Alright, this is something I've meant to do for quite a while but hadn't really gotten around to because, to be honest, it's rather involved. However, it's well worth doing because it's not only fundamental to fighting many armies that have the capacity to deep strike, but can singlehandedly defeat some strategies or even entire armies- most especially Chaos Daemons.
So today we're going to look at the techniques of castling and deep strike defenses for both "safe" deep strikes (like Drop Pods) and "risky" ones (like most other units that don't get a special exemption to the mishap rules.) I'll try and show how to set up to protect yourself from various kinds of threats that can deploy from DS and how you can maximize your space and time to fight an army that intends to use DSing to get in close with you as well as how to play the odds against them.
Alright, the first thing we need to cover is the basics of Deep Striking, just as a reminder. When DSing, you place one model of your choice from the unit on the board and roll for scatter, moving it the appropriate number of inches (except on a hit.) Next, you make a "ring" around the first unit placed, expanding it outward once and only once the original ring is completed, until all the models in the unit are placed. If, at any time, you can't place a model due to friendly units or impassible terrain being in the way, an enemy unit being within 1", or being forced to place one or more models off of the board., it results in a mishap and you roll on the table. Drop Pods and similar units almost always have exceptions that allow you to reduce scatter by the minimum needed to avoid a mishap. A model that lands in difficult terrain must immediately make a Dangerous Terrain test.
This gives us a couple of key points: dice averages mean that, without protection, arriving any closer than 8" or so is quite risky- more so the closer you try and get, although the odds never drop below 33% if there's room to place the unit in that space. Board edges and impassible terrain present similar dangers; difficult terrain may cause some casualties, but isn't particularly threatening. The typical size of DSing units means that you will need ~5" (for a 5man unit) or ~7" (for a 10man unit) diameter of empty space in order to land safely- for units any bigger than that it starts becoming rather impractical to try and DS with any degree of safety.
So we need to look at various types of deep striking units and what their goals are, what we have to worry about from that unit, and how to protect ourselves from them. We can fairly easily divide them into a few basic categories; the first and most common are units that want to DS near us in order to assault us- these are the easiest dealt with, as they rarely have DS protection in the normal forms. The second are units that want to DS us in order to Melta away a tank or other critical target- these are often harder to deal with. The third are protected deep strikes, which are the most difficult to deal with and often overlap with one of the two previous kinds, but need to be fought in a manner that takes some different qualities into account and thus will be discussed separately.
We also need to look at what our own army brings to the table and how it can handle the many different targets that arrive by DS, but this is such a broad-ranging question that I'm going to simply narrow it down into a few simple questions, namely "Do we have disposable infantry?" and "Do we have tanks?"
Now, before we get into the analysis, let's take a look at a fairly typical type of battlefield and figure out how we might use it to fight an army consisting mostly or entirely of deep strikers.
We'll be assuming that the hills are not difficult terrain, even on the edges, but can provide cover (even for tanks) and the two circular structures on the right side as well as the central structure are all impassible and LOS-blocking; the remaining pieces can all be considered area terrain.
So where would we want to be, given the option? Remember, most DSing armies will want to give you the first turn if they have the option, because it reduces how long you can shoot at them for, so as often as not we'll be given first turn, even when we don't win the roll-off. The top half of the board is distinctly better than the bottom for us- while the bottom still has some decent cover from many angles, the hill will provide effectively nothing for us in terms of disrupting their arrival. That's the first thing you should be looking for against a DS army- large pieces of cover, especially impassible ones, that are near board edges. You are looking to maximize their chances for a mishap and, consequently, maximize the distance they must arrive from you in order to be "safe."
So the top half is definitely our pick if we get the option, and the right side of the board is better than the left- again, those two big circular dome/cylinder structures will make things very awkward for them.
The assault marines mark our four preferred zones to be hanging out in when the enemy arrives.If we're forced to be in the upper left that isn't completely awful- there is enough terrain up there to make things a bit tricky for the enemy, but it's hardly ideal for our purposes. We must absolutely at all costs avoid deploying in the lower left, however- not only is there a paucity of terrain to slow or injure the enemy, it is also distant from all of the impassible pieces on the table making it difficult to try and scoot to them during our "free" movement on T1 before the enemy arrives.
