly fast if you can tame and train intelligent animals to do the hauling for you. Then you will be able to actually build defensive structures while the animals do this chunks line for you.

Perimeter walls

The most essential building to keep threats away, so long as the base is self sustainable inside. Many layers can be raised as you grow expansively, making the first the inner most and the latest the outermost. While the innermost may be faster to build with wood, the outermost layers can be made of stone. There's not much need to deconstruct walls in order to upgrade them, just refill them with better materials as their segments get destroyed by attacks, or demolish them if you run out of space.

Walls can make good use of surrounding hills/mountains by incorporating them to the wall and reduce both workload and materials. Marshes and water surfaces do not allow construction but can be taken advantage of as a moat.

Walls can be erected in multiple layers as well, which can deter sappers but is of course more demanding. Leave a 1-tile gap between the walls so repairmen can access each of the walls without having to go out.

Behind your walls, it is essential to have additional cover or defenses behind them, since a wall alone cannot defeat the enemy. When building lines of defenses, instead of putting the second layer right next to the first, consider leaving a gap between both so that your long-range shooters have enough distance to pick off targets long before they can be reached by melee hostiles.

Pay attention when expanding towards the edges of the map as there's a boundary only visible when "Structure" is selected but not before that.

Strategy

Enemies mostly use melee attacks even when firing point-blank would destroy it faster. Walls alone can effectively fend off early game stage raids if enough repairmen can keep the walls standing while enemies start to starve and become tired. Placing several doors separated by each other by 15 to 20 tiles allow multiple exits and also a tactical benefit to fire a same target from two or more sides when they spread out, killing them one by one.

When segments are broken through, they become chokepoints which allow your colonists to concentrate fire on. Hostiles will use your walls for cover, so make sure the inside is well-defended.

Walls are weak against explosives such as frag grenades. Grenadiers will continuously throw them, dealing heavy damage in a short time and sometimes killing their comrades who are bashing down the same spot. Target those with explosive weapons first to prevent breaches, and when your efforts are not enough, this shall signal the time to retreat backwards to your inner walls or any other defensive structure inside.

Walls are excellent structures to protect from Predator attacks and Manhunter packs, which don't target colonists safely behind them. However, if a colonist is seen passing through doors, they will attempt to break them down.

Cover management

Effective cover is an essential part in any defense, being able to negate a large part of any potential damage that can be dealt to your colonists. Enemies can also use cover to their advantage, so you should be careful of that as well.

Low cover do not seem to stack when placed in a double layer.

Cover emplacements

If you're short on materials, such as during the start, you won't need to surround the whole settlement with sandbags yet. Just have short walls of sandbags facing the enemy to block any incoming bullets. If you're even more desperate you can use stone chunks instead of sandbags.

You should put them near your base to make it harder for enemies to take advantage of them.

Perimeter sandbags

An essential defense in a base without killboxes (see below), perimeter walls or the like, this simply involves surrounding your base with sandbags. This provides great cover from gunfire, stopping 65% of the bullets that will otherwise hit your colonists. However this does not protect against explosive weapons.

Pros

• More flexible in terms of positioning
• More complete coverage

Cons

• No protection against explosives
• More expensive than partial coverage, especially in larger bases

Bunkers

Map ruins converted into a pillbox.

If you prefer prolonged firefights instead of taking your enemies out with cheap tricks, then this is for you. This is an early game strategy because all you need for it is walls. First, build a room in an area where you expect enemies to approach from, or convert one from the various ruins laying around. Simply build a structure in any shape and then deconstruct a few walls to make some holes -- these will be firing holes for your shooters, where they can use the walls as cover.

Additionally, build a roof for your bunker so that every cell is protected from bad weather like rain and lightning strikes. So, when a raider attack comes and your shooters head to the bunker, they now enjoy not only the full cover bonus from having thick walls between them and the enemy.

To truly finish the bunker, add flooring so your colonists don't have to worry so much about fires while inside.

