Hearts of Iron IV is the sequel to Paradox Development Studio's game Hearts of Iron 3.
It covers the time period from 1936 to 1948, focusing on the buildup to the Second World War and the war itself.

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National unity

A measure of the war-resolve of the country. When fighting a war against a country with low National Unity, less conquered territory is needed to force the country to surrender than would be required if it had high National Unity. National Unity is determined by national spirit traits that can be assigned to certain countries in a scenario (France, for example, starts with very low NU), but it can be modified through national focus choices or recruiting government officials to modify it. National Unity also determines (along with Party popularity) how successful a staged coup d'├ętat is. The lower National Unity the target country has, the more states will rebel.

Political power

This is the amount of political capital the national leadership has accumulated. Political power is spent on completing national focus ideas, recruiting military and scientific advisers, changing trade and conscription laws, and executing some diplomatic actions. Each nation gets 2 points of political power per day, modified by certain traits, individuals, player actions or characteristics.


The number of men currently available to create and reinforce military units. This is affected by a number of factors, primarily conscription levels and number of units under construction along with casualties suffered. Manpower can be modified by altering a country's conscription laws and to some extent by occupying and annexing territory from other countries.

Army, Navy and Air experience

As units fight (or, in the case of armies, exercise) they gain experience. Army experience can be spent in the unit designer to edit or create land division designs. Naval and air experience are used for modifications to ship and plane designs, giving them bonuses to speed, firepower, reliability and so on (subject to trade-offs).


The number of convoys or transports available. Each trade for strategic resources will require allocating a convoy unit. Moving land units across oceans and seas also requires an allocation of convoys for transport. The number of available transports can be increased by building new convoys in the unit production menu.

First Expansion