Hearts of Iron is a strategy game that covers the II World War period at a theaterwide level. Unlike the majority of WW2 games, it focus on global strategy and not on tactical aspects. You play the role of any nation present on the period (not only the major powers of the Axis, Allies or the Komintern), and struggle to make your path over that turbulent years; not only the time of war, but also the years of pre-war (1936-1939), when tensions ran high and hostilities were soon to break out.

The game presents several scenarios that cover different time intervals, allowing you to choose between preparing for battle or starting in the middle of the affair. Also, the game includes a strong scenario editor to make the situation fit your preferences. Although the game is real-time, you can set the time flow and pause if you wish.

The final objective in the game is to make your ideology (Fascism, Communism or Democracy) the most extended in the world, and you do so, obviously, by the force of arms, but also making use of political influence and domination. On the road to victory, you have to pay attention to countless factors: industrial capacity, population support and discomfort, supplies, raw materials, convoys, weather, politics and diplomacy, including a huge technology tree and managing your own Cabinet from an also huge array of ministers and officers with their own motivations and personalities. Also, many historical and random events play their role in the outcome of each game.

The game has a strong board-like feeling, with the world divided into countries, and the countries into provinces, which are the "tiles" where action takes place. Each province has its own value, both material and of manpower capacity.

The game follows the path of the Europa Universalis Serie:, and so shares many similarities with it.