Pros

• Cheap -- all it takes is whatever materials you use for the walls
• Simple, easy and fun to build -- just make a room and knock out holes for your shooters
• Makes it very hard for your enemies to hit your colonists since they are behind full cover
• You can easily extend this into a full bunker system just by adding more walls and knocking out more holes

Cons

• Should enemies overrun your bunker(s), they can turn the defenses on you to devastating effect
• May require Stonecutting research to get walls that are good enough to withstand sustained fire -- wood and steel just don't cut it

Pillboxes can be incorporated into perimeter walls, but make sure that there is no direct entry from there, such as by building a durable door.

Alternating sandbags

Alternating walls with sandbags can provide even better cover, is slightly cheaper (assuming use of Steel or cheaper materials) and has a chance of blocking explosives. However, depending on the material, the walls may be flammable and also have less health than the sandbags.

The "Fire Wall"

An effective cover design is to alternate 2 walls and 1 sand bag, by doing this you have 3 colonists shooting out of the same hole, 2 behind full cover and one behind low cover. This method can be expanded as long as there is room.

Example of advanced cover using walls.
Colonists behind walls are enjoying full cover, with 75% of shots blocked.
Colonists behind sandbags are at half cover, with 65% of shots blocked.

Pros

• Gives excellent cover
• Allows defenders to attack a wide range of targets while remaining behind cover
• Prevents colonists from ganging up on enemies
• Stops some explosives

Cons

• Narrows the attack area, so the attackers must come straight at the defenders

Cover removal

While sandbags already give you an advantage over raiders in terms of cover (65% vs 50%), removing all sources of cover near your base is still very useful when dealing with ranged enemies as they will then have nowhere to hide.

Haul all stone chunks towards a dump behind your defensive lines so enemies can't use them. Enemy snipers can shoot from up to 45 tiles away, though most raiders can't shoot that far, so removing chunks around 30 tiles away from your defenses can deprive most enemies of suitable cover.

Watch out for your crop fields as colonists tend to move and lay out chunks in straight lines, suitable for raiders to take cover behind.

Cover baiting

Once there's no suitable cover nearby, ranged attackers will scramble to find any suitable cover. You can exploit this by placing any form of low cover to attract them to a place where they can be dealt with more easily. Stools work good though you should expect them to wear out quite fast under constant fire.

If the cover is hard to remove (such as plants constantly regrowing in plant-rich biomes) you can manipulate stone chunks in ways that give them a disadvantage. For example, putting gaps between each chunk exposes the enemy behind to fire directed diagonally.

You can put traps behind the bait cover, which makes it slightly easier to trigger, though still less effective than chokepoints.

Chokepoints

Slowing tunnel in front of a wall, with alternated sandbags for maximum slowing efficiency and a twist to break line of sight. An additional sandbag is placed to discourage raiders from using walls as cover.

Chokepoints allow your colonists to concentrate firepower, killing incoming attackers effectively, as well as utilize traps to their maximum potential.

At its simplest, it involves the use of a single opening in a wall, coupled with a location for colonists or turrets to fire and beat them, sometimes with traps to catch some of the unaware attackers.

If the chokepoint is straight, remove all potential source of cover nearby, such as trees or rubble, so raiders can't shoot into the chokepoint. They can still use the walls of the choke as cover though.

A strategy is to litter the choke with sandbags or rubble, greatly slowing down the raiders and giving you time to deal with them. They also prevent raiders from standing on them, forcing them into your defenses.

You can concentrate fire on a crafting spot or animal sleeping spot placed right in the entrance with miniguns to rip incoming raiders apart.

Slowing tunnel

One early-mid game tactic to slow down your enemies is by (possibly using mountains to help) creating a narrow strip between your colony and potential areas where raiders could attack from, then alternating sandbags or debris with unoccupied space, close to the exit of the strip (the end closer to your colony obviously).

To stop them from using the chunks or sandbags to their advantage, build a turn to break their line of sight.

Don't put sandbags or chunks right next to each other, otherwise they will simply vault over multiple bags at once, reducing their slowing efficiency. An excessively long tunnel also prompts them to break in instead of entering through it.

