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Hearts of Iron IV
Hearts of Iron IV, also commonly known as HOI4, is a 2016 grand strategy video game developed by Paradox Development Studio and published by Paradox Interactive. It is the sequel to 2009's Hearts of Iron III and the fourth main installment in the Hearts of Iron series. Like previous games in the series, Hearts of Iron IV is a grand strategy wargame that focuses on World War II. The Player can play as any Nation on the map, starting either in 1936 or 1939. Players have the option of following a nation's historical path, or leading various non-historical paths.
By May 2018, the game had sold a total of one and a half million copies worldwide. As of November 2025, the game has sold over seven million copies on Steam alone.[not verified in body] Since its release, Paradox has released large amounts of downloadable content for Hearts of Iron IV.
Hearts of Iron IV is a grand strategy wargame that revolves around World War II. The player may play as any nation in the world in the 1936 or 1939 start dates in single-player or multiplayer. A nation's military is divided between ground forces, naval forces, and aerial forces. For the ground forces, the player may train, customize, and command divisions consisting of various types of infantry, tanks, and other units. These divisions require equipment and manpower to fight properly. The navy and air force also require men and equipment, including the actual warships and warplanes that are used in combat. The tanks, airplanes, and boats could also be manually customized by the player. Equipment is produced by military factories, while ships are built by dockyards. These military factories and dockyards are, in turn, constructed using civilian factories, which also construct a variety of other buildings, produce consumer goods for the civilian population, and oversee commerce with other nations. Most nations are initially forced to devote a significant number of their civilian factories to producing consumer goods, but as the nation becomes increasingly mobilized, more factories will be freed up for other purposes. Mobilization is represented as a "policy" that the player may adjust with the proper amount of political power, an abstract "resource" that is also used to appoint new ministers and change other facets of the nation's government. In addition to mobilization, there are other policies, including the nation's stance on conscription and commerce.
Land in Hearts of Iron IV is divided into tiny regions known as provinces (also called tiles), which are grouped to form states. Each state has a certain amount of shared and state building slots, both of which affect the whole state, while provinces have province building slots that only impact the individual province. Similarly, major seas and oceans (for warships) and the sky (for warplanes) are divided into different zones known as strategic regions. Sea regions and provinces each have a type of terrain and weather assigned to them that determines how well different types of units will perform in combat there. Air regions do not have terrain types but still have weather. Divisions are deployed in provinces and can capture enemy provinces and engage in combat. How well divisions perform in combat depends on various factors, such as the quality of their equipment, the weather, the type of terrain, the skill and traits of the general commanding the divisions, aerial combat in the region, supply lines, their organisation, how high their defense or attack - 'soft' or 'hard' - is, and supporting units. Technologies can be researched to improve equipment. Military doctrines can be upgraded by using army XP, among other things, which often means that a more technologically advanced nation will have an edge in combat. If a division (or a group of divisions) successfully overwhelms an enemy province, they may occupy it. Some provinces may have victory points, which can push a nation closer towards capitulation if occupied. Occupying key provinces within a state allows the occupying power to access the enemy's factories and natural resources in that state. Resistance to occupation within a state, which occurs when a nation does not have a 'core' on a controlled territory, can hamper the occupying power's control over it. Nations can develop nuclear bombs if they have the proper technology, which can be used to devastate enemy provinces and states. Since the release of the update coinciding with Götterdämmerung, special projects have been added which require facilities to be constructed to allow for the pursuit of nuclear energy, as well as other technologies such as super heavy tanks, intercontinental bombers, or rockets.
Hearts of Iron IV also attempts to recreate the complex diplomatic relationships of the day. Nations may undertake a variety of diplomatic actions; they may sign non-aggression pacts, guarantee the independence of other nations, and offer or request military access, amongst other things. Another key feature of diplomacy is the ability to create a faction or invite other nations to an existing one. Factions represent the main alliances of the era, like the Axis and Allies (for gameplay purposes, real-world factions like the Axis and Allies are split into numerous smaller factions, like the Comintern, the Chinese United Front, and the Greater East Asian Co-Prosperity Sphere). Faction members may assist each other in wars, making faction members precious assets. Some more clandestine diplomatic actions are also available. For example, the player may justify war against other nations, spread their ideology abroad, or stage a coup. Countries in the game may be democratic, communist, fascist, or non-aligned. Each of the four ideologies has advantages and disadvantages; for example, fascist nations can go to war with other countries easily, but other nations are not as willing to trade with them as they are with democratic countries. If a nation's ideology is non-aligned, then it can be several things. For an example, if the German Reich loses a civil war, a monarchist party is created, which is non-aligned. If a different ideology becomes too popular in a country, a referendum may be held that will peacefully convert the nation to the most popular ideology. Otherwise, ideologies may come to power violently through coups, civil wars, or forced subjugation by a foreign power.
