History Videogame / HeartsOfIron

** [=DLCs=] for ''IV'' introduced designers for ships, tanks and planes, allowing them to tailor them either for specific tasks, or, much more often, exploit various loopholes in gameplay mechanics and meta. Even without [=DLCs=], experience can be used to alter hardware, providing variants with slightly different stats. The AI is notoriously incapable of using ''either'' of those systems, completely messing up DLC-backed designs (since there are no "default" models) and treating regular variants as endless experience sinks for no real benefits.

** [=DLCs=] for ''IV'' introduced designers for ships, tanks and planes, allowing them to tailor them either for specific tasks, or, much more often, exploit various loopholes in gameplay mechanics and meta. AI is notoriously incapable of using those hardware designers.

* [=DLCs=] from ''IV'' are quite infamous due to their inherit PowerCreep, but two countries with DLC-granted focus trees stand out the most when it comes to Magikarp status. AI is scripted to ''not'' do them, and they seem like a ViolationOfCommonSense for human player, but still:
** Normally, Yugoslavia is your average minor with some extra aluminium that can think about becoming a regional power. With ''Death or Dishonor'', Yugoslavia can [[BalkanizeMe self-balkanize]], which, contrary to what it looks like, makes it way, way stronger than a unified state. Each of the split-off countries remains the puppet of the central, while having access to the generic focus tree, each roughly corresponding to a single state. That in turn means each of those states gets full benefit from the economic part of the focus tree (maxed out infrastructure, 4 civilian and 3 military factories - with free slots for those - and maybe also level 2 airport). Normally that's barely noticeable... but Yugoslavia can release staggering ''nine'' puppets that can be then simply integrated back. That's potential for up to 36 civilian and 27 military factories in max infrastructure states. For some perspective - that's more than the starting industry of Germany. And both Yugoslavia and its puppets can obviously expand in the meantime. Most importanty, however, Yugoslavia can achieve all of this by late 1938, maybe early 1939 if the AI picks the "wrong" focuses for puppets.
** Ethiopia under ''By Blood Alone'' can go through a near identical situation, except it ''also'' gains free resources and ''only'' when going for the BalkanizeMe focuses. The resulting country is insanely powerful due to the size of its industrial base and doesn't need to trade for resources with the outside world, having ''zero'' problems with world conquest or fulfilling its seemingly tough achievements (conquering Egypt, Palestine and large sections of East Africa). At the game's start, Ethiopia is semi-tribal country with barely any industry or technology and is already fighting a war against Italy, being overrun under AI control in less than 2 months.

* AlternateHistoryWank: Any good player will cause this in the nation they play as: [[CrapsackWorld Germany conquering the Soviet Union and the world,]] [[UsefulNotes/SecondSinoJapaneseWar Japan conquering China,]] [[HoldTheLine France or even Poland holding off the Nazi tide,]] [[RedScare the red flag flying over all of Europe]], [[AmericaTakesOverTheWorld the United States conquering the Soviet Union and Germany]], a boatload of historically neutral nations (Argentina, Sweden, Turkey, Afghanistan, Saudi Arabia, Iran, Spain, and so on) joining either side, the Republicans winning the UsefulNotes/SpanishCivilWar (either the main faction, or after a takeover by the anarchists), [[{{ForeverWar}} WWII lasting beyond 1945]], the Nationalists winning the Chinese civil war, etc. Anything is possible. Hearts of Iron 4 provides even wilder scenarios and plotlines in shape of focus trees, such as Turkey coring ''Finland'' because their lineage can be traced back to Ural-Altay tribes.

** While their sprites are shown using bolt-actions, the Polish forces are issued the Kbsp wz.1938M semiautomatic rifle. This is particularly egregious as only 150 were built, and practically all Polish soldiers used the bolt-action Kbk wz.29 instead.

* PowerupLetdown: Intelligence agencies in general, and tech-stealing in particular from ''IV''. For the time and factories invested in it, the results are just insulting. There are at least 3 different mods that simply slash the time needed for espionage missions to make them even remotely worthwhile.

** ''Waking the Tiger'' (8 March 2018), the ''Cornflakes'' update, which adds/revises focuses trees for Germany, [[UsefulNotes/SecondSinoJapaneseWar China, and Japan]], including the various Chinese warlords and Manchukuo. Also adds new General abilities to add more flexibility to combat.

** ''LaResistance'' (25 February 2020), the ''Husky'' update, which adds/revises focuses trees for Spain (including every faction in the [[UsefulNotes/SpanishCivilWar Spanish Civil War]]), France (including Free France and Vichy France), and Portugal. Also adds a brand new system of espionage to uncover enemy intel.

** ''By Blood Alone'' (27 September 2022), the ''Avalanche'' update, which adds/revises focus trees for Italy, Ethiopia, and Switzerland. Also overhauls the peace deal system and revises the Ship Designer (again), while adding a new Plane Designer. With this update, every nation with a focus tree at launch will have gained reworked content.
** ''Arms Against Tyranny'' (Autumn 2023), which adds new focus trees for the Nordic countries (Finland, Sweden, Norway, and Denmark), as well as adding a new industry designer and an international arms market mechanic.

