Raider

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Raiders are enemies that spawn in groups at semi-regular intervals. Group size, health, skill, and equipment depend on both the set game difficulty and the time already elapsed in the game. Typically on Tough Cassandra Classic only one wounded raider spawns in the first group. The subsequent group has 3-5 raiders, and eventually, there are groups of more than 20 raiders with the lowest health being above 80. Raiders will invoke a message when they spawn, and an alert will come when they begin their assault.

Raiders can enter "steal" mode if they see enough value. In this mode, they will grab your stuff and carry it off.

If the raiders see that they are losing, they may most likely flee, or try and kidnap downed colonists by letting some do the actual kidnapping and some covering them. After one of your colonists has been kidnapped, a ‘ransom demand’ incident can fire, demanding silver for the colonists that has been kidnapped.

They can spawn with both ranged or melee weapons, all melee with personal shields (for Pirates or Outlanders), or all ranged.

As of version 0.15.1279 (29 August 2016) raiders steal a bit more often now.

Equipment

Raiders have limited equipment possibilities. Usually on Cassandra Classic they come equipped early on with mostly pistols and crude melee weapons, some survival rifles and pump shotguns later down the line. In the late game they can come equipped with things such as frag grenades, sniper rifles, incendiary launchers and machine pistols. Rarely some will have assault rifles or even Charge Rifles. A raiding party may include members equipped with melee weapons and personal shields. When a raiding party includes grenade throwers, the AI is intelligent enough to run way from grenades thrown by their own faction.

As of version 0.14.1234 (15 July 2016) the AI dressing algorithm is now better at making outfits to withstand cold temperatures. If there is no way to make a survivable outfit, pawns won’t arrive at all. No more raids arriving and keeling over in -60C weather.

Raider Types (Humanlike)

There are multiple types of Raiders in RimWorld, each with their own sets of equipment and budgets. Raider types are exclusive to their faction.

Pirates

The following is a list of raider types exclusive to Piratebands, in order as shown in Defs:

Drifter

Drifters are effectively the cannon fodder of pirate raiders, wielding no more than a sub-par quality club, occasionally a shiv - or rarely: a knife. They are normally either naked, or seen sporting a tattered pair of pants or t-shirt also of sub-par quality. Drifters also have a 20% chance of sporting some form of crude headgear, and a 10% chance of rocking a Peg Leg for that Pirate look. Drifters are only encountered in your very first raid (or on very low difficulties), and they prove to be of very little threat. Pirates also care so little for their drifters that they don't even send them with food.

It is listed in the weapon tags that Drifters may show up with guns, but they don't appear to actually bear firearms about their person.

Combat Power: 25
Average Gear Health: 40%
Average Gear Quality: Shoddy
Clothing Budget: 90-280 Silver
Weapon Budget: 60-100 Silver
Silver Carried: 30-70 (10% chance)
Medicine Carried: 1 (10% chance)
Minimum Age: None
Maximum Age: None

Scavenger

Ranked above the Drifters; Scavengers have the privilege of actually equipping firearms as opposed to paltry low-quality melee weapons. Their equipment will still generally be of bad quality - but a massive step above what Drifters have to put up with none-the-less. Scavengers are most often seen with Machine pistols, Pump shotguns, Survival rifles, and Incendiary launchers; but they can also be seen rocking Pistols, Heavy SMGs, and even LMGs. Scavengers also typically have multiple items of clothing on them, but never armoured vests.

Scavengers have a 30% chance of spawning with headwear, and a 10% chance of being hindered by a Peg Leg. Scavengers typically accompany your average second-to-fourth-or-so pirate raid, depending on wealth and difficulty; and are therefore still not a truly significant threat, but you should still be cautious at the stage of which you'll typically fight them.

Combat Power: 38
Average Gear Health: 55%
Average Gear Quality: Poor
Clothing Budget: 300-500 Silver
Weapon Budget: 250-450 Silver
Silver Carried: 25-50 (10% chance)
Medicine Carried: 1 (10% chance)
Minimum Age: None
Maximum Age: None

Thrasher

Thrashers are a direct step up from Drifters; typically being seen with higher quality melee weapons, but they are still generally limited to clubs, shivs, and knives - with clubs still being the most common, but knives and shivs are roughly equally likely. They are also often seen wearing headgear, and they have a generous apparel budget (for their rank), but they still have a poor weapon budget which limits them to poor melee weapon types. Thrashers have an 80% chance of coming with a hat, and a 10% chance of rocking the stage with a Peg Leg. There is a chance that a Pirate Leader could show up in a raid as a Thrasher.

