Hearts of Iron 2

From the paradoxplaza.com webpage:

Hearts of Iron 2 is the sequel to the most appreciated World War II PC game of true Grand Strategic scope ever made. As in its forbear, the map spans the entire world and allows you to play one of over 175 countries during the course of World War II. The game is completely revised with an updated combat system, a new map, revised and easy-to-use interface, new technology tree and hundreds of other updates and improvements.

Main features:

  • Re-designed user interface enhancing the player experience as well as deepening the game play
  • Detailed diplomacy and production systems with help functions to avoid micromanagement
  • "Movement-is-attack" combat system making warfare more realistic
  • Mission-based Air and Naval system, giving options for logistical strikes and targeted bombing
  • New political system with possibilities to change the political base of your country during the war
  • Fifteen battle scenarios optimized for an evening or two for gaming. Historical scenarios like Case White, Operation Barbarossa and alternative history scenarios like Operation Watchtower and Case Green are included in the game.
  • Co-operative multiplayer, enabling players to share the same country while playing