Liberating Europe, Russian and the Pacific Islands or... fending off the hated Allies and conquering them, you chose. An old turn based game that can even give you some nasty grief when playing against the AI. It also has recreated historical battles and lots of good units from the entire war. You can mod the crud out of it and I've even found out how to change the leaders and troop/equipment graphics.
Oh, it's Talonsofts Western Front, Astarte Front and Rising Sun games.