Thrashers are only seen early game, and are soon replaced by the advanced Slashers, so they'll generally only feature in around one or two raids under typical circumstance. They pose a minor threat, but nothing too significant.

Combat Power: 36
Average Gear Health: 75%
Average Gear Quality: Poor
Clothing Budget: 300-800 Silver
Weapon Budget: 60-150 Silver
Silver Carried: 25-50 (10% chance)
Medicine Carried: 1 (10% chance)
Minimum Age: None
Maximum Age: 48 Years

Pirate

Pirates are a step up from Scavengers, with further improved weapon and clothing budgets. As a result, Pirates can potentially be a moderate threat to the colony should one not take sufficient care in dispatching of them. Pirates are typically equipped with higher grade firearms such as Assault rifles and LMGs; but are also often seen with Pump shotguns, Survival rifles, and Heavy SMGs, and less oft seen with Sniper rifles, and rarely Machine pistols and Pistols.

Pirates may also sport Armoured vests and Devilstrand clothing. There's a 70% chance they'll be wearing a hat, and a 10% chance they'll have a peg leg.

Combat Power: 56
Average Gear Health: 95%
Average Gear Quality: Normal
Clothing Budget: 500-1100 Silver
Weapon Budget: 450-600 Silver
Silver Carried: 40-80 (10% chance)
Medicine Carried: 1 (10% chance)
Minimum Age: None
Maximum Age: 50 Years

Outlanders

The following is a list of Raider Types exclusive to Outlander Towns.

They are not strictly 'raiders' as they are often friendly and visit the colony or escort a trade caravan to your base.

Town Councilman & Town Trader ('Villager' based)

These two types of Outlanders are often found in trade caravans or as visitors, and are put together because they share the 'Villager' pawn kind. Villagers will typically be fully clothed and will have basic weapons of both the melee and firearm variety: usually clubs, knives, maces, and pistols.

Combat Power: 25
Average Gear Health: 110%
Average Gear Quality: Poor
Clothing Budget: 300-900 Silver
Weapon Budget: 0-250 Silver
Silver Carried: 25-70 (22.5% chance), 700-1000 (2.5% chance)
Medicine Carried: None
Minimum Age: None (Town traders), 40 (Town councilman)
Maximum Age: None (Town Traders), 100 (Town councilman)

Town Guard

Town Guards are moderately powerful outlanders which can be seen accompanying Outlander Trade Caravans, or in hostile Outlander raids. Town Guards are most often seen with Pistols, but can also be seen with Machine pistols, Heavy SMGs, Pump shotguns, Survival rifles, Incendiary launchers, Sniper rifles - and even LMGs and Assault rifles.

Combat Power: 50
Average Gear Health: 115%
Average Gear Quality: Normal
Clothing Budget: 300-900 Silver
Weapon Budget: 200-600 Silver
Silver Carried: 30-100 Silver (5% chance)
Medicine Carried: None
Minimum Age: None
Maximum Age: 65 Years

Tribal

The following is a list of Raider types exclusive to glorified manhu - I mean tribes:

Warrior

Tribal warriors are your standard... tribal warriors! They appear in Tribal raids equipped with nothing but Clubs, and occasionally Spears, and they only wear Tribalwear - or Parkas if necessary. Individually, they're a moderate threat at most - but they can be a considerable threat and potentially overpower your defensive line due to the sheer numbers that they occur in.

Combat Power: 38
Average Gear Health: 115%
Average Gear Quality: Normal
Clothing Budget: 180-350 Silver
Weapon Budget: 60-400 Silver
Silver Carried: None
Medicine Carried: None
Minimum Age: None
Maximum Age: 40 Years

Archer

Archers are somewhat self-explanatory in their titles: they assault in masses, and let off a cloud of arrows (or pila) which could poke an eyeball or two. Archers typically utilise Pila and Great bows, but they may rarely sport Short bows too; and they wear your standard Tribalwear, and Parka if the conditions are too harsh to go without. Archers equipped with Pila and Great Bows are dangerous as a Pilum in the wrong place can render a colonist useless, or even kill them, and Great bows are effectively Wooden Survival rifles.

