I've seen Expert AI touted a fair bit as a way of improving the AI, specifically when playing a historical game, and I recently did a thread analysing the vanilla AI, focusing on the day of the Barbarossa invasion.
Now, before I get into the specifics, some caveats. This was only a single game played, and it was on the latest version of the game which Expert AI has not yet been updated to support. Hopefully people find the information useful all the same.
Settings and DLCs:
Expert AI has a ton of settings - do you want the AI to play optimally, or follow historical templates? Do you want Japan to win the Sino-Japanese war, or not? Do you want the Axis to invade Norway? Etc etc etc. I left it on the default "challenging" settings, except that I changed "Sino-Japanese War: Favour Japan" to "Sino-Japanese War: Favour China", since China did win that war and I want a historical feel. It's not particularly important to Barbarossa though.
I have most HoI4 DLCs aside from cosmetic ones and Battle For The Bosporus. Most applicably, I have No Step Back.
Timeline:
The game progressed mostly historically, with the Spanish Civil War ending a few months earlier than reality, much better than the year-or-so early vanilla had.
I did notice some weirdness once WW2 started, with a French fast division barrelling into South Germany unsupported, making it all the way to Regensburg before being surrounded and destroyed. Germany then went straight through the Maginot line and Italy joined the war before even Poland fell. As a result, France fell before Germany even went after Belgium and the Netherlands.
I also saw the UK declare war on Iraq in July 1941. I wonder how much of this can be explained by the mod being set to "challenging" instead of "historical".
Now let's look at the USSR and Germany's situation on the day of Barbarossa in detail:
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Soviet Army:
254 divisions total, comprising 2.8 million manpower, 5580 AA guns, 4450 AT guns, 2410 artillery pieces, 240000 infantry gear, 4010 trucks, 14600 support gear, 1530 light tanks, and 1040 heavy tanks. The most common division type is the 186 infantry divisions (10 infantry battalions, one line AA battalion, support artillery, engineers, AT, logistics and maintenance), with four heavy tank divisions (14 heavy tank battalions, 7 motorised, with support engineers), and a lot of trash divisions (22 divisions of 4 cavalry battalions, 18 divisions of 6 infantry battalions with military police) that they started with.
This is a larger army than the vanilla AI built, and also a lot more homogenous, with the vast majority being of one template where the vanilla AI is a bit all over the place. The vanilla AI leans heavily on line artillery and light tanks, while the Expert AI goes heavily into support companies and a few very large heavy tank divisions.
98 of the Soviet divisions are on the German border, 92 of them being infantry, 4 mountaineers, and 2 cavalry. Notably there are no tanks on the German border. This is kind of funny given that the German AI has gone to the trouble not only to put AT guns in all its divisions, but also to research AT gun tech ahead of time. Manpower-wise, the Expert AI has very slightly more manpower on the front with Germany, but probably somewhat less power due to having much fewer artillery and tanks.
So where are the enormous, expensive Soviet tank divisions? They're all on the border with Romania. Given that Romania will join the war soon, that's not a disaster. I'd have put them on the border with Germany, though. The Romanian border is well-guarded, with 38 infantry divisions, the entire heavy tank strength of the USSR, and a half dozen trash cavalry and light tank divisions.
The Hungarian border has 15 infantry divisions, and some trash NKVD and light tank divisions.
15 divisions, mostly trash, are on the Japan front. Not as bad as the vanilla AI, which had 29. What is as bad as the vanilla AI is the guards for the interior of the USSR, with over 50 divisions guarding various unimportant points, including the traditional 3 divisions in Dudinka and garrisons for islands between the US and USSR.
I'm not sure what control mods can have over how the AI distributes its divisions, this looks pretty similar to how the vanilla AI did things.
Soviet Stockpiles:
3.44 million manpower
964 AA
-745 AT
480 art
9000 infantry gear
-313 truck
-487 support gear
-563 light tanks
-1100 heavy tanks
128 train
-36 strat
80 transport planes
121 fighters
90 nav
-73 tac
423 convoy
Notable here is that Expert AI has solved the Soviet manpower crisis - in vanilla they only had 200,000 manpower left. There's also not the huge stockpile of infantry gear vanilla AI had, probably because they're training another 60 infantry divisions. They are significantly undersupplied in the heavy tank department - their divisions are at about half strength there.
