Hearts of Iron IV

• 1. Introduction

  ›

  Hearts of Iron IV is a World War II grand strategy game from Paradox Development Studio, and it lets a player take command of nearly any nation on the map. Fans commonly call it HOI4. Polygon found a striking example of its openness in a man named Eleazar López Contreras. The review described him as "a Venezuelan fascist with two army divisions and 12 fighter planes to his name." Choosing him means starting a world war with those modest forces and nothing more. How does one set of rules govern both a great power and a tiny government? Why did the game slip past its first release window? What have players built on top of it, and why did one country ban it?

  77386

• 2. Factories and Political Power

  ›

  On the 1st of January 1936 or the 14th of August 1939, depending on the chosen start date, every nation opens with the same puzzle about factories. Civilian factories are the foundation of the economy. They construct military factories, which produce equipment, and dockyards, which build ships. They also put up other buildings, make consumer goods for the civilian population, and oversee trade with other nations. Most countries must pour a large share of their civilian factories into consumer goods at first. Only as a nation mobilizes do more factories become free for other work.

  Political power, an abstract resource, works as a second currency. It pays for changes to mobilization, conscription and trade laws, which the game treats as policies. It also pays for appointing new ministers and for other changes to a government.

  Coal became a constraint with the update that came alongside the expansion No Compromise, No Surrender. Since then, all factories need to be powered by coal. Technologies, and buildings in states such as dams or nuclear power plants, can change how much power coal provides. The expansion Arms Against Tyranny added a global arms market and military industrial organizations that improve equipment over time. All of this production has one destination: divisions standing on a map cut into very small pieces.

  1343231086

• 3. Provinces and Divisions

  ›

  Provinces, also called tiles, are the smallest pieces of land in the game, and they are grouped together to form states. Each state has shared and state building slots that affect the whole state. A province has its own slots that affect only that province. Seas and oceans, where warships sail, and the sky, where warplanes fly, are divided into strategic regions. Sea regions and provinces each carry a terrain type and weather that decide how well different units perform there. Air regions have weather but no terrain.

  Ground forces are divisions that the player can train, customize and command. They are built from infantry, tanks, cavalry, motorized and mechanized battalions, and they need equipment and manpower to fight properly. The navy and air force need men and equipment too, including the warships and warplanes themselves. Players can also customize tanks, airplanes and boats by hand.

  A battle's outcome depends on equipment quality, weather, terrain, aerial combat in the region and supply lines. The skill and traits of the commanding general matter, as do organisation, supporting units, and whether defense or attack is rated "soft" or "hard". Technologies improve equipment, and army XP upgrades military doctrines. A more technologically advanced nation therefore often has an edge.

  A division that overwhelms an enemy province occupies it. Some provinces carry victory points, and holding them pushes a nation closer to capitulation. Occupying key provinces in a state gives the occupier access to that state's factories and natural resources. Where the occupier has no "core" on the territory it controls, resistance can hamper its grip.

  Nations with the proper technology can build nuclear bombs and use them to devastate enemy provinces and states. The update that came with the expansion Götterdämmerung added special projects. These need facilities to be built and cover nuclear energy and weapons, super-heavy tanks, intercontinental bombers and rockets. Armies are only one tool, because the same map is also crowded with alliances, pacts and rival ideologies.

  892386

• 4. Alliances and Ideologies

  ›

  The Comintern, the Chinese United Front, the American Commonwealth and the Greater East Asia Co-Prosperity Sphere are all factions in the game. The real Axis and Allies are split into many smaller factions like these for gameplay purposes. The American Commonwealth later joins the Allies. A player can create a faction or invite other nations into an existing one, and members may assist each other in wars. Other diplomatic actions include non-aggression pacts, guarantees of independence, and grants or requests for military access. Coups, war justification and ideological influence are available too. The expansion No Compromise, No Surrender brought faction goals, rules, research, military operations, intelligence, initiative and influence.

  Four ideologies shape every country: democratic, communist, fascist and non-aligned. Fascist nations can go to war easily, but other nations are less willing to trade with them. Democratic nations have difficulty invading others, yet they can guarantee independence with greater ease. A democracy may hold elections, which shift party popularity without spending political power. The non-aligned label covers monarchies, dictatorships and anarchies. If the German Reich opposes Hitler, the German Empire, a monarchy, can be brought back. If the anarchists win the Spanish Civil War, they are non-aligned as well. When another ideology grows too popular, a referendum can peacefully convert the nation. Otherwise ideologies take power through coups, civil wars or forced subjugation by a foreign power.

