The game contains many unique and innovative features, including a well implemented "morale" system which directly affects individual units statistics.It also incorperates a "hero" system, which has a special unit with extraordanary combat ability which can either heal nearby units or demoralise enemy units. It also incorperates the system of "Fortresses", which allow you to store units which do not count to the population units for release when needed
Empire Earth has an expansion called "Empire Earth: The Art of Conquest". AOC features a 15th epoch, the Space Age, along with several special powers for building civilizations, including Priest Towers (convert enemy units into your own) and Just-In-Time Manufacturing (create units immediately for a higher resource cost).