In
Hearts of Iron III, you play as the leader of a country during WWII and play through events beginning in 1935 and ending in 1947. Every nation that participated in the war is available, as well as a few smaller countries. Playing as the larger countries yields bigger bonuses, but it's fun and more interesting to take a smaller country and make a global splash.
As hinted at earlier, gameplay primarily involves combing through menus and maps in order to move your nation's plans forward. At home, you'll manage your war-time economy and research new technology to help give you an edge, while abroad you'll order troops, develop diplomatic alliances with other countries, move troops and even participate in a little espionage against enemies. In short, there's a lot to do and Hearts of Iron III does a good job at making the information relevant and easy to get to.
Hearts of Iron III may lead to a few fantastic situations, but the game manages to cling close to historic accuracy. Countries start out in more or less the exact situation they were in at the start of the war. You'll see a number of well-known political faces as well as era-accurate technology and politics. It's amazing how much Paradox was able to squeeze into the game without it buckling under its own weight or becoming too much like an interactive documentary. There's also an organic sense of unity running through all of the game's systems. For instance, if you use a certain unit type often, research and development will go much quicker for related tech trees.