Combat Power: 48
Average Gear Health: 115%
Average Gear Quality: Normal
Clothing Budget: 180-350 Silver
Weapon Budget: 60-400 Silver
Silver Carried: None
Medicine Carried: None
Minimum Age: None
Maximum Age: 40 Years

Chief

Chiefs are hardened, high-ranking tribals which have endured the heat of battle and the hardship of survival on the Rim, and so far made it through alive. They only get the best weapons that their tribe can possibly make, but they are ultimately glorified Archers which may have a chronic disease or few. Chiefs will only be found equipped with Pila and Great bows, of which some could be Excellent or even Masterwork quality. Chiefs are also more difficult to recruit as colonists if they survived to be imprisoned.

Combat Power: 70
Average Gear Health: 185%
Average Gear Quality: Superior
Clothing Budget: 600-1600 Silver
Weapon Budget: 800-1000 Silver
Silver Carried: None
Medicine Carried: None
Minimum Age: 35 Years
Maximum Age: None

Mercenaries

Mercenaries are usually encountered in mid-game raids onwards, and will usually be found in Pirate raids, but can also be mixed amongst Outlander raids - but never Tribal raids. Mercenaries are high-ranking soldiers which have high budgets for weapons and clothing, and are usually encountered wearing an armoured vest. There are several variations of mercenaries:

Mercenary Gunner

Mercenary gunners are the weakest mercenaries out of the lot, but still pose a moderate to considerable threat with their numbers. Gunners will spawn with pretty much any mid-range weapon with near-equal commonality: from Machine pistols to LMGs and Sniper rifles, and in-between - but never pistols. Gunners will also usually wear armoured vests, along with Kevlar helmets, Military helmets, and rarely even Power armour helmets - and they'll occasionally be seen wearing Hyperweave clothing.

Mercenary Gunners also have a 0.3% chance of spawning with a bionic body part. Mercenary gunners can also be seen with Combat Enhancing Drugs.

Combat Power: 70
Average Gear Health: 150%
Average Gear Quality: Normal
Clothing Budget: 1500-2800 Silver
Weapon Budget: 400-900 Silver
Silver Carried: 50-200 (20% chance)
Medicine Carried: 1 (20% chance)
Minimum Age: None
Maximum Age: 65 Years

Mercenary Sniper

Mercenary snipers are... well, snipers! Their clothing budget is overall slightly lower than a Gunner's, but they have an improved weapon budget, and always spawn with a long-range weapon, the Sniper Rifle. Everything else remains the same.

Combat Power: 90
Average Gear Health: 150%
Average Gear Quality: Normal
Clothing Budget: 1500-2500 Silver
Weapon Budget: 1200-1800 Silver
Silver Carried: 50-200 (20% chance)
Medicine Carried: 1 (20% chance)
Minimum Age: None
Maximum Age: 65 Years

Grenadier

Grenadiers can prove to be somewhat of a threat towards both colonist lives and structures alike. Grenadiers are identical to Mercenary gunners, except they mainly utilise grenades and molotovs, and also have a considerably lower clothing budget.

Alternatively, they may come equipped with EMP grenades, and will be called EMP grenadiers. These deal no damage but can stun turrets and down personal shields', spelling trouble for turret-based defenses or shielded melee fighters.

Combat Power: 60
Average Gear Health: 150%
Average Gear Quality: Normal
Clothing Budget: 800-1400 Silver
Weapon Budget: 600-1000 Silver
Silver Carried: 50-200 (10% chance)
Medicine Carried: 1 (10% chance)
Minimum Age: None
Maximum Age: 65 Years

Mercenary Slasher

Slashers can prove to be a real threat to front-line gunmen due to their use of Personal shields and high-quality melee weapons. A typical slasher can be overwhelmed by a couple of people beating the living daylights out of them, shooting them at point-blank range, or with concentrated fire from a distance; however, they can and will often come in large numbers, in which they can cause great trouble. Slashers have an 8% chance of spawning with bionic body parts.

Combat Power: 135
Average Gear Health: 140%
Average Gear Quality: Normal
Clothing Budget: 1000-2600 Silver
Weapon Budget: 1200-2000 Silver
Silver Carried: 180-400 (20% chance)
Medicine Carried: 1-2 (20% chance)
Minimum Age: None
Maximum Age: 65 Years

Heavy Mercenary

Heavy Mercenaries are a force to be reckoned with in terms of firepower, and should be prioritised as a target in most combat situations. Heavy Mercenaries are specialised with heavy weaponry; and will therefore utilise Triple rocket launchers, Doomsday rocket launchers, and miniguns. Despite packing serious heat, Heavy Mercenaries have a poor clothing budget, and will therefore not be very well protected against sustained fire. Heavy mercenaries have an 8% chance of spawning with a bionic body part.