Pros

• Fairly cheap
• Easy to build

Cons

• Does not deal damage on its own
• Short slowing time

Traps

Understanding A.I.

Friendly AI will always prefer to move through doors and avoid traps, while enemies will prefer to go around structures by entering open spaces and are unable to see traps.

Because of that, trap chokepoints like this one are effective. Enemies will prefer to use the corridors rather than attempting to destroy doors as it would be more time consuming, and being unable to see the traps, they will trip them hopelessly. While your colonists can safely take refuge using the door instead. Enemies cannot open doors unless they destroy them first.

Trap memory

Hostile factions can remember the tile location of your traps for a single quadrum, so long as any survivor manages to tell the tale by escaping the map. Factions keep this information to themselves and do not share with others. This is of course, once a trap has been triggered by someone walking over it only, causing them to attempt to avoid the tile in future attacks.

They will still walk over known trapped tiles in order to get to you, if there are no other routes available.

Deadfall traps

The only initially available defense that deals damage. Deals single-target damage, can be rearmed, and needs careful attention on it's placement. They should be placed in areas where enemies are expected to come by, but also leaving free areas so that your colonists and friendlies can pass harmlessly or else they would be seen as walls too (a good example is a checkerboard pattern).

Traps made of wood are highly flammable so its best to place them on rock or soil, far from grass or trees, while stone traps don't get burnt. All kinds of traps can be destroyed by explosions so they shouldn't be placed right in front of your walls as grenadiers are most likely to throw grenades to breach your walls while at the same time destroying your deadfall traps altogether. It is easy to determine where enemies will walk over by analyzing the terrain walk speed feature, as AI pathing will prefer ground where the speed is 100% or the highest on the intended course.

Trap chokepoints

As mentioned above, you can lay traps in chokepoints to greatly increase the chances of the enemy triggering them.

Pros:

• Passive defense as it doesn't require your immediate intervention.
• Multi-use as traps can be rearmed, making this method economical in the long run.
• Can be expanded as needed.

Cons

• High resource cost, unfeasible in resource poor maps.
• Cannot halt large crowds or shielded enemies.
• Cannot delay enemies very long.

Roof trap

This clever trap is simple to set up and hard-hitting when triggered. It can be considered a giant single-use deadfall trap.

All you need to do is to erect 1 pillar made of a low-HP material, optimally wood, then build a roof over it. When raiders walk near the pillar, demolish it from a distance with a few long-range guns (or grenades if you're reckless). You can remove the home area near the pillar to prevent colonists from repairing it, then damage it until it can be destroyed in 1 hit.

After the pillar is destroyed, the roof will fall, crushing the raiders on the head, neck or torso and dealing up to 20 damage (though armor will negate part of it).

You can even put down some form of low cover such as stools to bait the enemy into going under the roof trap for 'cover'.
Triggering an IED trap near it is also very effective, with the advantage of being automatically triggered and dealing even more damage with its explosion.

This is technically more of a clever use of game mechanics than an actual trap, so raiders won't detect it, nor will they treat it as a trap.

Pros

• Large radius; easily injures a sizable group of raiders at once
• Penetrates shields
• Low cost; only 5 wood each for a single use
• No risk of friendly activation
• Undetectable by raiders, and position will not be remembered

Cons

• Hard to trigger; you may need to lead your targets
• Low damage
• Rarely kills or incapacitates
• Cannot be used with killboxes easily

It is optimal for softening a group of raiders so it's easier to defeat them.

• 

  Roof trap before triggering.

• 

  Roof trap after triggering, having injured some raiders (some through shields) and left a large pile of rubble.

• 

  More refined roof trap design with stools to lure the enemy into using them as cover, along with an IED trap to automatically trigger the trap. Significantly more expensive.

Damage minimization

These are ways to minimize damage done to your base.

Walled geothermal generator. The extra space allows heat to escape without being trapped inside. Note that the entire setup is unroofed.

Firebreaks

4-tile wide strips of metal or stone tiles is capable of stopping the spread of fires. This can negate many fires from reaching your base and burning it down.