This diplomacy is further expanded through the addition of espionage in the expansion La Résistance, which extends gameplay in the management of occupied territories which is done differently according to player choices and ideology. Furthermore, the operation of spy networks allows nations to steal technology, gather information on an opponent's military, and engage in other espionage efforts.
While Hearts of Iron IV does feature some scripted events, the game features a "national focus" system that makes fixed events less necessary than in previous installments in the series. Each country in the game has a "focus tree" with various "national focuses" that grant certain effects or trigger events. For example, for the Anschluss to occur, Germany must first complete the focus that is related to it. Other focuses can grant special bonuses, like faster research times for certain technologies or extra factories. While some bonuses (like extra factories) are very tangible, others (like improvements to morale) are more abstract. These abstract bonuses are represented by "national spirits" that can be temporary or permanent. Not all national spirits are granted by focuses, and not all spirits are entirely beneficial. Focuses are completed over time; only one focus may be worked on at once, and working on one consumes some political power. Initially, only a handful of key nations, like Nazi Germany, the United Kingdom, the Soviet Union, and the United States, had unique focus trees; all other nations shared a generic one. Subsequent updates and DLCs have added focus trees to other nations as well.
Hearts of Iron IV also introduces the concept of "world tension", an abstract representation of how close the world is to global war, on a scale from 0 to 100. Aggressive actions by any nation can increase world tension, while peaceful actions can decrease it. Depending on the circumstances of a nation, like their ideology, a certain level of world tension may be necessary to perform certain actions, like justifying war against another country.
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Hearts of Iron IV
Hearts of Iron IV, also commonly known as HOI4, is a 2016 grand strategy video game developed by Paradox Development Studio and published by Paradox Interactive. It is the sequel to 2009's Hearts of Iron III and the fourth main installment in the Hearts of Iron series. Like previous games in the series, Hearts of Iron IV is a grand strategy wargame that focuses on World War II. The Player can play as any Nation on the map, starting either in 1936 or 1939. Players have the option of following a nation's historical path, or leading various non-historical paths.
By May 2018, the game had sold a total of one and a half million copies worldwide. As of November 2025, the game has sold over seven million copies on Steam alone.[not verified in body] Since its release, Paradox has released large amounts of downloadable content for Hearts of Iron IV.
Hearts of Iron IV is a grand strategy wargame that revolves around World War II. The player may play as any nation in the world in the 1936 or 1939 start dates in single-player or multiplayer. A nation's military is divided between ground forces, naval forces, and aerial forces. For the ground forces, the player may train, customize, and command divisions consisting of various types of infantry, tanks, and other units. These divisions require equipment and manpower to fight properly. The navy and air force also require men and equipment, including the actual warships and warplanes that are used in combat. The tanks, airplanes, and boats could also be manually customized by the player. Equipment is produced by military factories, while ships are built by dockyards. These military factories and dockyards are, in turn, constructed using civilian factories, which also construct a variety of other buildings, produce consumer goods for the civilian population, and oversee commerce with other nations. Most nations are initially forced to devote a significant number of their civilian factories to producing consumer goods, but as the nation becomes increasingly mobilized, more factories will be freed up for other purposes. Mobilization is represented as a "policy" that the player may adjust with the proper amount of political power, an abstract "resource" that is also used to appoint new ministers and change other facets of the nation's government. In addition to mobilization, there are other policies, including the nation's stance on conscription and commerce.
