Anti-air Mechanic – How does it work?

[SEMPER FI]

May someone please explain how the anti-air mechanic for land, naval, and state level works? Is it similar to the air combat mechanic as explained on the HoI4 Wiki site (https://hoi4.paradoxwikis.com/Air_warfare)? I’ve looked through the forums, videos, and wiki site, but never presented a clear understanding. I understand about reducing air superiority, but how does it calculate for shooting down planes? Any help would be appreciated.

 

[Mccartney2006]

I've seen in other posts that it is mainly window dressing and that AA platforms, both fixed and mobile do nothing at all to fight of air attacks. I've seen this expressed by many and have seemingly witnessed it myself.

 

[currylambchop]

I've seen in other posts that it is mainly window dressing and that AA platforms, both fixed and mobile do nothing at all to fight of air attacks. I've seen this expressed by many and have seemingly witnessed it myself.

state AA will absolutely shred your enemy's strategic bombers.

 

[Denkt]

State AA reduce the damage strategic bombers do against your shared buildings (factories) as well as shooting down a few bombers which can add up given that a single bomber cost 60 ic (which is about the cost of equipping one infantry battalion). Researching radar and aa technology will make them more effective.

Division AA reduce air superiority effect based on their AA value as well as shooting down and reducing damage from aircrafts attacking the division in combat.

 

[Bunnytob]

Land: Reduction to enemy Air Superiority effects and a chance to shoot down enemy CAS (and TAC). Enough of them can also help with the air war, apparently - and if this is true I would also assume that it can shoot down strat bombers.
Naval: Somethin to do with shooting down planes. More rating = more chance. I've also seen a screen down a plane that isn't aiming for them before, but only in battles and not strikes. It's also very rare because DD1s have trash AA anyway.
State: Reduction to enemy Strat Bombing damage and a chance to shoot down said bombers. Also helps in the air war as it can shoot down fighters.

 

[Denkt]

Naval AA will likely be changed in the expansion to be more like land based AA with damage reduction against naval bombers.

 

[SEMPER FI]

All,

I appreciate everyone's response and input.

 

[gagenater]

If you want to see how good state level and division level AA is, do a solo run as Czech, refuse the sudetenland ultimatum and fight germany. Do it once and rely on your air force for air superiority, and do it again with state level AA in key areas, and/or division AA. without the AA, the german bombers rather rapidly junk your forts, and leave you unable to effectively defend. With the AA, your guys are snug as a bug in a rug behind their fortresses, while german planes fall out of the sky.

 

[Secret Master]

You guys have far more faith in static AA than I do. I don't deny that it has value, but now that you can target specific types of buildings, it's value is primarily in terms of time and effort. With enough static AA to matter, it means that the STRs have to bomb the AA first before hitting more valuable targets. But the static AA can be demolished, and then the STRs can hit the things you want. Or the defender has to put so much effort into repairing the static AA that they are spending CIC on the AA repairs and not doing things like building factories or MIC. And to get enough static AA to matter, you have to actually build it in the first place and research relevant techs that make it better. The starting static AA in the game for every country that has some is too small to matter.

Here's some examples:

First example: 600 1940 STRs versus the maximum number of AA guns in northern France. The bombers are halfway through the Strategic Destruction doctrine tree, and the French have 1940 AA techs (to improve their AA guns).

After a month, the AA guns bagged 22 STRs, but the AA guns are seriously damaged. Around 40% of the AA guns are out of action. In the next month of fighting, the French have to decide whether to continue repairing the AA guns (which will not be easy) or just accept their damage and let auto-repair deal with it.

But for the bombers, in the next month, they can just swap targets and start attacking more valuable targets. And while losing 22 STRs in the first month is harsh, that number goes down in the next month as the AA guns do less damage. And if the STRs bomb 17 buildings the next month, but take out 17 CIC or 17 synthetic plants, the defender has to make tough choices on what to repair.

There's also the question about whether the defender can afford that many AA in the first place. For every 3 static AA you build, you could build an MIC. So, if France built 42 AA guns to full out the states in the air region, that's 14 MIC you didn't build. Then again, 600 STRs aren't exactly cheap.


What about higher tech planes and AA?

Running 600 1944 STRs with the Strategic Destruction tree completely filled versus 50 static AA with max RADAR and max AA gun techs.