You can build one surrounding your base, and divide the map into sections in order to control fires.

Keep in mind that building such amounts of floors usually requires huge amounts of building materials.

Walling structures

You should build an additional wall around your important structures, such as generators, power conduits or cash crops, even if you do have a perimeter wall in place. This causes raiders to prioritize other targets over these, averting destruction.

For geothermal generators, remember to have some exposed roof areas so the heat from the generator can vent out instead of being trapped inside.

Power network

It's not a good idea to have only 1 wire connect everything in your base, as 1 broken-down conduit can easily cause a blackout.

Instead, build a network of conduits to make sure that the power network stays on even with multiple breaks.

Panic room

4-man panic room built inside a mountain.

You can dig out a panic room deep into the mountains. This provides a good escape if you know that you can't defeat an incoming group of raiders, or you are losing and need retreat, provided you manage to get to the room in time.
Building one out of walls is also an option, and you don't need to build as many layers of walls, since they will attack the walls as well, rather than just the doors, and it also allows more flexible pisitioning of the room. However, you lose the advantage of immunity against mortar shells and innate temperature control.

You don't need to make the panic room big enough to accommodate the whole colony, as the point of a panic room is to preserve colonists in a dire situation so you can rebuild later on. Choose the colonists most important to you when it's time to escape to these rooms.

A panic room need the following:

• At least 4 layers of durable doors or walls to successfully block off raiders (and you may need more during mid-lategame)
• Enough food to last 1-2 days at full capacity
• Medicine for the wounded, for injury is likely during the retreat
• Joy objects (otherwise colonists may face a huge -20 mood penalty)

If you want, you can put beds and tables to make sure your colonists don't feel too bad while cooped up inside. You can also choose to put building materials to seal up the entrance with cheaper and more durable walls. Putting resources inside also helps with rebuilding, though they take up space.

While inside the panic room, if you're down on your last door or layer of wall, assign your best builder to hold the door by repairing it, and make sure the others don't go out. Disabling firefighting for covering colonists or restricting them to the panic room can help stop them from leaving.

Consider building multiple panic rooms so your colonists have another panic room within reach if a raid blocks off access to one.

Mid-late game defense

Turrets

With the low firepower and high power usage of the improvised turret in vanilla, it is not a good idea to extensively rely on them, especially in mid-late game. However they do provide decent additional fire to lay on the enemy combining with gunners, and also serve as a distraction from your more valuable colonists.

Turret-reliant perimeter defenses are generally only viable for the first several raids, after which the areas will quickly get overwhelmed each raid due to not being able to focus fire on the numerous raiders.

While protecting the outside starting area, you may want to rapidly pause the game during raids and give orders to repair damaged turrets.

Remember that raiders will run from exploding turrets, and to get your colonists to run from them as well.

Turret emplacements

Turrets should each get their own sandbags to reduce incoming fire both to the turret and colonists behind the turret repairing/shooting. This has the added advantage of making it harder for raiders to run from an exploding turret.

They should be spaced out to prevent a turret explosion from damaging other turrets, potentially causing a chain reaction. Alternatively, use high-durability walls to block explosions from damaging other turrets and your colonists.

Turret chokepoint

Putting a turreted defense in a chokepoint with a narrow entrance and wide turreted area is best because it forces the raiders to take a single-file approach to where all the turrets will be able to fire on them.

There should be more than one line of turrets so that the innermost line or lines can be used to position colonists where they are not immediately under threat from grenades (grenadiers will target the closest turrets first) or if colonists are positioned closer so they can repair, to retreat colonists further back when turrets are about to be or have been destroyed. Every line of turrets should have a line of sandbags directly in front and every supporting wall/rock should also have sandbags to lessen the likelihood of collapse due to collateral damage.

Turrets should not be placed directly (within three tiles) next to other turrets for the same reason, as they have a chance to explode when critically damaged. Placing walls between the turrets can lessen the impact of explosions, allowing you to put them tighter, but remember walls can block line-of-sight and bullets.