Soviet Air Forces:
These are generally much larger than in vanilla, with 6000 fighters to vanilla's 1000, but no CAS where vanilla had a couple of thousand.
This is a big improvement over vanilla - there's no point having CAS without enough fighters to defend them, while fighters will do just fine without CAS.
Miscellaneous Thoughts:
Severe heavy tank shortage - basically four divisions are deployed when there are only enough tanks for two. All of those divisions are on the Romanian border - not great, not terrible.
The heavy tank division probably doesn't need to be accompanied with motorised infantry - the tanks only go 4.7 kph. Maybe replace the motorised with leg infantry and give the tanks worse engines if they're going to be this slow?
Naval production's a bit crap - three lines of early destroyers when 1936 destroyers are available.
-84 aluminium shortage! They are importing from Switzerland, Manchukuo, Sinkiang, Malaya and Sweden, but the US, UK, and even Vichy France are available and not being used.
-----
German Army:
147 divisions total, comprising 2.5 million manpower, 7190 AA guns, 3020 AT guns, 17400 artillery pieces, 185000 infantry gear, 5250 trucks, 13600 support gear, 2700 medium tanks, 432 medium self-propelled AA guns, 532 medium self-propelled artillery, and 243 medium tank destroyers. The army is pretty homogenous, with 120 divisions being 14 infantry battalions, 4 artillery battalions, 2 AA gun battalions, with support engineers, AT, logistics, hospitals and maintenance. The six tank divisions have 9 medium tank battalions, 2 medium self-propelled artillery battalions, 2 medium self-propelled AA gun battalions, 1 medium tank destroyer, and 6 motorised battalions, with support engineers, AT, logistics and maintenance battalions.
This is a similarly-sized army to what the vanilla AI built, but concentrated into far fewer divisions. The focus on medium tanks and line artillery is still in place.
The Expert AI has done a fair bit better than the vanilla AI when it comes to positioning its divisions. They've managed to get 86 of their divisions onto the Soviet border, 58% of the army, compared to vanilla's 29%.
Where the Expert AI has not improved on vanilla is its fixation with Italian East Africa - 23 divisions are sailing between Europe and Italian East Africa, including two of the six tank divisions.
Positioning of tank divisions is better than vanilla, but whether this is just luck, I'm not sure. Three out of six tank divisions are on the Soviet border, with two at sea off Africa, and one guarding the Norwegian coast.
German Stockpiles:
500000 manpower
1400 AA
-42 AT
-106 art
35000 infantry gear
1700 truck
341 support gear
1100 light tank
-4 medium tank
734 train
714 medium SPAA
-144 medium SPART
-79 marm
55 transport planes
169 fighters
13 CAS
100 Naval Bombers
-76 TAC
824 convoy
These are better than vanilla, which had a ton of surplus infantry gear and artillery, with big truck and tank deficits.
German Air Forces:
Again, far more fighters than vanilla - 5000 vs 1000. There's also a bigger focus on naval bombers, with 400 versus the 100 of vanilla. CAS numbers are similar, with 1000 on both AI versions, and vanilla has 700 tactical and 200 strategic bombers that Expert AI does not.
I'd definitely take the Expert AI version of this over the vanilla AI one - fighters are king.
Miscellaneous Thoughts:
Logistics are pretty good - there are a thousand or so light tanks doing nothing in the stockpile, could be worth using those until they fall apart.
Research is about right. Rubber refining has been researched which is allowing a ton of plane production - this is a big improvement over vanilla. The crazy focus on armoured car research is gone. AT guns have been researched ahead of time, which is kind of funny given that the Soviet AI hasn't managed to bring a tank to the German border.
Tanks aren't as slow as the Soviet ones which are barely faster than walking, but they're only doing 6.7 kph.
-----
Factory counts, (compared to vanilla):
This is a significant improvement over the vanilla AI - it's generally accepted that military factories are king, especially when it comes to Barbarossa, and all three factions have many more military factories as well as more civilian factories to boot.
