Blocking is commonly associated with vehicle. Specifically sending a fast vehicle such as a Land Speeder or Piranha with a melta weapon forward and planting it in the way of a big, bad, scary tank like a Land Raider. This is blocking at its simplest and there are many variations and extensions of this tactic - all involving vehicles. Today we are going to discuss blocking with infantry and the importance it has in objective based games.
When infantry block there are a couple things you need to remember. First, other infantry can ONLY come within 1" of you during the assault phase. They can come within that 1" bubble even if they are not assaulting you so those 2" coherency gaps you leave? Well they let infantry models right on through during the assault phase. Otherwise infantry block other infantry very well during the movement phase and if spaced correctly, can stop assaulting units from getting through beyond the blocking line. Secondly, only tanks can tank shock and meltaguns are scary for tanks tank shocking. Vehicles like Piranhas, Land Speeders, Trukks or Raiders can zoom a vast distance to get to specific points on the table (objectives) but cannot actually tank shock into a unit. This is why certain upgrades such as Shock Prows and Reinforced Rams are very important and why infantry blocking is so important, too. You hear a lot about how cheesy fast units at the end of the game are - learn to block. Shunting Interceptors and 24" moving Land Speeders or 36" moving Reavers are no longer a problem if your infantry are appropriately arrayed. Furthermore, tanks which can tank shock obviously don't want to tank shock through meltaguns or will only do so in the direst of circumstances. Placement of these guns is therefore very important as it can deter your opponent from specific avenues of tank shocking.
With these two key principles under our belts, let's look at how infantry can block and their most primary function outside of bubble-wrapping. This is protecting objectives and from here (plus the concept of bubble-wrap) you should be able to extrapolate these techniques to other aspects of gameplay. So, to protect an objective you need to keep your opponent more than 3" away from it. You only need one model within those 3" but you don't want to give your opponent the ability to pull your squad away from the objective nor be able to land inside your protective ring. An appropriate setup therefore might look like this.
There are no 1" gaps between the models for infantry models to squeeze through during assaults, all the anti-tank guns which could potentially death or glory are well outside the 3" mark and all but a few infantry have their bases edged outside of the 3" bubble and thus if engaged in a combat are going to keep the opposing unit out of 3" whilst maintaining control of the objective. The only way for your opponent to now be able to access the objective is through a tank shock or extreme shooting to open holes in the line. You can't do much about the shooting other than making sure you're in cover but you can do something about the tank shocks in making it a very risky move. At the end of the game these risky moves will be made though if the game can be won or lost on them so you must ensure the move is as risky as possible to improve your chances of holding the objective.
The placement of the anti-vehicle weapons, specifically meltaguns, is obviously very important to this and very situational. If you're against a non-tank army it's not that big a deal and using an infantry block as an actual blocking mechanism is fine. When there are tanks on the board which can tank shock though, you need to deploy these sorts of weapons carefully. In the above example we are protecting the front and sides of the objective but not the rear. A tank could come along like so...
...and wham, bam, thank you ma'am, the objective is now contested with no feasible death or glory attempts possible. Placement of such weapons is therefore dependent upon where your opponent's vehicles are. If there are none in the front arc of the unit, don't place them in the front arc! Where they are located is also quite important for if they are far away, they can generate more angle and be able to avoid your weapons depending upon the size of the squad. This can be seen in the above example. If the weapons are deployed further away however, you reduce the amount of room the vehicle has to go around said model with the weapon. For example...
by moving the Missile Launcher further away (and shifting the position of the meltagun up top), the Rhino has to either tank shock through a Missile Launcher or meltagun or cannot physically contest the objective (though still clips a model so they have an Ld check). The problem of course becomes when there are multiple vehicles around, not every unit has multiple anti-tank weapons with which to death or glory and moving heavy weapons to stop such moves isn't always the best move. This is where bringing other tanks to play can be a great benefit.
By using a couple of tanks you can use 'normal' blocking techniques to protect an objective from specific avenues. The opponent can still ram or potentially explode the vehicles so you need to ensure the opponent still cannot move into the 3" zone (they could potentially in this picture - naughty me). However, this is still another layer of defense and allows you to concentrate weapons useful for death or glory on the opposite flanks and reduces the impact tanks can make with tank shocks and objective contesting. You can further this by of course having tanks with Troops inside actually within the 3" of the objective but then that's moving back into primary tank blocking.
Conclusion
Tanks and mech armies will always have an advantage in objective games, particularly when going second, against foot lists because of this. By being able to intelligently block with your infantry against other infantry, you force the opponent to use this advantage which you can attempt to prepare for. Tanks still have an advantage as you have to pass leadership checks (often multiple times) and can simply move infantry out of the way but they can be vulnerable when doing so (terrain, death or glory 'free hits', becoming surrounded, etc.) and to effectively use infantry blocks, specifically to hold objectives, you need to take advantage of these vulnerabilities. Use your weapons which can death or glory wisely to force the tank away from the 3" bubble, force the tank through terrain, etc. When tanks are not in the equation the infantry units themselves are an effective blocking force and should not be underestimated. They are very effective at keeping normal vehicles and other infantry away just be sure you don't leave 1" gaps for the opponent to slip through during assault.
When you combine both infantry and vehicle blocking, opponents can find it very difficult to move through your lines, flank your or access objectives and are forced to rely on shooting/combat. Take away movement options from your opponent or make those options risky and you'll find yourself having an advantage over your opponent.