Power management

Turrets should be turned off whenever not in use. However, it's hard to anticipate when they will be needed, given the random nature of events in RimWorld, and turning them on by then is usually too late.

To fix this, connect your turrets to a separate power network, reconnecting them if needed. To toggle them all at once, install a power switch in a convenient location. The power switch can be then used to easily toggle a lot of turrets at once, saving power.

Weaknesses

Turrets are vulnerable to explosives and EMP damage.

• Explosives deal immense damage to turrets. All forms of regular explosives wielded by raiders are capable of 1-hitting a steel improvised turret and leaving a plasteel one at less than half health.
• EMP stuns the turrets. Enemy EMP grenadiers can stun a turret for 20 seconds with each grenade, meaning they can constantly lock down multiple turrets, especially those put close together.

Long-ranged gunners can shoot from outside their range without retaliation from the turret.

Mortars

A mortar attack on siege and raids can be effective while the attackers are still preparing. It's fun and most times raiders would flee before begin their assault due to huge losses of men during preparation.

It also allows you to effectively utilize your colonists who are poor at combat, as mortar accuracy is unaffected by colonist skill, however colonists incapable of violence will outright refuse to man a mortar.

Always to remember to manually unassign colonists from mortars; if you don't, they will continue standing there until they eventually collapse from exhaustion, starvation, or have a mental break.

An important point to remember is that while your colonists are better at dealing with single or spread-out enemies, mortars are designed for heavily grouped enemies. If you diffuse your enemies, the mortars will not be able to hit the enemies easily.

Mortar emplacements

Mortars need to be placed outdoors, so have shelves to hold the mortar shells. Set them to accept mortar shells only otherwise your colonists will haul random objects to the shelves.

Mortars also explode when damaged. Most of the time this isn't an issue, but if you're facing against a siege, an enemy mortar shell that scores a hit on your mortars can cause a chain reaction to rip apart your entire mortar emplacement, killing any crew manning it. To fix this, separate the mortars with high-HP walls that can survive at least 1 hit from an exploding mortar. Building mortars with plasteel also allows the mortar to survive a mortar hit, provided that the mortar shells don't explode.

Mortars can't fire at anyone within 30 tiles of it, so you will need to place the mortars deep inside your base for maximum coverage. It needs to be well-protected against intruders, for enemies that survive to come close to the mortars can wreck havoc on the helpless mortar crew, so you should pay attention and unassign the mortar crew to fight if necessary. It's best that you have your colonists standing guard outside, but if you need to you can always have a few pillboxes to defend the mortar base.

Explosive mortar battery

The most straightforward way of bombarding enemies, this simply involves building regular explosive mortars.

Due to inaccuracy, it takes at least 4 mortars to be effective, and around 8 mortars will be enough for most attacks. If you really want to overpower the enemy, 12-20 is good enough for a dense hail of mortar shells for dealing with endgame-level swarms. Any more is generally overkill unless you're facing up some really slow and tough enemies (such as centipedes).

Note that shield belts can easily mitigate the damage from the mortars, so be careful when facing enemies equipped with these. It's best to use EMP mortars, detailed below.

Incendiary mortars

Incendiary mortars deal low damage, penetrate shields and set areas on fire. The fire can cause disruption among the enemy ranks, as they frantically run trying to put out flames.

It can be paired with brawlers, which allows them to close in with less firepower on them, and force the enemy into melee combat, preventing them from extinguishing the flames on them. Be careful not to hit your colonists though.

Be careful with incendiary mortars as the fires can spread across wide areas causing extensive collateral damage.

EMP mortars

EMP mortars are a highly situational weapon, yet are useful enough to warrant their placement in every well-built defense. It doesn't deal any physical damage whatsoever, but are useful against some specific enemies. It's recommended that you have around 4 in each base.

EMP mortars are a must-have in case of a mechanoid raid. They stun them for a whole 90 seconds (much longer than the reload time of the mortars), allowing your colonists to close in on them and concentrate fire, or even engage in melee safely. You can simply keep the mortars firing when engaging the mechanoids, even if you're using melee; you don't need to worry about the mortars injuring your soldiers.