The Allies have considerably fewer dockyards in Expert AI, but given that they're still comfortably ahead at sea, they're not even using all the dockyards they have, and the ones they are using are building bad ships (early destroyers when they have 1936 designs, 1936 cruisers when they have 1940 designs), I think this is a good sacrifice for them to make.
A lot of these extra military factories are going into fighter production - this is generally a good thing and will make the AI much more threatening and harder to dominate with air power. There is an issue where the USSR has far too little aluminium and isn't trading for enough, but on the whole it's a big improvement over vanilla.
-----
Where Expert AI improves on vanilla AI:
1. Much better at the factory-building game. You can expect AI opponents to have significantly higher numbers of military factories, without sacrificing civilian factories.
2. Much larger numbers of fighter planes by a factor of five or six. This is where a lot of the extra factories go.
3. Some improvement when it comes to research - no weird fixation on armoured cars, more fixation on rubber refining for Germany.
4. Some improvement in production - I'd say Expert AI has an edge over vanilla when it comes to avoiding equipment surpluses and deficits. It's not immune to deficits (see Soviet heavy tank production where they had a deficit that would take 250 days to resolve at the outbreak of Barbarossa) but you see fewer instances of a giant overstock of one thing while there's a giant shortage of another.
What Expert AI doesn't (can't?) really improve:
1. Naval production. There's still weirdness where the Allied AI doesn't use all its dockyards, and everyone still builds ships of obsolete designs, even if they've specifically spent research and naval XP to get better ones. Expert AI does get points for having everyone build fewer dockyards, thus lessening the problem a bit depending on which faction you're looking at.
2. Division positioning. Both versions of the AI love to keep around old trash divisions, and these find their way into high-priority fronts. Meanwhile expensive tank divisions are put on busywork, like guarding peaceful fronts. This can be exacerbated by some Expert AI settings,
3. Going to sea. The biggest offender here is Germany, but it applies to entire Axis - it'd probably also apply to the Comintern and Allies, but they have fewer overseas commitments and giant navies to keep their divisions safe-ish, respectively. Both versions of the AI love to send Axis divisions to Italian East Africa, sailing the whole way around Africa to do so. One of the biggest favours the UK can do the Axis is conquering Italian East Africa, and one of the biggest injuries the UK can inflict on the Axis is to put submarines in Cape Verde and the Gulf of Guinea.
4. Failing at the trade game. The vanilla AI had the USA build a ton of dockyards, run itself into a huge steel deficit, and then not buy more. Expert AI had the USSR build a ton of fighters, run itself into a large aluminium deficit, and then not buy more. I'd say the Expert AI version of this is better - running out of aluminium is better than running out of steel since you don't need aluminium to build basic things like infantry gear, but neither situation is great. There's less merit in the USSR building lots of extra factories if a lot of them are wasted due to lack of resources.
-----
Final Thoughts
I've attached the savegame, and the Expert AI mod can be found here. This isn't intended to be a hit-piece against the mod, merely an examination of what it does and how it compares to vanilla, keeping in mind that modders only have limited access to the game's code in order to make changes. It also isn't intended to be a hit-piece regarding the vanilla AI - Expert AI is trying to do the best job it can in a historical game, while the vanilla AI has to handle ahistoric games, total conversion mods and all sorts of player craziness.
I think if I had to set a priority for Paradox's AI coders, it'd be the AI's attitude to sending divisions by sea. At present it's far too willing to send divisions on enormous journeys, unescorted, across hostile seas, to unimportant destinations. At best it means that a lot of divisions are tied up at sea, and at worst it means a lot of divisions are sunk for no good reason. Ideally the AI would judge its level of sea control and have that be checked every time it considers sending a division to sea, meaning that in a historic game the Axis would fight the war in Africa mainly with the divisions it sent there pre-war.
Not having seen the code, it feels like the easiest thing to fix is the trade game, where the AI runs enormous deficits. Obviously it's not going to be as easy as "IF DEFICIT THEN BUY STUFF" but it's got to be easier than fixing the entire division positioning system, right?
Now, before I get into the specifics, some caveats. This was only a single game played, and it was on the latest version of the game which Expert AI has not yet been updated to support. Hopefully people find the information useful all the same.
