Hearts of Iron IV

Lore & Background

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, with start dates on 1 January 1936 or 14 August 1939 in single-player or multiplayer. The game features an economy system where military factories produce equipment, dockyards build ships, and civilian factories construct buildings, produce consumer goods, and oversee trade. Since the update coinciding with the expansion No Compromise, No Surrender, all factories need to be powered by coal, with power gain influenced by technologies and buildings such as dams or nuclear power plants. With the expansion Arms Against Tyranny, the player can interact with the global arms market and access military industrial organizations, which improve military equipment over time.

Reader's Guide

Hearts of Iron IV is notable for its detailed simulation of World War II grand strategy, with a focus on economic management, military customization, and complex diplomacy. The game includes a national focus system that reduces reliance on scripted events, and a world tension mechanic that measures global aggression. The expansion Together for Victory introduced an autonomy system for subjects and overlords, while La Résistance added espionage and counterintelligence. The game has sold over seven million copies on Steam alone as of November 2025, and Paradox has released a large amount of downloadable content since its release. Its significance lies in its depth of gameplay, allowing players to control any nation and pursue historical or alternate paths, with a strong emphasis on player choice and strategic decision-making.

Did You Know?

• Hearts of Iron IV is the fourth main installment in the Hearts of Iron series.
• The game sold one and a half million copies worldwide by May 2018.
• The expansion No Compromise, No Surrender introduced coal as a resource for powering factories.

Military Command & Combat Depth

Hearts of Iron IV places the player at the helm of a nation's full military apparatus, spanning ground, naval, and aerial forces. Ground armies are built from divisions that the player assembles from infantry, tanks, cavalry, motorized, and mechanized battalions, each demanding both equipment and manpower to function effectively. The battlefield is broken into tiny provinces grouped into states, with each province carrying its own terrain and weather modifiers that influence how well different unit types perform. Combat outcomes hinge on a web of interacting variables: equipment quality, the commanding general's skill and traits, aerial superiority in the region, supply-line integrity, division organization, and the balance of soft versus hard attack and defense. Military doctrines, upgraded through army experience, can tilt the scales in favor of technologically advanced nations. When a division overwhelms an enemy province, it occupies the territory; capturing victory-point provinces pushes the defender toward capitulation, while seizing key provinces within a state unlocks the enemy's factories and resources. Resistance from occupied populations lacking a core can further complicate control. Nations that unlock the proper technology can even develop nuclear bombs to devastate enemy territory.

Industrial Economy & Political Power

The economic backbone of Hearts of Iron IV rests on a layered factory system. Civilian factories serve as the foundational resource: they build military factories and dockyards, produce consumer goods for the population, and manage international trade. At the start of a campaign, most nations must dedicate a large share of their civilian capacity to consumer goods, but as mobilization progresses, more factories are freed for military production. Since the No Compromise, No Surrender expansion, every factory requires coal to operate, and the efficiency of that power supply can be shaped by technologies and state-level buildings such as dams or nuclear power plants. The Arms Against Tyranny expansion added a global arms market and military industrial organizations that gradually improve equipment quality over time. Overseeing all of this is political power, an abstract resource the player spends to adjust mobilization levels, conscription rates, and trade laws, as well as to appoint ministers and reshape the nation's government. This interplay between industrial planning and political decision-making gives the economic layer a persistent strategic weight throughout a campaign.

Diplomacy, Factions & Ideological Identity

Beyond the battlefield, Hearts of Iron IV recreates the intricate diplomatic landscape of the late 1930s. Nations can sign non-aggression pacts, guarantee another country's independence, grant or request military access, execute coups, justify wars, and pressure other states to adopt their ideology. A central diplomatic mechanic is the faction system: real-world blocs like the Axis and Allies are broken into numerous smaller factions, including the Comintern, the Chinese United Front, the American Commonwealth (which later merges into the Allies), and the Greater East Asia Co-Prosperity Sphere. Faction members can aid one another in wars, making alliances strategically vital. The No Compromise, No Surrender expansion deepened faction play with goals, internal rules, shared research, joint military operations, intelligence sharing, initiative, and influence. Every nation in the game also carries one of four ideologies—democratic, communist, fascist, or non-aligned—each with distinct mechanical trade-offs. For instance, fascist states find it easier to declare war, while other ideologies offer different strategic advantages and constraints.

Commercial Longevity & the DLC Ecosystem

Hearts of Iron IV has demonstrated remarkable commercial staying power since its 2016 launch. By May 2018, the title had moved one and a half million copies worldwide. By November 2025, sales on Steam alone had surpassed seven million, a figure that speaks to the game's sustained appeal nearly a decade after its debut. A major driver of that longevity is Paradox Interactive's prolific downloadable content strategy. The studio has shipped a large volume of expansions and updates that meaningfully reshape the gameplay experience. The No Compromise, No Surrender expansion overhauled faction mechanics and introduced the coal-powered factory requirement. Arms Against Tyranny added the global arms market and military industrial organizations. Götterdämmerung brought special projects that demand dedicated facilities for nuclear energy, super-heavy tanks, intercontinental bombers, and rockets. Together, these additions keep the strategic landscape evolving and give returning players fresh systems to master, helping the title maintain an active community far beyond its initial release window.