They also excel at dealing with shields, instantly downing many at once with its large blast radius and high EMP damage, making them an excellent weapon against full melee charges.

Traps

As you unlock research, and obtain more manpower and resources, you can lay more traps to debilitate incoming raiders.

IED traps

Early on, you may want to focus on armed colonist defense with turrets, but as the raiders grow in number, it becomes more efficient to use a bit of metal to kill several at once than to invest a lot of metal in a turret that costs nothing to fire, but will explode rapidly due to large raider groups.

IED traps are extremely effective when used correctly, however in open areas they are mostly useless as the raiders are highly unlikely to step in any of the traps, and even if they do they're not tightly packed enough for the trap to cause serious damage. Thus, it is better if you combine traps with funneling to force the raiders together.

1 IED trap can trigger other IED traps in its explosion radius. This may or may not be desirable depending on the situation; you can easily set off a chain reaction to destroy a whole incoming raider horde, but also use up much more resources. They also damage nearby structures, such as walls or deadfall traps, so don't put too many.

IED traps have a delay before exploding, allowing some raiders to escape. Raiders will attempt to run from an exploding trap, though the fuse is short enough to catch some of them.

Pros

• High area damage
• Raiders usually less protected against explosives

Cons

• High resource cost
• Single-use, non-rearmable
• Requires research
• Does not instantly trigger

IED incendiary traps

A variant of the IED trap that sets enemies on fire. It's a more situational pick compared to the regular trap, due to its incendiary nature.

Pros

• Distracts enemies while they are on fire
• Does not have a fuse
• Penetrates shields
• Raiders usually less protected against heat damage

Cons

• Low damage
• Not effective against mechanoids

Its use requires strong support to be effective. With that, it is a good defensive choice against heavily armored, shielded or fast enemies, with the flames providing good distraction while your colonists shoot them down.

It synergizes great with brawlers, which will prevent the enemy from attempting to extinguish the flames while fighting.

Mountain trap

An extreme version of the roof trap using overhead mountains instead of constructed roofs.

To use it, you mine out a whole mountain except a pillar in the center. Then you damage that pillar until it has just a sliver of health left (40 or less for easy activation with a single sniper rifle shot). Mining out all the rocks at once will result in your colonists getting crushed by the trap.

It is triggered the same way as the regular roof trap, and has the same effect radius except victims are instantly killed and buried. The collapsed rocks spawned after this trap is triggered can be useful or harmful depending on the situation.

Rearming it is a lengthy process as you will have to mine out lots of rocks. This does provide a decent way to train miners though.

Pros

• Instantly kills any enemy
• Leaves no corpses

Cons

• Takes much longer and is more dangerous to re-arm
  • You have to mine out everything then support the mountain roof with low-HP wall; compare with regular roof trap which simply requires building the wall and the roofs
  • Colonists risk death if you aren't careful
• No loot or capturable downed raiders
• Overhead mountains may not be easily available

In mountainous areas where overhead mountains are abundant, this trap can absolutely destroy any incoming raids, especially when combined with funneling.

"Attention Suppressor"

A full-size attention suppressor with a 1-wide path, built out of granite.

Once you have lots of bulk materials, but don't have enough industry to build proper defenses, you can build an attention suppressor out front of your basic defensive line. This is usually out of wood, although the flammability of wood is a problem.

Start like you're making a 29-wide room, but instead of doors, just leave one-tile openings at opposite ends. That way it doesn't get a roof. If needed, use a no roof area. Down the middle of the attention suppressor leave an open path, which will actually be traveled by your colonists. Pack the sides with alternating walls, leaving numerous blind alleys branching off the open path. The attention suppressor should look like two giant combs facing each other across the path, or perhaps like a cutaway of an especially-blocky sound suppressor.

