There are four military forces in the galaxy fighting in The Infinite War:
- The United Earth Federation
- The Cybran Nation
- The Aeon Illuminate
- The Seraphim (Forged Alliance only)
When playing Supreme Commander, a player selects one of the three factions, and they fight for that faction. This choice determines which units are available to the player. Although many of the factional units are identical or nearly identical, there are many faction differences, including units with different capabilities and different experimental units.
In Forged Alliance, the Seraphim are introduced as a playable race.