Anti-Tank brigade is usually underestimated for the following reasons:
- AT increases on Hard Attack
- most of battles are between mixed armies (soft and hard targets)
- aiming in battle is random, so your AT will fire on not only hard targets but on soft targets too, and its bonus could be neglected.
I don't want to calculate here complex chances and ration of hard and soft targets in enemy armies and conclude the rule, when AT is better than Art. I believe, there are some situations, when chances on the side of AT. I have quite strong argument here: armors usually live longer in the battle, so in the second part of the battle you are usually fight only with armors (if you army is not absolutely weak and didn't lose the battle in two hours). It's under discussion, of course and need math prove.
But I think I've found another arguments for AT.
Second Line of Defence
If you play for France or USSR you should know German tactics - Armored Breakthrough. Huge (mixed) army concentrate on a weakest direction, win the battle and penetrate your defence. Good defence strategy against breakthrough is levelled defence - when you have 2 or 3 lines of defence. Of course, 2nd and 3rd lines should not be such strong, as first. After all, they will be enforced by units of the 1st line after their retreat.
Come back to German breakthrough. After winning battle all or some units move to your province. They are rarely coming together. Usually, fastest units - armors, come first. Or even armors are the only units that moves into your province. And this is the moment of glory for your AT-brigades. Usual method to free the pocket is attack from all nearest provinces by all possible units and take your province back. Armors are hard to kill by infantry, so you need a high numerical advantage. Your infantry enters in such battles and step by step lose its organisation, even if wins. This leads to the situation, when your 1st-line units in nearest provinces become weaker and can't defend their position well.
So, the idea is simple. Use AT as attachment for 2nd- or 3rd-line units (i.e., in rear).
Good candidates for them are Infantry, Militia and Cavalry. But I'm sure, you should keep all your infantry in the first line. So, the choice is easy. Militia is cheap, while Cavalry is fast. Hard Attack for Mil-I is 0, for Cav-IV is 2 (like Inf-III or Mot-I)
The Weapon for Commandos
The next idea is not such useful and possibly rare to see, but still has its right to live.
If you use Paratroopers or Marines to capture provinces in opponent's deep rear, then you know, that your most danger enemy is Armor. Armor could fast move toward you and is very hard to kill. Usually, 1 commando could successfully defend province from a couple of infantry units, but even couple of commandos are hardly survive if attacked by one armor. So, it's reasonable to improve Par and Mar by AT-brigade.
Static Defence Bonus
While Static Defence is not favourable strategy for most of the player, it still has some reasons and its own flavour. And sometimes you have now other choice.
Chief of Army with Static Defence Doctrine gives the following bonuses:
* Land Fort construction bonus -10%
* Infantry construction bonus -5%
* Antitank brigade construction bonus -5%
* Infantry defensive combat modifier +5%
* Antitank brigade defensive combat modifier +5%
So, you see, that any unit with AT-brigade gets +5% combat effectiveness if is attacked. (Note, that Inf-AT still gets +5% bonus, not +10%. Note also, that this bonus increases overall combat effectiveness, not only unit defensiveness.)
So, the idea to get additional defensive bonus for non-infantry units: Militia, Commandos, Motorized, Cavalry, Garrisons. Combining with all defensive bonuses(terrain, forts, weather) you could get a huge advantage over attacker.
Also, cheap AT has additional discount and could be constructed almost for nothing.
AT vs Art
Easy calculations show me, that, alas, Early and Basic AT are weaker than their Art brothers even against Armors. Just because Art has its own Hard Attack and in the early game their HA values are very close. So, if you want to use AT tactics, you should use Improved AT('40) and later versions.
But anyway, AT is cheaper than Art, so its easy to build, especially with gearing bonus. Also, its easy to upgrade. Research of AT brunch is fast, so for Majors is not difficult.
Briefly:
Use AT against armors breakthrough as second line brigade.
Think about upgrading your Par and Mar units with AT, if they are going to make a raid in the enemy's rear.
Upgrade non-infantry units with AT to get Static Defence Doctrine bonus.
Use Improved AT or later.