Settings and DLCs:
Expert AI has a ton of settings - do you want the AI to play optimally, or follow historical templates? Do you want Japan to win the Sino-Japanese war, or not? Do you want the Axis to invade Norway? Etc etc etc. I left it on the default "challenging" settings, except that I changed "Sino-Japanese War: Favour Japan" to "Sino-Japanese War: Favour China", since China did win that war and I want a historical feel. It's not particularly important to Barbarossa though.
I have most HoI4 DLCs aside from cosmetic ones and Battle For The Bosporus. Most applicably, I have No Step Back.
Timeline:
The game progressed mostly historically, with the Spanish Civil War ending a few months earlier than reality, much better than the year-or-so early vanilla had.
I did notice some weirdness once WW2 started, with a French fast division barrelling into South Germany unsupported, making it all the way to Regensburg before being surrounded and destroyed. Germany then went straight through the Maginot line and Italy joined the war before even Poland fell. As a result, France fell before Germany even went after Belgium and the Netherlands.
I also saw the UK declare war on Iraq in July 1941. I wonder how much of this can be explained by the mod being set to "challenging" instead of "historical".
Now let's look at the USSR and Germany's situation on the day of Barbarossa in detail:
-----
Soviet Army:
254 divisions total, comprising 2.8 million manpower, 5580 AA guns, 4450 AT guns, 2410 artillery pieces, 240000 infantry gear, 4010 trucks, 14600 support gear, 1530 light tanks, and 1040 heavy tanks. The most common division type is the 186 infantry divisions (10 infantry battalions, one line AA battalion, support artillery, engineers, AT, logistics and maintenance), with four heavy tank divisions (14 heavy tank battalions, 7 motorised, with support engineers), and a lot of trash divisions (22 divisions of 4 cavalry battalions, 18 divisions of 6 infantry battalions with military police) that they started with.
This is a larger army than the vanilla AI built, and also a lot more homogenous, with the vast majority being of one template where the vanilla AI is a bit all over the place. The vanilla AI leans heavily on line artillery and light tanks, while the Expert AI goes heavily into support companies and a few very large heavy tank divisions.
98 of the Soviet divisions are on the German border, 92 of them being infantry, 4 mountaineers, and 2 cavalry. Notably there are no tanks on the German border. This is kind of funny given that the German AI has gone to the trouble not only to put AT guns in all its divisions, but also to research AT gun tech ahead of time. Manpower-wise, the Expert AI has very slightly more manpower on the front with Germany, but probably somewhat less power due to having much fewer artillery and tanks.
So where are the enormous, expensive Soviet tank divisions? They're all on the border with Romania. Given that Romania will join the war soon, that's not a disaster. I'd have put them on the border with Germany, though. The Romanian border is well-guarded, with 38 infantry divisions, the entire heavy tank strength of the USSR, and a half dozen trash cavalry and light tank divisions.
The Hungarian border has 15 infantry divisions, and some trash NKVD and light tank divisions.
15 divisions, mostly trash, are on the Japan front. Not as bad as the vanilla AI, which had 29. What is as bad as the vanilla AI is the guards for the interior of the USSR, with over 50 divisions guarding various unimportant points, including the traditional 3 divisions in Dudinka and garrisons for islands between the US and USSR.
I'm not sure what control mods can have over how the AI distributes its divisions, this looks pretty similar to how the vanilla AI did things.
Soviet Stockpiles:
3.44 million manpower
964 AA
-745 AT
480 art
9000 infantry gear
-313 truck
-487 support gear
-563 light tanks
-1100 heavy tanks
128 train
-36 strat
80 transport planes
121 fighters
90 nav
-73 tac
423 convoy
Notable here is that Expert AI has solved the Soviet manpower crisis - in vanilla they only had 200,000 manpower left. There's also not the huge stockpile of infantry gear vanilla AI had, probably because they're training another 60 infantry divisions. They are significantly undersupplied in the heavy tank department - their divisions are at about half strength there.
Soviet Air Forces:
These are generally much larger than in vanilla, with 6000 fighters to vanilla's 1000, but no CAS where vanilla had a couple of thousand.