The First Threat: Deep Striking Assaulters
This is the focus of this article not because these units are the most common or the most dangerous, but because it's the one that is actually the easiest to defeat and composes an entire army (Chaos Daemons) that can effectively have its back broken before a single shot is ever fired. An army that relies entirely on assaults that you can keep your distance from is an army that is a non-threat; this is why units like Fiends of Slaanesh are absolutely essential to making something that is even vaguely functional and it's why Bloodcrushers/Fatecrusher, Bloodletters, etc, etc, are just laughable in terms of being competitive.
First things first: an assault army is (duh) looking to make assaults on your infantry, generally because they think they can win (double duh). They are not, in most cases, going to want to assault your tanks, nor are such units going to have a way of arriving close to you without the aid of an Icon/Beacon/Homer/etc. This leaves you with a number of good options. Let's look at a sample deployment against such an army. (Actually, deployment is the wrong word here- this will be what you want to look like following your movement on turn 1.)
This is assuming a Marine army with six vehicles and 30 infantry models- hardly an unreasonable number even for a game in the 1750 range, in many cases, though of course they probably all aren't Rhinos and Tactical Marines. :P Our goal here is to fill space in a way that denies the Daemons places to arrive- note how more than 25% of the board is simply off-limits to them, with some very limited exceptions; this means that if they want to come in without extremely high chances of mishap, they are going to have to do so at a significant distance from our lines. We have also left ourselves room to make a fighting retreat, withdrawing to either the northeast or southwest of our original position here- this can buy us several more turns if we need them, and even if they surround us we can simply "collapse" the castle in on itself, drawing back to our corner and getting at least two turns of movement. This is an example of a fairly classic "castle" defense in its most general form.
It's also important to note the presence of the "trap" zones that have been marked with a Bloodletter in the above picture- these are areas where a small unit might technically be able to fit, but even the very smallest of deviations will result in a mishap. (The Bloodletters have all been given 2" auras in the picture to give you an idea how much space will be required to fit a small unit without mishapping- anything beyond that radius, whether by deviation or by squad members is probably going to get them killed.) Some players will go for these traps with gusto- and by all means, let them; two thirds of the time, this will result in their unit dying instantly, being completely useless for the rest of the battle, or being forced back into reserve; on the rare occasions when they land there successfully, they simply become your first target- and if your army can't eliminate a small unit with no cover, your problems run deeper than defending against deep strikers.
Such traps can and should be created using a combination of your own units, board edges, and impassible terrain, as in the illustration; difficult terrain, why helpful to your purposes, will not cause mishaps and thus should be effectively ignored when creating traps. (Note the unit of Marines hanging out in the "swamp" to make sure no Daemons show up there.) This is why deployment is so critical against a deep strike army- seizing a strong position to create the castle in can literally decide the course of the game then and there.
With all of that in mind, a reasonable Daemon player's arrival prospects for their first turn look something like this:
Blue auras mark rough threat/scatter zones.Attempting to come in on the top right is still very risky, even just for small or isolated units- and it's unlikely that such a unit is going to be able to stop the army from escaping up that direction if it is making a retreat. They may try and slip something in there as a distraction/blocker, but as likely as not they'll be forced to leave it open, as the most common scatter result (7" in a given direction) brings up a mishap almost no matter which way the arrow points. Top-center is a bit safer, and shifting further to the left safer still- but at the cost of increasing distances from their targets, giving the Marines more turns to weaken them with firepower. Realistically, the positions in the southwest are going to be the preferred arrival zone, even though it forces things to slog through difficult terrain to get to their targets; it is the only place there is enough space to bring down more than a small number of units without mishapping all over themselves.
So how do the Marines in their castle respond to this assault? Why, by drawing up the gates, of course!
