Robots replace Citizens in the Nano Age and infantry in the Space Age (these robots are known as Watchmen). The new Space Age (Epoch XV) allows the building of spaceports and spaceships on maps that allow it. Online multiplayer capabilities has been added, allowing players to play online with up to 7 other players either over the internet via a lobby system, or over a local area network (LAN). Variable difficulty has been added to those scenarios which had not received it in a patch of the original Empire Earth. The gameplay in The Art of Conquest is the same as in the original Empire Earth, albeit with some changes. The Art of Conquest also features three new campaigns: Ancient Rome, World War II, and 24th Century Mars. The Art of Conquest added several new features to the original Empire Earth, including new units, new civilizations ( Japan and Korea), civilization powers, and new hero units.
