"Hearts of Iron is a grand strategy computer game developed by Paradox Interactive and published by Strategy First, set in the years 1936-1948. In the game you can control any one nation as World War II unfolds. It was released for Windows-compatible PCs in 2002.
Hearts of Iron is based on Paradox's successful Europa Universalis game engine, but has many changes:
* a tech tree divided into 14 sections (infantry/artillery/industry/armoured units/navy/etc.), with dozens of researchable technologies in each section and the ability to customize some units.
* an economic model based on four natural resources: coal, steel, rubber and oil on which the armed forces and industry depend.
* Several military and political leaders to choose from.
* A variety of military units, from colonial militia to ICBMs.
* A weather model, affecting movement and combat efficiency of units.
Gameplay revolves around surviving (either before or during) World War II, and the player may cause or witness events different from how they historically occurred. Hearts of Iron is considered an alternate history game.
There are three main alliances in the game, the Allies, the Axis, and the Communist International that the player can either participate in or stay out of. The game ends when there is only one alliance left standing or on midnight, December 30, 1947, and the winning alliance is determined through a victory point system, giving points to alliances controlling key regions or cities.
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Source: Wikipedia, "Hearts_of_iron," available under the CC-BY-SA License.