From the Paradox Interactive site:

Hearts of Iron is the first ever World War II PC game of true Grand Strategic scope. The game map spans the entire world and allows players to take the War to any new front of their choosing. Any nation in the world is playable, but the game focuses on the epic struggle between the great alliances of the new world orders Fascism, Communism and Democracy.

Hearts of Iron is developed by the team behind the award winning sales success Europa Universalis I and II and brings the same super detail to a modern day gaming experience.

Hearts of Iron aims to be no less than the definitive World War II strategic experience.