Gameplay in Forged Alliance is largely the same as in the original Supreme Commander. The player uses a giant bipedal mech called an Armored Command Unit (or ACU) to build an army with which they can conquer their opponents. Forged Alliance expands on the original gameplay mechanics, adding new units, modifying old ones, and introducing other improvements to the user interface. The most notable addition to this expansion is the addition of a new faction, the Seraphim. In addition, the three original factions — the United Earth Federation (UEF), Cybran Nation, and Aeon Illuminate — also receive a number of new units. Other new content includes new maps. Several improvements to the controls and behind the scenes mechanics have been made as well. The interface has been revamped, as well as improved pathfinding and aircraft flight dynamics.