As we can see here, even a measly 7" shuffle backwards by the transports and embarking one or two units, suddenly the Marine position is a lot further away than it was a few seconds ago. The Bloodletters, assuming nothing untoward happens to them on arrival, will end up well out of assault range and may still be out of range next turn, even with Running- the Marines, after all, still have plenty of space left to withdraw into. Almost none of the infantry in this picture have moved, allowing them to deliver full firepower to any Daemon targets in range, though the vehicles will only be shooting if they are Fast or took up different positions. For this turn, at least, it's simply a matter of target priority- shoot the things that get an assault next turn, ignore the ones that can't; with the limited number of targets on the table, it will more or less be a turkey shoot.
It's also worth noting that, like a more traditional castle, the "walls" of this formation are still very hard to breech- few assaulters relish the "hit on sixes, glance on sixes" world of trying to punch their way through a fast-moving tank and those that do find themselves easy prey for blast and template weapons. Sections of "wall" can also be detached to block movement from troublesome targets (like jump infantry or cavalry) as needed.
Though this example singles out Daemons, many similar units (Terminators, Lesser Daemons, Flayed Ones, Gargoyles, SM Assault Marines, Raptors, etc) deploy with similar goals and similar complications to face- so long as the unit in question is looking for assaults and isn't immune to mishaps, the tactic remains essentially valid. The fundamental point here is very simple: deep strike is too unreliable a mechanism to be used as a delivery system for assault units with any kind of regularity. Units- and armies- that do so open themselves up to exploitation by a castling strategy and will often find themselves forced to select sub-par sections of the map to arrive in and then face a long walk across the board to get to their targets.
The Second Threat: Deep Striking Shooters
Although less common than units that intend to assault, as a whole shooting units that deep strike tend to be much more dangerous, as they are allowed to act in the desired manner the turn they arrive. Most common of these threats is the deep striking Meltagun, which will try to drop in near a tank and vaporize it before the owner has a chance to do anything in response, effectively negating the Meltagun's short range. Similar tactics as against assault units will be in effect here, although in a reversed fashion.
(I should note that this strategy will have absolutely no effect on units that don't need to get close when DSing in order to shoot, such as models with Psycannons, Venoms/Raiders, etc; such units will be able to select a spot on the map at their leisure and care little for your ability to spread yourself across a quarter of the table- their range lets them arrive in a very safe fashion regardless of what you choose to do. Against such units other tactics can be applied, but little can be done to short out their effectiveness via these methods.)
Kirby has already described bubblewrapping in a number of his articles, and this forms the essence of the anti-shooting deep strike defense along with the above sort of general formation- it is, after all, usually vehicles we are trying to protect in such situations, as very few DSers can apply the kind of firepower necessary to completely wipe out an infantry squad in a single turn, bar extreme luck. Thus, the components of our formation quickly swap places in all of the above pictures, with the infantry forming "walls" around a central "keep" of vehicles. The priority here is, of course, to keep the enemy at least 6.1" away from all the tanks- and ideally further, if it can be managed.
At this point it is worth bringing up the most notorious of armies to use such tactics, the Blood Angels "Descent of Angels" or "Jumpers" list and its variants. Such armies will often be able to bring 12+ deep striking Meltaguns on a variety of platforms, a genuine threat to the tanks of almost any general, and their accurate DS makes a traditional castle formation somewhat shaky. Against such an army our setup is generally sound, but we will need to make our "traps" tighter (since the expected scatter values and unit sizes are both lower) and be more cautious about how big an area we think we can block off. BA will generally try to arrive 4" or 5" from your lines, netting them both guaranteed assaults and double-pen Melta shots unless an extreme scatter result is rolled, so any "traps" created or obstacles that you build your lines around should have safe zones of no more than 4" across, less if it borders on impassible terrain- unlike Daemons they can often afford to risk some of their units to give others more of a fighting chance, as they have access to Combat Squads and cheaper models in most cases.
Some rare units can also bring Multimeltas into play from deep strike, though in most cases these are "protected" deep strikes and will thus be covered more in the next section. Some others do exist, however, and against them you will find it much more difficult to deny them double penetration, though it can be done. Standard bubblewrap tactics will apply as always but will mostly just reduce the chances of their being able to arrive in close- if they pick a 8" safe scatter zone, they will often still be able to get a full-power shot off on you and will almost certainly be able to at least get a standard shot on the unit. You can realistically only expect to mitigate, not eliminate, such threats, but thankfully they are much rarer than the others and tend to come as part of armies that otherwise don't use deep striking as a general tactic, so attempting to castle against them is largely unnecessary.