This is a big improvement over vanilla - there's no point having CAS without enough fighters to defend them, while fighters will do just fine without CAS.
Miscellaneous Thoughts:
Severe heavy tank shortage - basically four divisions are deployed when there are only enough tanks for two. All of those divisions are on the Romanian border - not great, not terrible.
The heavy tank division probably doesn't need to be accompanied with motorised infantry - the tanks only go 4.7 kph. Maybe replace the motorised with leg infantry and give the tanks worse engines if they're going to be this slow?
Naval production's a bit crap - three lines of early destroyers when 1936 destroyers are available.
-84 aluminium shortage! They are importing from Switzerland, Manchukuo, Sinkiang, Malaya and Sweden, but the US, UK, and even Vichy France are available and not being used.
-----
German Army:
147 divisions total, comprising 2.5 million manpower, 7190 AA guns, 3020 AT guns, 17400 artillery pieces, 185000 infantry gear, 5250 trucks, 13600 support gear, 2700 medium tanks, 432 medium self-propelled AA guns, 532 medium self-propelled artillery, and 243 medium tank destroyers. The army is pretty homogenous, with 120 divisions being 14 infantry battalions, 4 artillery battalions, 2 AA gun battalions, with support engineers, AT, logistics, hospitals and maintenance. The six tank divisions have 9 medium tank battalions, 2 medium self-propelled artillery battalions, 2 medium self-propelled AA gun battalions, 1 medium tank destroyer, and 6 motorised battalions, with support engineers, AT, logistics and maintenance battalions.
This is a similarly-sized army to what the vanilla AI built, but concentrated into far fewer divisions. The focus on medium tanks and line artillery is still in place.
The Expert AI has done a fair bit better than the vanilla AI when it comes to positioning its divisions. They've managed to get 86 of their divisions onto the Soviet border, 58% of the army, compared to vanilla's 29%.
Where the Expert AI has not improved on vanilla is its fixation with Italian East Africa - 23 divisions are sailing between Europe and Italian East Africa, including two of the six tank divisions.
Positioning of tank divisions is better than vanilla, but whether this is just luck, I'm not sure. Three out of six tank divisions are on the Soviet border, with two at sea off Africa, and one guarding the Norwegian coast.
German Stockpiles:
500000 manpower
1400 AA
-42 AT
-106 art
35000 infantry gear
1700 truck
341 support gear
1100 light tank
-4 medium tank
734 train
714 medium SPAA
-144 medium SPART
-79 marm
55 transport planes
169 fighters
13 CAS
100 Naval Bombers
-76 TAC
824 convoy
These are better than vanilla, which had a ton of surplus infantry gear and artillery, with big truck and tank deficits.
German Air Forces:
Again, far more fighters than vanilla - 5000 vs 1000. There's also a bigger focus on naval bombers, with 400 versus the 100 of vanilla. CAS numbers are similar, with 1000 on both AI versions, and vanilla has 700 tactical and 200 strategic bombers that Expert AI does not.
I'd definitely take the Expert AI version of this over the vanilla AI one - fighters are king.
Miscellaneous Thoughts:
Logistics are pretty good - there are a thousand or so light tanks doing nothing in the stockpile, could be worth using those until they fall apart.
Research is about right. Rubber refining has been researched which is allowing a ton of plane production - this is a big improvement over vanilla. The crazy focus on armoured car research is gone. AT guns have been researched ahead of time, which is kind of funny given that the Soviet AI hasn't managed to bring a tank to the German border.
Tanks aren't as slow as the Soviet ones which are barely faster than walking, but they're only doing 6.7 kph.
-----
Factory counts, (compared to vanilla):
| Factory Type | Axis plus Prosperity Sphere | Comintern | Allies |
| Military | 409 (+93 vs vanilla) | 206 (+89 vs vanilla) | 385 (+103 vs vanilla) |
| Dockyard | 102 (-1 vs vanilla) | 9 (-12 vs vanilla) | 121 (30 not in use!) (-64 vs vanilla) |
| Civilian | 336 (+60 vs vanilla) | 144 (+18 vs vanilla) | 379 (+3 vs vanilla) |
This is a significant improvement over the vanilla AI - it's generally accepted that military factories are king, especially when it comes to Barbarossa, and all three factions have many more military factories as well as more civilian factories to boot.
