Deployment - a subject that could stretch on for forty thousand hours of chatbawks debate, and is different depending which army you play, what build you run, and which particular way you hold your mouth when you set your models up. This article is to explain the basics of army deployment, without specifics to a particular army. So before we go any further, lets look at the deployment phase. This is a key part of how you intend to use your army, and what you do in the deployment phase will dictate what you and your opponent attempt to do throughout the game. A midfield/assault army will deploy as closely as possible to you, and try to herd you into a corner. A mobile army (when played well) will see where you deploy, then move where you are not. There are several different basic methods of deploying, and not all of them are good.
Pitched Battle Line - The Newb Crusher
This is where we all start. You get a starter set, or your mates army, and you deploy parallel to your board edge. AWSUM! MY ARMY IS GO! You may give little or no thought to what actually goes where, but that's how they do it in the White Dwarf batreps right?
Pitched battle line is generally (I can't really think of any exceptions) a bad idea. If your going second as a mobile or mechanised army, it may work for you, as you can relocate yourself into a sword thrust to smash apart the enemies lines. If your horde orks, or nids, you are probably set up in a pitched battle line because well, you need all the deployment zone you can get.
Strengths - It's efficient on space? Great for photo ops? I don't think there really is any.
Weaknesses - If you deploy second, it allows your opponent to focus on the part of your army that is either a) in range or b) the biggest threat, and remove it from the board. They can then systematically move along your battle line, taking out units which will now lack support on one flank. Your remaining units are now further away, either a) preventing them from being in range to retaliate or b) not being fast enough to get into range to do some damage.
Refused Flank - The wargamer's bread and butter
The most common answer at tournaments. Used particularly by gunline armies, or armies with high mobility (ie Eldar, Tau, Guard, etc) this is the easiest way to maximise the amount of shooting you get at your opponent, before he gets close. When used correctly, spells certain doom for most assault armies. Not to be confused with the castle, although one can castle into a refused flank. Basically you pick one die of the board, and deploy as close to that short table edge as possible. Best used if your deploying second, but is totally viable - it may force your opponent to clump up if he wants to get close to you, and that can be great if your packing Str 10 AP 4 barrages of death, and the like.
Strengths - Focused deployment is focused strength. Keeping maximum distance between you and your opponent is the difference between them getting a turn 2 assault off (quite possible for Dark Eldar or jump marines, or TWC, or Fiend of Slan... etc) and you getting to turn 3 without your key shooty units engaged. That extra turn of shooting makes/breaks gunline armies, so you should strive to ensure you get it.
Weaknesses - You are all in once place. Its very easy for a mobile army to pin you in that corner, and take you to pieces. Also, any sort of barrage large blasts can really ruin your day. Also, if you've refused hard, and your bunched up, assault armies may be able to get off a multi-unit charge, which will probably not end well for you, if your gunline.
The Pincer/Split Deployment - LOL DEEPSTRIKERS!
That pretty much sums it up. Want to REALLY ruin your Jumper BA/Daemons opponents day? Take everything you have, split it down the middle, and put it on opposite sides of the table. Force him to pick one side. You will likely lose that side, but you will take a lot of them down while it occurs. Now laugh maniacally as they jump/run and across the full 5' between you and them, guns blazing all the while. Also can be effective at splitting up mechanised forces, peeling little metal coffins apart and removing their support from one another can work at times. Basically, split your army as above, and force your opponent to make hard choices about what he needs to kill. If the side of the pincer that he chooses is copping a pounding, to crazy things like going to ground, sacrificing razorbacks as shield walls, whatever you have to do to keep his attention focused on that flank. Minimal retaliation means your other flank should get to have a field day.
Strengths - Very effective vs armies that cannot redeploy efficiently. Has the same bonuses as a refused flank, by putting max distance between them and some of your army, but forces your opponent to make choices.
Weaknesses - they don't say "Divide and Conquer" all the time in those war movies for nothing. If your facing something that can either a) out range you or b) outmaneuver you, this isn't the tactic for you. They will remain in control, either by picking you apart at range, or simply moving rapidly from one flank to the other, eliminating threats.
That's pretty much it for now. I realise that there is many variations on basic deployment, and how these basics vary when used by a midfield
As always, comments welcomed, if you feel I've missed anything specific, or you'd like more info on an individual set up, let me know.
Thanks, SneakyDan