  The expansion Together for Victory introduced an autonomy system linking subjects and their overlords. Overlords can lower a subject's autonomy and annex it, while subjects can raise it and become independent. A points system drives this, influenced by Lend-Lease, building in the subject by the overlord, national spirits and more. Most countries use these autonomy types: Free, Dominion, Colony, Puppet, Integrated Puppet and Annexed. Later DLC added Reichskommissariats, personal unions, EU member states and Chinese warlord subjects. The expansion La Résistance added espionage in other nations and counterintelligence at home.

  A scale from 0 to 100 measures "world tension", the game's abstract picture of how close the world is to global war. Aggressive actions raise it and peaceful actions lower it. Depending on a nation's ideology and circumstances, a certain level of tension may be needed to justify a war or send volunteers to one. Even when tension allows it, a nation still has to decide how to spend its time, and the game answers with a tree of national focuses.

  1312243214

• 5. Focus Trees and Decisions

  ›

  For Germany to complete the national focus called Anschluss, it must first finish every focus that branches down to it. Each country has such a "focus tree", and the focuses on it can grant effects or trigger events. This system makes fixed, scripted events less necessary than in earlier installments of the series.

  Some rewards are tangible, like faster research for certain technologies or extra factories. Others, like better morale, are abstract, and the game represents them as "national spirits". Spirits can be temporary or permanent. Not every spirit comes from a focus, and not every spirit is entirely beneficial. Only one focus can be worked on at a time, and each one consumes some political power.

  At first, only a handful of key nations had unique focus trees: Nazi Germany, the United Kingdom, the Soviet Union and the United States. Every other nation shared a generic one. Later updates and DLC gave other countries trees of their own.

  Country events are pop-ups that focuses, decisions and other events can trigger, whether visible or hidden. Each event offers several options, often granting bonuses or penalties, such as choosing leaders in an election. Sometimes an event simply warns the player, for example that a civil war is about to begin. News events tell players when something of international significance happens.

  Decisions arrived with the update that coincided with the expansion Waking the Tiger. They let players choose policies without using the national focus slot. They often cost political power and cover propaganda, resource development, state integrations and country formations. Much of this was absent at the start, because the game kept growing through free updates and paid expansions.

  14291535

• 6. Release and Reviews

  ›

  Hearts of Iron IV was announced in 2014, with a late 2015 release originally planned. At E3 2015, creative director Johan Andersson confirmed the delay. The new target was the first quarter of 2016, an attempt to resolve several issues the game had encountered. In March 2016 it was announced that the game, built with the Clausewitz Engine, would launch on the 6th of June 2016. That date was the 72nd anniversary of the Normandy landings.

  More than 200,000 units sold within two weeks of launch. That made it the fastest-selling historically themed Paradox title up to that time, ahead of Crusader Kings II and Europa Universalis IV. Sales passed 500,000 in February 2017 and 1 million in May 2018. It was the first Hearts of Iron game to reach a million, and the third Paradox title to do so after those two. Metacritic's aggregate recorded "generally favorable reviews".

  GameSpot wrote that "Hearts of Iron IV embodies the hard truths about all-consuming war and the international politics that guide it." It called the tutorial the only weak point. Kotaku described the game as "overwhelming in both its depth and, more importantly, its complexity" and warned that newcomers might struggle with the interface.

  IGN called it "an incredibly complex World War II simulation that will require potentially hundreds of hours to master." It also said the payoff was brilliant for those willing to learn, and named it "a strong contender for the title of the ultimate armchair-general game." Its main complaints were almost all about performance. PC Gamer called it a "unique, beautiful, thrilling wargame". It praised the frontline system and production mechanics, but found the ideology system too bland and combat somewhat unintuitive.

  In 2022, six years after release and shortly after the By Blood Alone expansion, the game hit a concurrent player record of about 70,000. A week-long deal that made it temporarily free-to-play drove that peak. The previous year's record had been 68,000. As of November 2025, it has sold over seven million copies on Steam alone. Players who bought it in 2016 also received 17 major free updates and over 100 in total, which often coincided with paid expansions.

  416697071

• 7. Expansions and Packs

  ›

  Hearts of Iron IV has four kinds of DLC. Country packs add focus trees and other material for specific countries. Expansions do the same and also overhaul mechanics for every country. Focus packs concentrate on one country, and theater packs cover countries within a single theater of World War II. Some DLC is cosmetic, such as new armor models and music packs from a collaboration with the Swedish power metal band Sabaton.

  Together for Victory, released on the 15th of December 2016, was a country pack for Canada, Australia, New Zealand, South Africa and the British Raj. Death or Dishonor followed on the 14th of June 2017 with Yugoslavia, Romania, Czechoslovakia and Hungary, plus the ability to license military equipment. Waking the Tiger, on the 8th of March 2018, fleshed out the Second Sino-Japanese War. It covered Manchukuo, Nationalist and Communist China, and a shared tree for the warlords of Guangxi, Yunnan, Ma, Shanxi and Sinkiang.