A raider entering through an attention suppressor is presented with numerous blind alleys, each one of which could hold something important (in their perspective). Raiders will typically only resist the lure of a dozen or so blind alleys, after which they'll turn off into a blind alley to look for something to attack. In many cases they'll attack the walls, but the general effect is that a raiding force will spend a long time milling around in the attention suppressor, deeply distracted, and slowly trickle out of it toward your base alone, or (for a large raid) in twos and threes. This slow trickle of raiders is easily handled by a few colonists with basic weapons, or later a few turrets and a repairer.

Colonists and visitors with specific business on one side or the other of the attention suppressor will go quickly down the middle without being distracted. However, colonists pursuing joy activities like going for a walk will usually be diverted to do so in the blind alleys of the attention suppressor. As a result, it's not safe to fill with deathtraps.

Pros

• Effectively distracts and delays raiders

Cons

• Does not deal damage
• Takes up large amounts of space
• Expensive and time-consuming to build a lot of walls
• Makes it harder to eliminate all raiders at once

Overall, this can be a decent solution to delaying raids in early-mid game if you have the effort and materials, but as you enter mid-late game it's better that you replace the suppressor with something else (such as a killbox) which can actually bring the hurt.

Killboxes

Killboxes are in general heavily trapped, armed areas where enemies are funneled to so they can be destroyed easily.

They almost consist of a funnel which directs raiders into it, like a wall with a single opening.
Raiders will then trickle in, allowing colonists or turrets to concentrate fire on them, or traps to destroy them while they try to move in to attack.

This is an extremely effective way to defeat most raids, as the enemies will often be overwhelmed by the sheer firepower raining on them. It also allows effective use of traps, as funneling enemies greatly increases the chance one's going to trigger them. A well-built killbox can easily neutralize the threat of raids, to the point where some players refuse to use them since it takes the fun out of the game.

Note that sappers will attempt to mine into the base away from the killboxes, so make sure you have an effective coping strategy.

Building

You should double wall your killboxes as the sheer firepower raining on your enemies will inevitably destroy some of your own walls by accident, allowing raiders to flood into the killbox from another direction, bypassing traps and overwhelming your defenders.

Include sources of cover from around the killbox where your colonists can fire on incoming enemies. For increased firepower you may build turrets as well.

Entryways

Any entryways of the killbox should not be straight, otherwise raiders will simply fire using the entryway as cover. Instead, you should have a turn to break line of sight, prompting the raiders to enter an area where you can get them easily. For better effect, put a grave or other similar object that raiders can't stand on.

The below shows the results of different killbox entryways.

• 

  Right design of a killbox entryway. Raiders are prompted to move into the killbox, sometimes so close that they prefer to melee attack instead of shoot.

• 

  Wrong design of a killbox entryway. Raiders are bunching up in the entryway, using its walls as cover.

Don't make your entryway excessively long, otherwise raiders will think it's not worth it going such a distance and will decide to go for something else instead. Manhunters however will still chase colonists down a long corridor or over extreme distances, so you can have some dedicated anti-manhunter killboxes with extra-long corridors for this purpose.

For better effectiveness fill the entryway with deadfall traps, some IED traps (not too close to each other, otherwise they will set off a chain reaction) to soften the raiders before you fire on them, and alternated chunks or sandbags to greatly slow them down. Make sure that the walls are durable enough to withstand explosions if you will be using them.

If your entryway is long then you will need to build doors to allow your colonists to enter without setting off your own traps or having to go through all the obstacles.

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  Entryway with alternating sandbags to slow raiders and doors to provide access. Slows raiders but not colonists.

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  Same entryway but with deadfall traps. Deals heavy damage to incoming raids but costs a lot to build.

Equipment

Colonists defending in a killbox will be shooting at a large number of targets no more than a few tiles away (usually). Thus, defenders should use close ranged high damage weaponry for firing at raiders.