Aside from flip-flopping the relative positions of infantry and vehicles, a shooting defense plays mostly like a melee defense, though of course your responses to their arrival will be radically different from those in the scenario above using Daemons.
The Third Threat: Protected Deep Strikes
Protected Deep Strikes are problematic because, unlike the previous discussions, they have partial immunity to mishaps (almost always as a result of enemy models and terrain.) This is by far the most common on the ubiquitous Drop Pod, but models like the Trygon and a few others possess it as well, allowing them to select their arrival point with impunity. Well, almost...
You see, one important thing to remember is that the Drop Pod et al do NOT give immunity to mishap results- they only reduce the scatter by enough to avoid impassible terrain and units. This has several key qualifiers: it doesn't protect them from scattering off the board (which isn't a terrain or unit), it won't ever increase scatter distance if they're placed poorly (such as in an initial position within 1" of such an obstacle) and it doesn't necessarily protect the contents (which we'll get to in a moment.)
The first point is relatively easy to take advantage of and most Drop Pod users are aware of it- board edges are just as dangerous to them as to anyone, so a force that hides near a table edge has a modicum of protection. Combined with pieces of impassible terrain this can leave some limited safe zones to pick from even against the protected deep striker.
The above represents a formation that is relatively safe from protected deep strikes; only two zones to the west and south can realistically have a unit enter near them.There are some more subtle tricks to fighting a Drop Pod, however. Note that the Drop Pod rules prevent it from suffering from a mishap by landing on enemy units but say nothing of the contents of the Drop Pod- and thus follow the normal transport rules for the situation. Since the Drop Pod's contents MUST disembark, we can note that units forced to disembark from a transport with insufficient room will place what models as can be placed in the open space (and more than 1" away from the enemy, of course) and then any remaining models are immediately destroyed- not to mention the remainder of the squad being unable to act that turn. Thus, a very canny general with a good ability to judge distances can leave "traps" in his lines even against Drop Pods, but do so in such a way that they are just large enough for the Pod itself (and maybe a couple models) to fit into, but not the entirety of the squad (and certainly not, say, a Dreadnought.) Such a tactic can be a bit risky, as a misjudgement in the size of the Pod itself can give them a perfect landing zone, but succeeding with such a formation is a glorious thing.
Protected deep strikers tend towards the shooting moreso than the assaulting side of things, though they exist in both flavors, and the generalities of either defense from the above sections can be applied as needed for either. For models like the Trygon the usefulness of such a formation can be limited unless there are large portions of the remainder of the army arriving by Deep Strike arriving alongside it, but it can still have some utility in giving the opponent limited options for where to place it (and thus allowing you to ensure your own firepower is able to get shots on it immediately on arrival.)
This also should not be taken as advice against full-on Drop Pod armies- such forces can usually be dealt with by a much simpler strategy of denying them targets, i.e. holding in reserve. While your own forces may come in piecemeal, such armies are almost never prepared to fight a battle at the long ranges you can engage them at (being able to pick your entry point as you are) and have invested heavily in being superior in close-in firefights that they prefer.
Conclusion
Deep Strike defense is part of the larger castling tactic that can have many other applications, from warding off Melta to ordaining the sequence of assaults that occur and more. Good use of it can cripple the Chaos Daemons army list and is a large part of why that codex is effectively nonviable in the 5th edition environment, even with the aid of its speedier units. I don't doubt that some folks will pop out of the woodwork and exclaim that they have had excellent success with their Daemons, won dozen of tournaments, etc, etc, even against this tactic and that it doesn't work and I'm stupid, etc; the truth is that while it may not be the entirety of the strategy against the army, it's a major starting point and leaves them fighting an uphill battle from turn 1, doubly so against mechanized armies of all kinds. Learning to build a good castle defense is part of learning good deployment, one of the most underrated and little-discussed tactics in the game and it can aid you against a number of different armies, even when it doesn't completely turn the tide of the game as with Daemons.
