I talk a lot about suppression fire. A lot. However, I rarely talk about what it goes hand in hand with which is anti-tank through close combat and one of my armies which I use operates off this assumption quite heavily. This do be Tyranids. Quickly, suppression fire is all about causing damage on your opponent's vehicles and not necessarily killing them. While through simple attrition of roles suppression fire can often be quite effective anti-tank against low AV tanks, suppression fire generally uses medium strength guns, high rate of fire and reliable hitting (i.e. Rifleman Dreadnought) to overcome a vehicle's armor value and potential cover. This will generally stop tanks shooting and quite often stop them moving. This is great for stopping incoming firepower against gunboats, battletanks or transports with guns whilst also stopping movement in general (a big part of mechanised lists). This second aspect of suppression fire however is also important for close combat anti-tank. Let's take a look at why this is so important.
Close combat as anti-tank isn't very reliable. Before we even get into needing to hit a tank the close combat unit has to get across the field. Some units like Terminators in Land Raiders, Seer Councils on Bikes, Bike units in general, beasts, etc. are quite capable of this but are needing at least two turns if not more to actually get to grip with an opponent's main army. Some armies in fact can delay that engagement to the 5th or even 6th turn with other tactics such as blocking and bubble-wrap. What this means is close combat units which are capable of damaging tanks in combat not only need to get across the board but fight their way through screening infantry units. This takes time and therefore relying on this can severely hamper your army against vehicles. Furthermore, once you get into combat a simple 6" move means your units are hitting on a 4+ whilst anything more than 6" and the unit is now hitting on 6's. Ouch. This doesn't seem very in the favor of close combat units for actually taking down tanks does it?
Here's where suppression fire comes in. Whilst combat units will still have to deal with getting into combat and the assorted troubles a unit may encounter whilst transversing the dangerous battlefields we play on, suppression fire allows combat units to more reliably damage units once they get into combat. If you combine good suppression firepower, anti-tank firepower (i.e. high strength guns, AP1, ability to easily penetrate armor, etc.), your own screening units/line-breakers and units which are pretty good in close combat against tanks, that ability to deal with tanks in combat suddenly becomes quite scary. The rest of the army is quite capable of dealing with the screening or blocking units and whilst they may be delayed by them, it's not like the TH/SS Terminators are stuck dealing with a 30-man blob of stubborn IG infantry. Backed up by suppression and anti-tank firepower, vehicles are also at risk and when the close combat anti-tank finally reaches them, they are more likely to be able to land a hit if suppression has been successful. However, even with suppression fire tanks can still screen each other or even throw themselves into your army's face which slows you up as you attempt to destroy the vehicle (in combat or shooting).
This is a huge list of requirements however (and we haven't even gotten into the characteristics for these types of units for them to be successful) so should always be a supplementary aspect of your army. Even the type of Tyranid army I run isn't relying on the combat prowess of units against tanks. Whilst it is quite high due to a number of factors, it's a late game strategy which I may work towards but do not necessarily need. Furthermore, assaulting tanks can be quite dangerous. Not only can a tank explosion hurt your men but your units are left clumped up as they have to get close to the tank hull and cannot make any sort of combat move after the assault has been issued (i.e. consolidation, pile-in, defender's react). Although this allows them to potentially whack the tank again the next player's turn, it also leaves the unit highly vulnerable to counter-attacks. So let's take a look then at what makes a good anti-tank close combat unit.
There are two things really, well three. Most units need a high number of attacks across the unit (even 10 Krak grenades from a Space Marine tactical squad can be scary). A high number of attacks helps minimise the requirement for suppression fire against moving vehicles as through simple weight of dice you are more likely to land a hit. Furthermore, high strength is required to penetrate armor reliably once a hit has been landed. This is a lot easier in 5th edition where attacks are always allocated against rear armor but some tanks like Land Raiders are always tough to crack and extra penetration rolls or high strength is required to crack them. The third aspect of effective close combat anti-tank is re-rolls. This isn't a necessity but allows the unit to not rely upon suppression fire to be somewhat effective. However, even with re-rolls hitting on 6s isn't so fantastic. Although some units can still deal with tanks in combat (such as Powerfist Sarges), they aren't really considered effective close combat anti-tank units (and remember, close combat anti-tank already isn't hyper-efficient). These considerations highlight units such as Monstrous creatuers (2D6 Pen, good number of attacks, can sometimes re-roll [hi Trygons] and high strength) and Beasts (medium strength, excellent number of attacks, fast and rending) as being effective anti-tank units in combat (again remembering their limitations). Even horde units like Orks or Gants who simply throw out 30+ S4 attacks are capable of combat suppression of tanks but all of these options still leave you vulnerable to counter-attacks.
Once again close combat anti-tank has serious issues but is an important part of 40k play. Being able to actually get to grips with tanks on the move by fighting through their screens and blocks is only half the problem. You then need to be able to hit and damage then and you're open to reprisal attacks (particularly low T/Sv units). However, if you have zero or minimal options for dealing with tanks in combat those tanks don't have to move as far or fast (or even at all) to defend themselves from close combat. Your opponent then isn't having to think on their feet and may force you to react to them. By having combat prowess capable of downing tanks backed up by suppression fire, both keeping their tanks still and moving their tanks forces your opponent into a potential lose/lose situation depending upon their army. In the end close combat anti-tank is excellent utility and should often be an integral part of an army but it should not be a defining factor.