The Allies have considerably fewer dockyards in Expert AI, but given that they're still comfortably ahead at sea, they're not even using all the dockyards they have, and the ones they are using are building bad ships (early destroyers when they have 1936 designs, 1936 cruisers when they have 1940 designs), I think this is a good sacrifice for them to make.
A lot of these extra military factories are going into fighter production - this is generally a good thing and will make the AI much more threatening and harder to dominate with air power. There is an issue where the USSR has far too little aluminium and isn't trading for enough, but on the whole it's a big improvement over vanilla.
-----
Where Expert AI improves on vanilla AI:
1. Much better at the factory-building game. You can expect AI opponents to have significantly higher numbers of military factories, without sacrificing civilian factories.
2. Much larger numbers of fighter planes by a factor of five or six. This is where a lot of the extra factories go.
3. Some improvement when it comes to research - no weird fixation on armoured cars, more fixation on rubber refining for Germany.
4. Some improvement in production - I'd say Expert AI has an edge over vanilla when it comes to avoiding equipment surpluses and deficits. It's not immune to deficits (see Soviet heavy tank production where they had a deficit that would take 250 days to resolve at the outbreak of Barbarossa) but you see fewer instances of a giant overstock of one thing while there's a giant shortage of another.
What Expert AI doesn't (can't?) really improve:
1. Naval production. There's still weirdness where the Allied AI doesn't use all its dockyards, and everyone still builds ships of obsolete designs, even if they've specifically spent research and naval XP to get better ones. Expert AI does get points for having everyone build fewer dockyards, thus lessening the problem a bit depending on which faction you're looking at.
2. Division positioning. Both versions of the AI love to keep around old trash divisions, and these find their way into high-priority fronts. Meanwhile expensive tank divisions are put on busywork, like guarding peaceful fronts. This can be exacerbated by some Expert AI settings,
3. Going to sea. The biggest offender here is Germany, but it applies to entire Axis - it'd probably also apply to the Comintern and Allies, but they have fewer overseas commitments and giant navies to keep their divisions safe-ish, respectively. Both versions of the AI love to send Axis divisions to Italian East Africa, sailing the whole way around Africa to do so. One of the biggest favours the UK can do the Axis is conquering Italian East Africa, and one of the biggest injuries the UK can inflict on the Axis is to put submarines in Cape Verde and the Gulf of Guinea.
4. Failing at the trade game. The vanilla AI had the USA build a ton of dockyards, run itself into a huge steel deficit, and then not buy more. Expert AI had the USSR build a ton of fighters, run itself into a large aluminium deficit, and then not buy more. I'd say the Expert AI version of this is better - running out of aluminium is better than running out of steel since you don't need aluminium to build basic things like infantry gear, but neither situation is great. There's less merit in the USSR building lots of extra factories if a lot of them are wasted due to lack of resources.
-----
Final Thoughts
I've attached the savegame, and the Expert AI mod can be found here. This isn't intended to be a hit-piece against the mod, merely an examination of what it does and how it compares to vanilla, keeping in mind that modders only have limited access to the game's code in order to make changes. It also isn't intended to be a hit-piece regarding the vanilla AI - Expert AI is trying to do the best job it can in a historical game, while the vanilla AI has to handle ahistoric games, total conversion mods and all sorts of player craziness.
I think if I had to set a priority for Paradox's AI coders, it'd be the AI's attitude to sending divisions by sea. At present it's far too willing to send divisions on enormous journeys, unescorted, across hostile seas, to unimportant destinations. At best it means that a lot of divisions are tied up at sea, and at worst it means a lot of divisions are sunk for no good reason. Ideally the AI would judge its level of sea control and have that be checked every time it considers sending a division to sea, meaning that in a historic game the Axis would fight the war in Africa mainly with the divisions it sent there pre-war.
Not having seen the code, it feels like the easiest thing to fix is the trade game, where the AI runs enormous deficits. Obviously it's not going to be as easy as "IF DEFICIT THEN BUY STUFF" but it's got to be easier than fixing the entire division positioning system, right?
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