Reconnaissance (REC): A recon company provides a speed bonus on most terrain and a reconnaissance points bonus to the commander that increases the chance to counter the tactic chosen by the enemy for a day of combat. Engineers also increase division defense and soft attack, but not as much as an infantry battalion. Lastly, they provide a constant attack bonus to amphibious (naval invasions), which stacks with Marines bonuses. Upgrading engineers increases the entrenchment bonus and adds additional attack and defense bonuses in forts (II), rivers (III) and urban environments (IV). They also provide an entrenchment bonus on top of that. They provide a constant defense bonus in forest, jungle, hills, marsh, rivers, and forts. If you only need protecting your army from air attacks, just produce AA, although it can't effect enemy division, but it is cheap and unbreakable from air.Д®ngineers (ENG): Engineers provide a movement bonus in forest, jungle, marsh, and rivers. It's strange, since it neither accords with history, nor meets the formula about AA in navy. AA with 1936 equipments can shot down up to 5% attack planes per 8 hours. Interestingly, AA are more efficient than fighters on shooting down planes(ver 1.10).Having towed or self-propelled AA in a division reduces the malus that enemy air superiority inflicts.AA does not require Tungsten to make, so it may be a budget AT option for minor countries. However, self-propelled AA doesn't have anywhere near as much anti-armor capability. For example, the tier 2 towed AA has enough Piercing to negate the Armor value of tier 1 medium tanks. It should be noted that towed AA units also have half-decent anti-armor capability.Editor's Note: The video where the Devs said they can shoot down fighters is the 'Together for Victory feature stream' on Youtube.Of course, if you have no fighters, putting AA in every division on the front line may be your only option. At least as of version 1.3, the Devs have reported that attached AA can shoot down fighters, but it takes a lot of it (the example in the video showed multiple line battalions, not just a lone support company).They do nothing against strategic bombers (they fly too high), so adding AA to garrisons will not help protect industry.Towed and self-propelled Anti-Air will only fire at enemy planes attacking that division or other divisions that take part in the same battle. Support Companies In-DepthДЄnti-Air (AA): AA will primarily help protect against tactical bombers and CAS attacking a battle that the division is participating in, allowing multiple divisions in the same battle to pool their AA fire. Note that percentage bonuses are multiplied, not added. +10% Speed roughly, depending on recon type and terrain type. If you spot a mistake then you are welcome to fix it.

Hoi4 best support companies