• Charge rifles, heavy SMGs, pump shotguns or LMGs work good in killboxes, being able to dish out hurt at close-mid ranges.
• Chain shotguns inflict extreme pain at killbox range, even surpassing the charge rifle in DPS as long as the targets are closely grouped.
• Miniguns are excellent at attacking the bunched-up raiders inside a killbox. While it won't hit its intended target, it will hit everything right next to it, inflicting heavy damage.
  • For maximum effectiveness focus it on a crafting spot at the exit of your killbox where your colonists will face the invaders. Remember to have fortified walls as many bullets will hit them instead of the raiders.
• Bolt-action rifles or assault rifles are useful for larger killboxes for reaching further targets, though they are not recommended for smaller ones due to their lower DPS.
• Don't bother with sniper rifles as they can't deal enough hurt to be effective at close ranges.
• Grenades are good if you can time them right. Throw them at the entrance where each explosion to hit a tight group of raiders, especially if they're slowed down with obstacles. Don't throw too many otherwise you'll demolish the walls of the killbox.
• Have melee colonists with longswords standing nearby as raiders who enter your killbox may decide to melee charge you instead.

Turrets

You can put turrets in place of colonists in a killbox. They deal moderate damage at close ranges, with the restricted space of the killbox offsetting the underwhelming long-range damage of the basegame improvised turret. A few can be deployed to provide additional firepower, ensuring victory.

You may also choose to fully arm your killbox with turrets, with enough to single-handedly take out raids (especially in tandem with traps). Doing this allows you to defeat raids automatically without the need to divert colonists from other jobs, but eats up lots of power and is vulnerable to solar flares, so you will need to have a backup plan.

Situational constructs

Crashed ships

Versus Poison ship and Psychic ship: Mechanoids have long agro range around 40 tiles from their spawn point. The larger the map, the easier it can be to deal with them, as long as the ship crashes away from your base. Though these ships are "time bombs", instead of immediate action, you can spend a few days building preparations before engaging them. Use the "Plan" feature in the Orders menu to draw a 40 tiles straight line so that you can have a visual length field and build one or two "Fire Walls" based on your weaponry. With bows of 30 tiles range, you will need a middle wall and a last wall, the first just to lure them with cover and the second to fire at them. Place some deadfall traps right in front of your sandbags, and rearm them as needed. Always make sure you have a safe pathing between your last wall and your base, so that when you see them coming fast at you, there's safe cover nearby until they retreat back to the ship, at which point you can repeat the same procedure.

You should use EMP mortars to stun the mechanoids, making them helpless hunks of metal. As they tend to spawn very tightly packed, the EMP mortar blasts are extremely effective against them, being able to stun a large number at once. As the ship part also blocks EMP pulses, build multiple mortars to fire a volley, in order to hit all the mechanoids at once.

Building IED traps right next to the ship will instantly trigger the ship's mechanoids to swarm out. However, building them 1 tile away does not trigger it, allowing you to use them to weaken a mechanoid swarm (though you may have to manually trigger them). Don't build too many or you will vaporize the mechanoid corpses which can be deconstructed for resources.

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Guides

Progression

Quickstart Guides • Basics • Intermediate Midgame Guide • Advanced Endgame Guide • Ending the game

Scenarios

Lost Tribe Guide • Rich Explorer Guide • Naked Brutality Guide • The Mechanitor Guide

Survival

Extreme Heat Guide • Extreme Cold Guide • Extreme Desert Guide • Ice Sheet Guide • Sea Ice Guide • Events Guide

Combat

Defense tactics • Offense tactics • Weapon Guide

Construction

Colony Building Guide • Defense structures

Production

Food production • Money making guide

Other

Skill Training • Permadeath save conversion guide •
Ideology Min-Maxing

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Architect

Security

Barricade • Sandbags • Spike trap

(research)

Autocannon turret • Foam turret • Mini-turret • Rocketswarm launcher • Uranium slug turret • Mortar

IEDs

IED trap • IED incendiary trap • IED EMP trap • IED firefoam trap • IED smoke trap • IED antigrain warhead trap • IED tox trap • IED deadlife trap

Related

Antigrain warhead • EMP shell • Firefoam shell • High-explosive shell • Incendiary shell • Smoke shell • Tox shell • Deadlife shell