Combat Power: 185
Average Gear Health: 95%
Average Gear Quality: Normal
Clothing Budget: 200-350 Silver
Weapon Budget: 1600-2000 Silver
Silver Carried: None
Medicine Carried: None
Minimum Age: None
Maximum Age: 65 Years

Elite Mercenary & Boss

Elite Mercenaries and Bosses are functionally identical, so the information here applies to both. Despite having a higher 'Combat Power' rating, it is arguable that Heavy Mercenaries will still pose a more significant threat than Elite Mercenaries, purely due to their explosive arsenal. However, Elite Mercenaries have exceptionally high equipment budgets, and are not to be messed with at all. They often utilise power armour helmets and devilstrand/hyperweave clothing, but never power armour. Their arsenal consists solely of LMGs, Assault rifles, and Charge rifles. Elite mercenaries have an 8% chance of spawning with a bionic body part.

Combat Power: 220
Average Gear Health: 215%
Average Gear Quality: Normal
Clothing Budget: 2500-4200 Silver
Weapon Budget: 1600-2000 Silver
Silver Carried: 120-480 (20% chance)
Medicine Carried: 1-2 (20% chance)
Minimum Age: None
Maximum Age: 45 Years

Raider Types (Mechanoid)

Main article: Mechanoid

The following is a list of all mechanoids that can show up in raids.

Scyther

Scythers are fast-moving, and particularly dangerous against isolated targets due to their high shooting accuracy and their potential to instantly destroy vital organs, and risk of loss of limb - or even life - when facing one. Although Scythers are dangerous to confront at longer distances if you don't have any bionically augmented or careful marksmen, they can generally be quickly overwhelmed by a small firing squad at closer range. They always come equipped with a charge lance, which is comparable in overall firepower to a survival rifle. Scythers are also highly competent at melee, and it's generally a bad idea to send somebody in without very high quality armour, a personal shield, and a minimum of a mediocre plasteel longsword.

Combat Power: 160
Average Gear Quality: Normal
Weapon Budget: 5000 Silver

Centipede

Centipedes are the opposite of scythers: slow-moving, lumbering hunks of metal that can take a considerable beating to take down. As they move so slowly, it is almost feasible to pound them with mortars if possible - as opposed to risking a colonist's life and limb. Although generally of little threat to solitary targets due to forced miss radius (unless wielding an inferno cannon) due to forced miss radius, centipedes can be highly destructive against groups of people that dare step in their way. Centipedes can be equipped with miniguns, heavy charge blasters, or inferno cannons.

Combat Power: 290
Average Gear Quality: Normal
Weapon Budget: 8000 Silver

Raiders' Strategies

Immediate Attack

Raiders, upon either landing in their drop pods or arriving on the map sides, will proceed to instantaneously converge on your colony and attack. The best thing to do is to defend.

Immediate Attack Smart

Like Immediate Attack, but the raiders are unusually clever in their tactics because they simply steal some of your items and run. This can be devastating in early game, because a raider may steal your stockpile of components, leaving you without any means of using electricity.

Preparation

Raiders, upon either landing in their drop pods or arriving on the map sides, will proceed to stand around in a small group near-by where they spawned for a period of time and then proceed to attack. It is possible and a completely viable strategy to attack them while they are "preparing". This preparation has no effect on their attack other than the fact that it gives you more time to prepare yourself.

Sappers

Raiders, upon either landing in their drop pods or arriving on the map sides, will proceed to instantaneously converge on your colony but not attack. They will instead mine a separate way into your colony away from your defenses.

This can be a fairly dangerous way (to you) for them to try and attack, especially in mountain bases which tend to have defenses concentrated at the entrances. The best thing to do is instantly assault them before they can mine too much.

On the other hand, in most open bases, they are mostly no better than regular raiders, and can be dealt with as such.

Siege

Raiders, upon entering the edges of the map, will proceed to receive supplies (steel, packaged survival meals, components, and mortar shells) from drop pods and construct any number of the following:

• Mortars
• Incendiary Mortars
• Sandbags

They will always construct two mortars, regardless of the number of raiders.

After constructing the amount they desire, they will proceed to bombard the colony with mortar shells, potentially causing a great deal of damage.

During the siege, food and mortar shells will be continuously replenished upon running out through drop pods, with each containing 12 of packaged survival meals or shells.

Oddly, they rarely use the best constructors when building.

