Medieval: Total War - Viking Invasion is an expansion for Medieval: Total War. It features a new campaign map of the British & Irish Isles along with Scandinavia, and starts the game in an earlier period of history (the main game runs from 1087 to 1453, while the British & Irish Isles campaign of the expansion runs from 793 to 1066). Players can either try to unite the people of the British & Irish Isles, or simply conduct raids on coastal settlements by taking on the role of the Viking invaders. The existing Europe-Near East campaign is also expanded with new units, and three formerly unplayable factions are made available to the player. Another feature of VI is the addition of more playable factions, one of which is the Aragonese.
The major difference between MTW and VI is a bug (termed "swipe" by players) that was fixed in the expansion pack. This bug allows players to give their cavalry unlimited charging bonus if utilized.