Under these conditions, the bombers do slightly more damage with the defending AA guns claiming the same number of bombers. Again, though, in the next month, the number of bombers killed will decline because the AA guns are out of commission, putting the defender in the same position as in our last test. Either they keep trying to repair the AA guns, meaning that their CIC isn't building new IC, or they let auto-repair do it, but then the STRs hit other, more valuable targets. And even repairing the AA guns will not make up for the damage being done. Partially damaged buildings do not function, so having a bunch of partially damaged AA guns are not shooting at anything.

You should also consider the following issue: None of the STRs used in these tests had any XP applied, and the bombers had no ministers affecting them. The 1944 STRs, if you apply XP to them, can increase their strategic attack from 60 to 75. The 1940 STR can go from 45 strategic attack to 56. That represents a substantial increase in their bombing capability if someone were so inclined.

Static AA has real value, but it's value is in buying the defender time and leeway to get an air defense in place. It's not going to save the defender by itself in the long run, though.

 

[Denkt]

Is AA affected by radars (the improvement not the technologies)?

Anyway the point of AA is like forts not to defend by themself but act as a defence multiplier and make offensive operations too expensive for the enemy so you can eventually turn the tide.

Even with interceptors you wont probably reduce a serious strategic bombing offensive to zero effectiveness and even if the interceptors are cost effective the damage done to you may still make it worthwhile. With AA you can reduce the effectiveness even further and that could be very important as it pretty much is a multiplier to the reduction caused by the interceptors.

 

[Secret Master]

Is AA affected by radars (the improvement not the technologies)?

I don't think the presence of actual RADAR in the region affects AA. The last time I tested it, it was only the tech that seemed to matter.

Even with interceptors you wont probably reduce a serious strategic bombing offensive to zero effectiveness

You can, but it's a lot of work. And there is a point where enough STRs in an air region essentially wipe out the airfields fast enough to shut down the opposing air force.

But leaving aside situations where 10,000 STRs are hitting one air region, investing in some AA defense to supplement fighters is worthwhile if you see enough enemy air power, or you need help while your factories on fighters wind up to better production. Only a fool would trust AA to resist an serious bombing campaign on its own, but it can help.

 

[seattle]

There's always the matter of "opportunity costs", i.e. what's the investment alternative?

If you're swimming in CIC and don't know what to do with it while your cognitive capabilities are hampered severely cause you're in the middle of Barbarossa... just plastering AA all over the place might be a great idea.

Generally I like every option that is a one-time investment and provides utility henceforth for free. Forts, radar, AA, CIC are such investments.

I'd guess that for Germany max AA makes sense in Western Europe and particularly Germany itself.
Max radar there as well + fighters. Great combo.

 

[everburn]

I don't think the presence of actual RADAR in the region affects AA. The last time I tested it, it was only the tech that seemed to matter.
You can, but it's a lot of work. And there is a point where enough STRs in an air region essentially wipe out the airfields fast enough to shut down the opposing air force.
But leaving aside situations where 10,000 STRs are hitting one air region, investing in some AA defense to supplement fighters is worthwhile if you see enough enemy air power, or you need help while your factories on fighters wind up to better production. Only a fool would trust AA to resist an serious bombing campaign on its own, but it can help.

Cost can't be compared that easily, and I don't really agree with your numbers ( this time).

If you really mean the cost this way actually, you could build even more MIC for each 3 AA, as MIC take infrastructure bonus, meanwhile AA doesn't.

But my point it's not this, the point is :

Provincial AA it's GOD when you need to defend ( it's not like you can attack with tho)

In this case you are using 600 STR to bomb a province, to prove a point, but in my own opinion, you are proving the only point that you are not proving the point in the correct way.

You are leaving AA to defend Alone. Actually, the main role of AA it's reducing incoming damage not destroying STR. They also destroy STR, but it's not their mainrole. On my own eyes, in this case, it's like attacking infantry with tank destroyers, or defending with forts without units inside.. Not really efficient.

Provincial AA reduces 60% of the incoming damage at maximum, with dispersed industries and improved AA the value can reach 90%. Radar can increase hit chance ( and so allow provincial AA to do more damage).

AA prevents the damage if there is not enough damage reduction from the interception of fighters and heavy fighters and then secondary they also destroy STR. As even the distruction of a single MIC or a civilian factory, or even a Synthetic Plant, could make a LOT more of economic damage, than loosing some heavy bombers for it.