Defense Strategies

Raiders will attack randomly chosen constructed objects and colonists. They will not attack prisoners, natural rock walls (not the case for sappers, animals (unless the animals are hostile or tamed) or unpowered turrets. Raiders will usually set fire to crops in growing zones, power generation or conduits, walls, nutrient paste dispensers, equipment racks, orbital trade beacons; they will melee-attack lamps, beds, stools, short tables, long tables, and doors; they also use molotovs and frag grenades on turretss, sandbags, or other targets, and some use EMP grenades to stun your turrets. It is thus recommended to keep power generation, eating areas, lighting, doors, and walls near or behind a protected entrance. Raiders will prioritize firing on colonists or turrets when those colonists or turrets are firing on them, but will otherwise prioritize random objects, meaning you can put doors or walls near your defenses to temporarily distract them.

Raider Preparation

Raiders will sometimes start by standing around in a group where they spawned and will continue this until they see a colonist nearby or they hit a certain preparation time limit, at which point they begin the assault. Because a colonist can set them off early, you can plan out the time you want them to attack. It is generally best to set them off early if you're well-prepared, to avoid potentially troublesome scenarios such as having no power when their timer runs out. Conversely, you should not set them off early if your defense is not prepared. Note that raiders usually take less than one day to begin, meaning that if there is an eclipse and you rely on Solar generators, you should not wait for them and should instead set them off early while you still have some power left. Also it's good to note that raiders will remember where your traps are. This doesn't apply to other factions, though -- if, say, the Vipers of Power come in and sets off your traps, then they would remember that. But, if the Rippers of Fire later attack, they won't have that knowledge and will still set off the same traps.

Siege defense

When faced with a siege, there are a few coping strategies you can use.

You can choose to either to assault the mortar base or wait it out and repair the damage as best as you can. The choice mainly depends on the surroundings of the mortar base and your base's position. If your base is located under a mountain (your base tiles will read Overhead Mountain when you hover your cursor over them), the mortar shells won't be able to hit those tiles at all! This makes deep mining a very effective strategy against heavy bombardment. If you don't build your base into a mountain, you should at least consider digging out at least one panic room for your colonists to hide within from the shells.

If you assault their base, one possibility is sniping either the shells or the mortars, hoping an explosion kills many of the raiders. If you want to leave those intact, you can snipe the raiders themselves, although killing them prompts them to assault your colony directly instead of sieging.

Incendiary mortars are an effective way of distracting sieges as the raiders will be preoccupied with extinguishing the resultant flames. This way, 2 mortars are enough to keep them from doing any activity other than firefighting, unless it is raining or there are no flammables nearby.

EMP mortars are extremely efficient siege-breakers; they can easily detonate the mortar shells, killing nearby raiders, as well as stun the mortars, preventing them from firing. Sometimes only 1-2 shells are enough to prompt them to attack.

Mortar Tactics

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.

Due to inaccuracy, it takes at least 4 mortars to be effective, and around 8 mortars will be enough for most attacks. Do note that each mortar needs its own shell storage, mortar shells can stack up to 25, you will need around 200 shells for 8 mortars to work effectively/automatically (manually un-man the turret can solve this issue)

Note that personal shields can easily mitigate the damage from the mortars, so be careful when facing enemies equipped with these. EMP mortars are a good way of dealing with shields, as they instantly down them and have a much larger radius.

Melee charges

Pirates or Outlanders can come with all melee charges complete with personal shields. This can prove an extreme threat to colonies, especially as they charge towards the colonists directly with their personal shields blocking large amounts of gunfire.

However, they are often poorly equipped, aside from the shields; they aren't particularly well-clothed or armored, and their weapons are often of low quality. They are also highly vulnerable when their shields are down.

Ideally you will want to have a few brawlers on your own, preferably with better equipment, such as full armor and quality weapons to fight the incoming charge.

If you happen to not have enough brawlers to handle the charge, attempt to concentrate fire to break the shields, then kill any unshielded raiders. If they do come close, get your colonists to fire point-blank at them if it deals more damage than unarmed, otherwise assign 2 colonists to beat up each attacker.

Explosive weapons are not very useful on them due to their shields protecting them, but you can still try and break their shields with them.
Incendiary weapons penetrate the shield and set the raider on fire, distracting them. While their shields block gunfire, the distraction makes it easier for it to be broken, and makes there be fewer enemies engaging your colonists at a time.
EMP weapons can be used to devastating effect by downing their shields, leaving them to the mercy of your colonists' gunfire.

Mechanoid assaults

Mechanoids only come in 2 types, Scythers and Centipedes. They have much differing stats and weapons, meaning different tactics may be used.

