The player controls virtually every aspect of their country, including production, research, diplomacy, warfare, politics.

[4] The first trailer from the Games Convention in Leipzig showed new features such as 3D graphics, possible due to the new Clausewitz Engine.

[7] Although happy with the scope of Hearts of Iron II, lead designer Johan Andersson wanted to improve upon every aspect of the game, starting again with a new engine.

[8] The game's artificial intelligence (AI) was designed to be able to achieve strategic objectives and control forces delegated to it, including whole theatres of operation.

[9] Changing to 3D graphics helped improve other areas, as Andersson explained: Going 3D meant we could do another type of architecture where we could support more screen resolutions, and develop our maps in a quicker way.

[11] Hearts of Iron III initially received a mixed reception because the game shipped with a large number of bugs in the early release.

[18] After several patches eliminated many bugs, reception improved and the game received generally positive reviews.

[27] On 6 June 2012, Paradox Interactive announced the third and last expansion called Hearts of Iron III: Their Finest Hour.