Faction
A Faction in the context of the Total War series of games refers to one of the various competing forces which may or may not be controllable by the player when starting a campaign or custom battle. During any campaign or custom battle, the player may choose one faction to play as while the remaining active factions will be controlled by the computer, or another human player in the case of multiplayer matches. When the computer controls a faction it will simulate the moves a human player would be likely to make in order to provide a challenge based on the selected difficulty. In the game Medieval 2: Total War playable factions from the start include England and France, with more factions becoming unlocked as the game continues.
Many mods alter the vanilla version of the Total War games to add customised or entirely new factions for players to take control of during campaigns.