We already know that in the game, you are never going to have 600 STR without giving up something else somewhere else. The cost of an STR II is 62, multiplying that number for the size of that wing means 37200. You could just have 1240 Heavy Fighter II ( a single heavy fighter cost 30) or 1430 fighter II ( a single fighter II cost 27). There is also no comparison if you try STR vs Heavy Fighters in the same numbers, as they are not worth they same.

But talking about this case, if we consider an IC budget of 37200 worth of STR, I could "pay" one level of radar (3375), 5 level of AA (2500*5) for a cost of 15875 and the remaining 21325 converted or 710 heavy fighter II or 789 fighter II and easily give the 600 STR an "hard lesson"

In this case you would have just made the defense of a province of like infantry that needs to cross a river attacking into a mountain province, against a level 10 fort with heavy tank/mechanized and SPART inside.

So if you know where your enemies are going to attack, and you prepare the correct defense you will trade way more efficiently. That's all

 

[seattle]

@everburn
That's what I meant with opportunity costs.

What better investment alternative does the US have? 300 grounds divs? Not useful --> strat bombing is a great choice.

Likewise for Germany? No, cause Germany better spends her IC elsewhere. You don't win Barbarossa with strat bombing. You need to put boots on the ground.
--> strat bombing not viable for Germany

What about defending against strat bombing then?
It's all nice and dandy to show the crippling effect of mass strat bombing and the inadequacy of AA to prevent it.

But what is the best defence then @Secret Master ?
Obviously you can't just take the pounding (gotta control myself here not to make a joke).
I would say that a combined defenceis the best strategy:
- AA
- adding flak to garrisons in the bombed regions
- max radar
- fighters with pimped guns

Proving that AA alone doesn't work, doesn't prove that AA as part of the defence doesn't work. I love the new buffs to static AA in the AA tech branch, one that I would research anyways cause I use it in divisions.

#only a fool...
A fool or someone playing HoI2 where lvl 10 AA was all tge airforce Germany needed.

 

[Alex_brunius]

Cost can't be compared that easily, and I don't really agree with your numbers ( this time).

...

We already know that in the game, you are never going to have 600 STR without giving up something else somewhere else. The cost of an STR II is 62, multiplying that number for the size of that wing means 37200. You could just have 1240 Heavy Fighter II ( a single heavy fighter cost 30) or 1430 fighter II ( a single fighter II cost 27). There is also no comparison if you try STR vs Heavy Fighters in the same numbers, as they are not worth they same.

But talking about this case, if we consider an IC budget of 37200 worth of STR, I could "pay" one level of radar (3375), 5 level of AA (2500*5) for a cost of 15875 and the remaining 21325 converted or 710 heavy fighter II or 789 fighter II and easily give the 600 STR an "hard lesson"

So in the end you do agree with SM that AA alone can't do the job but you also need fighters...

Your also missing a key point when the cost you list is only enough to defend a single state, but the bombers are going to be hitting all 5 - 10 states in the entire airzone. So the actual cost of AA is much higher then what you hint at...

Even more so when the bombers can move to a new zone in a week but once AA is built it can't be moved.

 

[SEMPER FI]

I appreciate everyone's input about the cost/benefits of AA. However, does anyone actually know how the anti-air mechanic works? I mean the specific formulas the games uses to determine if a plane is shot down. As I mentioned before, the HoI4 Wiki site (https://hoi4.paradoxwikis.com/Air_warfare) gives a great explanation of the air combat mechanic. I interested in this type of detail.

 

[Alex_brunius]

I appreciate everyone's input about the cost/benefits of AA. However, does anyone actually know how the anti-air mechanic works? I mean the specific formulas the games uses to determine if a plane is shot down. As I mentioned before, the HoI4 Wiki site (https://hoi4.paradoxwikis.com/Air_warfare) gives a great explanation of the air combat mechanic. I interested in this type of detail.

AFAIK Most AA is linear, so double AA value = twice as many planes shot down.

 

[SEMPER FI]

AFAIK Most AA is linear, so double AA value = twice as many planes shot down.

Thanks...

 

[Secret Master]

You are leaving AA to defend Alone.

Well, I'm responding to the idea in this thread that AA will stop bombers. For example, this post:

state AA will absolutely shred your enemy's strategic bombers.