* ForegoneConclusion: Various historical events, along with [=WW2=] itself, will happen each and every time, across all the games in the series. In case of ''II'' and especially in ''Darkest Hour'' it also means certain events will play out ''despite'' player intervention: Spanish Civil War will still happen (despite having three extra years of preparation and in theory ability to act against future Nationalist's commanders), 4th encirclement of the Jiangxi Soviet will fail (even if you micromanage it enough to completely over-run them and wipe out all troops), Tianjin Garrison can't be disbanded (and so it will get Japan into 2nd Sino-Japanese War) etc. ''II'' most infamously had a hard-coded event for admiral Isoroku Yamamoto to be shot down with his plane on April 18, 1943, with absolutely nothing to prevent that - and even without the event itself, tech-team representing him was expiring on that date.

** Most often seen when importing in a scenario from ''VideoGame/VictoriaAnEmpireUnderTheSun''. Whilst the borders and existing countries will change, the leaders most often won't. Meaning that you can have UsefulNotes/AdolfHitler in charge of a democratic Germany, with or without the UsefulNotes/WorldWarI scenario having happened.
** Tech teams in II are hard-coded. This means two things: you are stuck with whatever is pre-defined for your country without any ability to upgrade or switch[[note]]Eventually, an option to capture tech teams of conquered nations was added to alleviate this[[/note]] and, much worse, they came with a historical expiration date. This is probably most prominent with Japan, which might [[JapanTakesOverTheWorld take over the world]], but come September '45, it will get completely defanged with its military tech-teams, as by the game logic, Japan should surrender by then.
** Great Britain is hardcoded to always declare war to Germany in the Forties, no matter what is the geopolitical situation. Even if you managed to play Germany as a democratic state with peaceful relations with Poland and the Western Europe.
** In IV, there's a chance that someone will spot the problem that would have caused the Hindenburg disaster, resulting in it safely reaching the its destination. However, it's stated that the public's trust in airship travel is still shattered due to how close it came to disaster, since the problem[[note]]It should be noted that, while the game does outright say what caused the disaster, in real life the cause is unknown to this very day, with several different theories floating around[[/note]] was only discovered by a stroke of luck.

** Military police companies in ''IV'' - they're not flashy and don't have any particularly neat effects for combat divisions like engineers or recon and don't have the raw stats of support artillery, but especially with the integrated support branch of the superior firepower doctrine, they are the absolute most IC-efficient source of soft attack in the game, and do so at no combat width cost, and have manpower efficiency only surpassed by artillery. With the integrated support bonuses, they're essentially an entire additional infantry battalion that takes no frontage and only uses half as many rifles and half as much manpower.

* TakeOverTheWorld: It is indeed possible ([[DifficultButAwesome but difficult]]) to do this. Even as [[JokeCharacter Luxembourg]], as demonstrated [[https://youtu.be/-8kMkNMCNrg here.]]

** Also in ''IV'', any minor country that got its own national focus tree thanks to a DLC usually suffers from a significant nerf. The generic focus tree is nothing fancy, but it offers very upfront and easy to get benefits, significantly bolstering your starting position. Country-specific focus trees, meanwhile, tend to introduce a whole host of esoteric mini-games and usually provide less factories, less research bonuses and far less options to switch your government, spread over few times larger tree. Most prominent examples are the Chinese warlords[[note]]Especially when compared with a Japanese puppet state of Mengkukuo, which gets ''thrice'' as many factories, massive infrastructure improvements and potential for enormous recruitment bonus before the Second Sino-Japanese War starts, while warlords will be given almost nothing from their focus trees[[note]]), Baltic countries and Ethiopia, who all went from "drab, but decent" to "elaborate, but mostly useless".

* BlatantLies: In ''IV'', the [[UsefulNotes/TheBritishRaj British Raj]]/[[UsefulNotes/{{India}} India]] has the "Agrarian Society" national spirit, which reduces the recruitable population by 69% due to local traditions that make the drafting of farmers unacceptable. While the game describes it as "''This belief is so wide-spread and well-entreched that it will require at least a generation to overcome''", it is actually impossible to remove this from India. Change of ideology or winning independence doesn't remove this national spirit. Even if India were to have a civil war, both sides will still retain this national spirit. This was rectified after updates that came around the time of ''By Blood Alone'', which did allow a player-controlled Raj to remove the spirit completely.
** However, there is a way to get rid of this spirit if you aren't playing as the Raj: Pakistan, Burma, and Bangladesh will not have this spirit if you satellite them as puppets, and if you form a collaboration government from the British Raj, said collaboration government won't have the spirit.

* EternalEquinox: Day and night do vary with latitude, so days are shorter in the Northern Hemisphere. But they're always shorter in the North -- apparently, it's always winter there.

* BlatantLies: In ''IV'', the [[UsefulNotes/TheBritishRaj British Raj]]/[[UsefulNotes/{{India}} India]] has the "Agrarian Society" national spirit, which reduces the recruitable population by 69% due to local traditions that make the drafting of farmers unacceptable. While the game describes it as "''This belief is so wide-spread and well-entreched that it will require at least a generation to overcome''", it is actually impossible to remove this from India. Change of ideology or winning independence doesn't remove this national spirit. Even if India were to have a civil war, both sides will still retain this national spirit.