Land in Hearts of Iron IV is divided into tiny regions known as provinces (also called tiles), which are grouped to form states. Each state has a certain amount of shared and state building slots, both of which affect the whole state, while provinces have province building slots that only impact the individual province. Similarly, major seas and oceans (for warships) and the sky (for warplanes) are divided into different zones known as strategic regions. Sea regions and provinces each have a type of terrain and weather assigned to them that determines how well different types of units will perform in combat there. Air regions do not have terrain types but still have weather. Divisions are deployed in provinces and can capture enemy provinces and engage in combat. How well divisions perform in combat depends on various factors, such as the quality of their equipment, the weather, the type of terrain, the skill and traits of the general commanding the divisions, aerial combat in the region, supply lines, their organisation, how high their defense or attack - 'soft' or 'hard' - is, and supporting units. Technologies can be researched to improve equipment. Military doctrines can be upgraded by using army XP, among other things, which often means that a more technologically advanced nation will have an edge in combat. If a division (or a group of divisions) successfully overwhelms an enemy province, they may occupy it. Some provinces may have victory points, which can push a nation closer towards capitulation if occupied. Occupying key provinces within a state allows the occupying power to access the enemy's factories and natural resources in that state. Resistance to occupation within a state, which occurs when a nation does not have a 'core' on a controlled territory, can hamper the occupying power's control over it. Nations can develop nuclear bombs if they have the proper technology, which can be used to devastate enemy provinces and states. Since the release of the update coinciding with Götterdämmerung, special projects have been added which require facilities to be constructed to allow for the pursuit of nuclear energy, as well as other technologies such as super heavy tanks, intercontinental bombers, or rockets.
Hearts of Iron IV also attempts to recreate the complex diplomatic relationships of the day. Nations may undertake a variety of diplomatic actions; they may sign non-aggression pacts, guarantee the independence of other nations, and offer or request military access, amongst other things. Another key feature of diplomacy is the ability to create a faction or invite other nations to an existing one. Factions represent the main alliances of the era, like the Axis and Allies (for gameplay purposes, real-world factions like the Axis and Allies are split into numerous smaller factions, like the Comintern, the Chinese United Front, and the Greater East Asian Co-Prosperity Sphere). Faction members may assist each other in wars, making faction members precious assets. Some more clandestine diplomatic actions are also available. For example, the player may justify war against other nations, spread their ideology abroad, or stage a coup. Countries in the game may be democratic, communist, fascist, or non-aligned. Each of the four ideologies has advantages and disadvantages; for example, fascist nations can go to war with other countries easily, but other nations are not as willing to trade with them as they are with democratic countries. If a nation's ideology is non-aligned, then it can be several things. For an example, if the German Reich loses a civil war, a monarchist party is created, which is non-aligned. If a different ideology becomes too popular in a country, a referendum may be held that will peacefully convert the nation to the most popular ideology. Otherwise, ideologies may come to power violently through coups, civil wars, or forced subjugation by a foreign power.
This diplomacy is further expanded through the addition of espionage in the expansion La Résistance, which extends gameplay in the management of occupied territories which is done differently according to player choices and ideology. Furthermore, the operation of spy networks allows nations to steal technology, gather information on an opponent's military, and engage in other espionage efforts.
While Hearts of Iron IV does feature some scripted events, the game features a "national focus" system that makes fixed events less necessary than in previous installments in the series. Each country in the game has a "focus tree" with various "national focuses" that grant certain effects or trigger events. For example, for the Anschluss to occur, Germany must first complete the focus that is related to it. Other focuses can grant special bonuses, like faster research times for certain technologies or extra factories. While some bonuses (like extra factories) are very tangible, others (like improvements to morale) are more abstract. These abstract bonuses are represented by "national spirits" that can be temporary or permanent. Not all national spirits are granted by focuses, and not all spirits are entirely beneficial. Focuses are completed over time; only one focus may be worked on at once, and working on one consumes some political power. Initially, only a handful of key nations, like Nazi Germany, the United Kingdom, the Soviet Union, and the United States, had unique focus trees; all other nations shared a generic one. Subsequent updates and DLCs have added focus trees to other nations as well.
Hearts of Iron IV also introduces the concept of "world tension", an abstract representation of how close the world is to global war, on a scale from 0 to 100. Aggressive actions by any nation can increase world tension, while peaceful actions can decrease it. Depending on the circumstances of a nation, like their ideology, a certain level of world tension may be necessary to perform certain actions, like justifying war against another country.