* BrokenBase:
** The announcement that IV would only have about three political parties angered most of the community as it was seen as a major step backwards from the 10 parties you had in HOI3, though some Paradox fans are fine with it.
** The exclusion of Manchukuo from Hearts of Iron IV has divided many fans. One side claims that the Japanese in previous Hearts of Iron games have poorer chance against China, thus eliminating Manchukuo would be the best step in giving the Japanese more edge. The other side are either fans of playing the puppet state in the previous games or want to preserve as much as historical accuracy as possible.
* GameBreaker:
** The United States is pretty much considered "easy mode", and for good reason, particularly in ''III''. They start off with the largest amount of IC in the game, the biggest knowledge pool, and a ''very'' powerful navy -- and it only gets bigger and meaner as the game progresses. The only weaknesses the US has is that, starting out, they have a weak army and air force and low technology, so using that knowledge pool is essential to catch up with the rest of the world. But by '45, the US will almost always be in a dominant position, as the only other economic powerhouse, the USSR, will have almost certainly spent a lot of resources and taken a lot of damage fighting Germany. All of this isn't just TruthInTelevision, it's actually ''toned down'' compared to how powerful the US economy was in UsefulNotes/WorldWarII, complete with the fact that, by the end, [[UsefulNotes/ColdWar the USSR was the only nation that could hope to compete with them]]. Later expansions make the US even more broken, with ''For The Motherland'' actually allowing the US to get a massive manpower boost once "The Day of Infamy" event triggers, which not only adds 400+ manpower instantly to their pool, but also revokes The New Deal (which imposed a manpower penalty on the USA) and gives a 25% bonus to manpower growth for a couple of years.
** In ''III'', using wars with minor countries to let you pass Total Economic Mobilization and Service By Requirement laws lets you swell your IC and manpower by a hilarious degree before World War II starts. Especially bad if you're a major power, and just ignore the "war" while you build up a huge number of divisions, planes, and ships. This got so bad that for the ''Their Finest Hour'' expansion, a special restriction was set where those laws could only be passed if the enemy you faced had a minimum of ''half'' your IC, otherwise you're stuck with just War Economy and Three-Year-Draft.
** Earlier editions of ''III'' turned your intelligence apparatus into one of these when used properly. The "Sabotage Production" mission, when coupled with "Counterintelligence" to eliminate enemy domestic spies, enabled allowed you to utterly cripple an enemy's industrial capacity, to the point that, for example, Germany would take months to conquer Poland and would get stonewalled in France, leaving them ripe for an American or Soviet attack. Later expansions removed the ability to sabotage production.
** With proper aiming and planning, paratroopers can shut down an entire offensive or defensive. Dropping them in the middle of enemy supply routes or on top of chokepoints can cut off supplies for weeks or months, and using them to hit "behind the lines" victory point provinces can trigger a total surrender with the right timing.
** Playing fascist is seen as this in Hearts of Iron 4. You can get yourself ready for war faster, can have a larger manpower pool, can invade other countries and puppet them easily, and can have numerous industry-boosting attributes. Democracies and Communism are seen as inferior, compared to it.
* GoodBadBugs: One patch for Darkest Hour had instances where after the Soviet Union lost a war against the axis and accepting the bitter peace event, [[UsefulNotes/VladimirLenin Lenin]] would take over as Head of State of the Soviet Union, cue jokes about Zombie Lenin coming back to {{Set right what once went wrong}}
* MagikarpPower: Nationalist China starts out with abysmal units and research teams and a non-existent navy, but has plenty of IC. If you play your cards right, you can turn it around and turn China into a formidable nation not to be messed with.
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