It won't. You can't rely on AA to do the job itself. You need fighters to help, as I say here:

Static AA has real value, but it's value is in buying the defender time and leeway to get an air defense in place. It's not going to save the defender by itself in the long run, though.

Obviously you can't just take the pounding (gotta control myself here not to make a joke).
I would say that a combined defenceis the best strategy:
- AA
- adding flak to garrisons in the bombed regions
- max radar
- fighters with pimped guns

If by FlaK garrisons, you mean divisions with AA, those won't affect STRs.

Regarding fighters:

In vanilla, there is a strange paradox with fighters. On the surface, it appears that you should build light fighters to claim the skies, with a small reserve of heavy fighters to counter strategic bombers. This doesn't actually work as well as you think in vanilla, for a whole list of reasons. The short version is that even when set to intercept, the heavy fighters get stuck in dogfights with escorting light fighters alongside their own light fighters. And in vanilla, heavy fighters are cost inefficient against any kind of light fighter resistance (with some small exceptions at the 1936 tech level). Even worse, design companies either buff lights or heavies, but not both. So, if the enemy bothers to escort its bombers, the heavy fighters you are putting on zerstorer duty are, essentially, getting wasted in air to air combats to which they aren't suited. (Seriously, I tried 20 different wing compositions in an attempt to find the sweet spot where a percentage of heavy fighters working along side light fighters would be IC efficient against bombers. I didn't find a single composition that worked.)

So, the answer seems to be light fighters with gun upgrades. Light fighters with no gun upgrades perform sub-par against equal tier STRs; the STRs claim a significant number of fighters as kills. It's better than nothing, mind you, and let's not discount bomber disruption, but light fighters in their base configuration are not the answer to STRs over the long term. So, upgrade guns? But the problem you get into here is that every level of guns you put on your light fighters hurts their dog-fighting ability. If you turn your light fighters into zerstorers, they will have no problem killing bombers, but now they suck against enemy fighters like their heavy fighter brethren.

The solution I have come up with is the +5/+1 design. Ignore heavy fighters, run light fighter design company, run Operational Integrity to get more agility, and the fighters get +5 engines, +1 guns. The extra guns are not enough to kill their dog-fighting performance, but it does help them shoot down TACs and STRs. It's the best compromise you can get in vanilla.

 

[bitmode]

I appreciate everyone's input about the cost/benefits of AA. However, does anyone actually know how the anti-air mechanic works? I mean the specific formulas the games uses to determine if a plane is shot down. As I mentioned before, the HoI4 Wiki site (https://hoi4.paradoxwikis.com/Air_warfare) gives a great explanation of the air combat mechanic. I interested in this type of detail.

According to the code it looks (very) roughly like this:

• airDefenseRatio = 0...100% (scaling linearly with state's static AA)
• hitChance = airDefenseRatio * (1 + static_anti_air_hit_chance_factor) * ANTI_AIR_PLANE_DAMAGE_CHANCE
• dieRoll = random number between 0 and 1
• abort if hitChance < dieRoll
• airWingDefense = the wing's air_defence stat, modified by the ace, the country's air_defence_factor, strategic_bomber_defence_factor where applicable respectively
• planesCount = number of planes taking part in attack; seemingly air wing size reduced by mission efficiency
• dmgDealt = planesCount * (1 + static_anti_air_damage_factor) * ANTI_AIR_PLANE_DAMAGE_FACTOR * airDefenseRatio * dieRoll / hitChance / airWingDefense
• edit: substituting hitChance, this would be: planesCount * (1 + static_anti_air_damage_factor) * ANTI_AIR_PLANE_DAMAGE_FACTOR * dieRoll / (1 + static_anti_air_hit_chance_factor) / ANTI_AIR_PLANE_DAMAGE_CHANCE / airWingDefense, which seems... weird
• the resulting damage gets rounded down but is at least 1 and is then dealt as number of planes destroyed to the air wing

Example:

• targeted country has level 4 radar researched (the first level that gives +20% static AA hit chance)
• targeted country has AA guns 2 researched (+10% static AA damage)
• the targeted state has level 5 state AA
• 100 unmodified TAC1 (air_defence 18) without an ace do strat bombing with 100% efficiency
• die rolls 0.10

The AAs hit chance is 100% * 120% * 10% = 12%. This results in a hit. Damage dealt is 100 * 110% * 80% * 100% * 0.1 / 12% / 18 = 4.07, i.e. 4 TACs get destroyed.