  Man the Guns, released on the 28th of February 2019, brought a ship designer, government-in-exile mechanics and fuel as a resource separate from oil. It also added Netherlands and Mexico. La Résistance arrived on the 25th of February 2020 with a revamped France, including Free and Vichy France, a new tree for Portugal, and two for the sides of the Spanish Civil War. Battle for the Bosporus, on the 15th of October 2020, gave trees to Greece, Bulgaria and Turkey.

  No Step Back, released on the 23rd of November 2021, added railroads, armored trains, railway guns, a tank designer and a general staff. It also brought trees for the Baltic countries and a reworked one for the Soviet Union. By Blood Alone, on the 27th of September 2022, added a plane designer, unit medals and new peace conference options. Its new trees covered Switzerland, the Sultanate of Aussa and Ethiopia, with a reworked Italy. Arms Against Tyranny, on the 10th of October 2023, supplied trees for the Nordic countries and customizable special forces units. Trial of Allegiance, on the 7th of March 2024, covered Argentina, Brazil, Chile, Paraguay and Uruguay.

  Götterdämmerung, German for Twilight of the Gods, came out on the 14th of November 2024 and centers on military raids. It updated the trees for Germany and Hungary and added new ones for Austria, Belgium and the Congo. Its announcement introduced Expansion Passes, limited-time discounted bundles of upcoming DLC that end with the last included release. Graveyard of Empires followed on the 4th of March 2025 with Iran, Iraq and Afghanistan. No Compromise, No Surrender, on the 20th of November 2025, improved military doctrines and naval mechanics, and added trees for Japan, Nationalist China, Communist China and the Philippines.

  Peace For Our Time, released on the 22nd of April 2026, added a focus tree for Czechoslovakia. It was the first gameplay-changing DLC for the game to feature material created by modders. Thunder at our Gates was scheduled for the 11th of June 2026, with trees for Australia, Siam and the Dutch East Indies, plus military HQs and ship captains.

  Older DLC does not stay separate forever. On the 4th of April 2024, Together for Victory, Death or Dishonor and Waking the Tiger became part of the base game. On the 20th of November 2025, Man the Guns joined them when No Compromise, No Surrender launched.

  2426272930

• 8. Mods and Controversy

  ›

  According to game director Dan Lind, 64% of Hearts of Iron IV players use mods. The game was built to be more open-ended than earlier entries in the series, which made modding easier. Mods are found on Paradox Mods and the Steam Workshop. Many barely change the experience and have become community mainstays, like "Player-Led Peace Conferences", which gives the player more control over postwar peace conferences. Other mods are total conversions that rewrite the game through alternate history or new starting scenarios.

  Kaiserreich: Legacy of the Weltkrieg, first released on the 1st of December 2016, imagines a world where the Central Powers won World War I. Many community members consider it the largest and most in-depth mod. Old World Blues, whose legacy version appeared on the 17th of February 2018, is set in the Fallout universe and was praised for portraying that series within a grand strategy game. The New Order: Last Days of Europe is set in an alternate 1962 after an Axis victory in World War II. A three-way Cold War pits Nazi Germany, Imperial Japan and the United States against each other. It was first released on the 21st of July 2020, its modern version arrived on the 27th of March 2021, and it drew praise for rich storytelling and an esoteric atmosphere.

  Other mods have drawn controversy. Millennium Dawn lets players control any country in the modern day, including the Islamic State's caliphate. Deus Vult, now removed, let players control the Knights Templar and commit various atrocities.

  Critics have accused the game of contributing to political extremism, particularly with the rise of the alt-right. The Global Network on Extremism and Technology published a 2022 study of the subreddit r/HOI4. It found that a minority of posts espoused anti-semitic and Nazi-sympathetic views, but that these views were suppressed and most comments were apolitical.

  Kotaku reported that many mods attracted overtly racist, islamophobic, anti-semitic and hypernationalist comments. One mod writer told the outlet by email, "If there are Islamophobes among those who enjoy my mods, then that's how it is. I will not start a witch hunt against people who have different political views". Kotaku wrote that much of the vitriol stays up on free speech grounds, though some mods, such as Millennium Dawn, have actively removed particularly extremist views.

  On the 2nd of November 2017, China banned the game, shortly before the Waking the Tiger announcement, for "a claim that the game does not comply with local law." The ban came even though Tencent, a Chinese game developer, had bought 10% of Paradox Interactive on the 27th of May 2016. China had banned the earlier Hearts of Iron in 2004 for "distorting historical facts", citing its depiction of Tibet, Manchukuo and West Xinjiang as sovereign countries and of Japan controlling Taiwan.

  5657646680