In most raids where they come/ drop in at the edges, the Scythers will outrun the Centipedes by a great margin, giving plenty of time to deal with them before the centipedes.

Scythers are capable of long-range attacks, and are extremely deadly with melee. If fighting it from a distance, cover along with long-ranged weapons such as sniper rifles or survival rifles are vital.
Despite its high melee damage, sometimes melee fighting it may be better, as long as you have good enough armor and weapons.

Tribal raids

Tribal raiders come in large numbers, but with relatively poor equipment; as such, it requires a different strategy compared to pirate or outlander raids.

Overall, they can deal heavy damage to your colonists; they do not have good weapons, but compensate with their sheer numbers.
However, as tribalwear does not provide protection and they do not wear any form of armor, they are easier to kill individually than other raiders.

Crowd control is an important aspect in defeating tribal raids. The Minigun or LMG is an effective weapon to use as it can easily mow down groups of raiders.

Their archers are dangerous

Removing rock chunks also helps in dealing with tribal raiders hiding behind them, making them much easier to hit.

Dealing with Explosives

Raiders wielding explosives can be a serious threat to colonists, especially those equipped with the Doomsday rocket launcher or triple rocket launcher.

Thrown explosives

Raiders with thrown explosives are horribly short-ranged, giving your colonists a chance to shoot them down before they can even throw a single grenade.

As frag grenades have a fuse and small radius, evacuating colonists can safely avoid the damage.

Molotov cocktails explode instantly, and can set your colonists on fire; while they do not cause as much direct damage as frags, they can cause your colonists to exit cover and run around erratically, exposing them to gunfire. Downed colonists will certainly die from fire unless extinguished or rescued.
The fires started can also be damaging to your base and can burn down vital structures such as power conduits and generators.

Incendiary launchers are functionally the same, however they have a longer range, making them harder to deal with.

EMP grenades are less dangerous overall, as they do no physical damage; still, they pose some threat to melee brawlers by downing their shields, as well as stun turrets.

Rocket launchers

Raiders with rocket launchers are arguably more dangerous, due to their long range and high damage explosive attacks that can easily down, maim or kill several colonists at once.

However, they are not good shooters; they don't have much qualms about injuring their comrades at all, even if there's only 1 lone colonist but many of their fellow raiders around them. This can be exploited simply by making a colonist equipped with a personal shield run towards them. They will often hit their allies, especially when using the Doomsday rocket launcher, while the shield will block the damage from the explosion.
Note that this is somewhat risky as your colonist's shield is likely to be broken from the resulting concentrated gunfire even if it did survive the blast; afterwards, your colonist may be injured, downed or even killed. Still better than having many colonists die from a rocket launcher though.

Alternatively, you can use one of your more expendable battle animals to charge the attackers; this has the same effect except your animal will most likely die from the rockets.

Defensive Construction

The below shows ways you can build a base to repel attacks.

Perimeter sandbags

An essential way to defend a large base if you don't want to build killboxes (see below) or the like, this simply involves surrounding your base with sandbags. This provides essential cover from gunfire, stopping 65% of the bullets that will otherwise hit your colonists.

Turret Nested Entryway

Turreted outside areas are generally only viable for the first several raids (in Tough Cassandra Classic), after which the areas will quickly get overwhelmed each raid due to not being able to focus fire on the spread-out raiders. While protecting the outside starting area, you want to rapidly pause the game during raids and give orders to repair damaged turrets. Turrets should each get their own sandbags to reduce incoming fire both to the turret and the colonist behind the turret repairing/shooting.

Putting a turreted defense in an underground base 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 wall/rock or other turrets for the same reason, as they explode when they run out of health. Outside or in front of the defense area, you can put blasting charge minefields in areas they are likely to group up in.

Remember that raiders will run from exploding turrets!

Minelaying

Early on, you 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, and the raiders will make some (but not usually enough) of an attempt to avoid them, which can force them into a single-file line even before they reach the entrance.

Note that IED traps have a delay before exploding, allowing some raiders to escape.

Killboxes

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

They almost always 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.

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.

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

"Attention Suppressor" Entryway

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 29×29 room(27×27 interior), 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, 3 tiles wide, which will actually be travelled 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.

Diagram:

#############   #############
#                           #
#############   #############
#                           #
#############   #############
#                           #
#############   #############
#                           #
#############   #############
#                           #
...and so on

A raider entering through an attention suppressor is presented with numerous blind alleys, each one of which could hold something important. 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.