The suggested reasons for the appearance of the Vikings at the end of the 8th century in Scandinavia are varied. The most logical explanation to date is the possible overpopulation of the region. An explosion in Nordic population throughout Norway, Sweden, Finland, and Denmark during the 7th and 8th centuries may have forced the indigenous people to explore and settle in more favorable territories. In addition, the gradual establishment of government throughout most of Western Europe augmented mercantile trade greatly as well as the opportunities for piracy. At home, these Scandinavians were independent farmers, but at sea or on the fields of war they were some of the fiercest warriors in the world.

The Scandinavian art of shipbuilding evolved during the course of the 8th century and greatly facilitated these early Viking expeditions and raids. The most distinct differences between the Viking ships and their merchant vessel victims, was that the merchant ships were short, broad and relied on sail power, while Viking warships were longer, thinner and had a far greater number of oars and men. This made the Viking ships notably faster, and was instrumental in allowing the Vikings to penetrate long distances up rivers. Small armies of Viking longships negotiated the seas, utilizing hit-and-run tactics on the cities, towns, and villages that dotted the coasts of Europe. These longships were the very tools of Viking expansion. The Vikings were able to raid far afield and subsequently colonize the lands that they plundered.

Viking hordes attacked England at the end of the 8th century, after which followed a period of relative calm that was shattered years later when attacks began renewed. At first, the Vikings led nothing more than predatory aids in the summer months in search of booty and slaves, with no attempts permanent settlement. Beginning in 850 however, there appeared to be changes in Viking strategy, for the first time, Vikings occupied entire villages and regions in the winters following their raids… they had come to stay.

In 865 a massive fleet arrived that carried some of the fiercest Viking leaders, including sons of the Danish King Ragnar Lodbrok ("Hairy-Breeches"), whose family was regarded as representing the very epitome of true Vikings. Ivar the Boneless, Halfdan, and Ubbi (or 'Hubba') brought military ambitions with them. Ragnar's sons captured York at the end of 867; and then proceeded to overrun most of Northumbria, Anglia, and Mercia. Ivar advanced to Dublin to conquer it, later dying in the Battle of Ashdown in 871. Halfdan became the chief leader following Ivar, where he defeated the English at Basing, Meretun, Reading, and Wilton. For the next few years the Vikings concentrated on securing conquests in eastern and northern England. They divided Northumbria and Mercia amongst themselves, and Halfdan followed in Ivar's footsteps in another attempt to secure Dublin from Ireland, only to be defeated by Norwegian Vikings in 877.

The Scandinavian countries seemed to possess an inexhaustible supply of able-bodied warriors and manpower. In land battles Vikings favored overlapping shield-wall formations, which consisted of approximately 5 or more ranks deep of the most heavily armed and armored Vikings forming the exterior of a line, wedge, or circle formation to absorb the brunt of enemy attacks. In the pagan era, before Scandinavia was converted to Christianity, the berserkir warriors were looked upon as possessing supernatural powers attributed to the Viking's chief god, Odin; and a belief in lycanthropy. These warriors were known to rush into battle without armor, as mad as wolves, and as strong as wild boars. This infamous berserkir frenzy reportedly allowed them to kill men in single blows with great bearded axes, and shrug off blows from fire and iron alike. Today it is believed that these frenzies were the result of epileptic attacks.

The era of the Viking lasted only 300 years, ending at approximately 1066AD; around the time of the approximated death of Harald Hardrada, who died heroically in battle. Harald has been dubbed 'the last Viking'. Most remaining Viking conquests and exploits never amounted to those of their predecessors, and Viking lineage gradually integrated into their surrounding civilizations.

In Civilization III: Play the World, the Vikings are considered a Militaristic and Expansionist civilization, therefore, they start with Pottery and Warrior Code and have significant bonuses to exploratory and military activities. See the developer update on Civ-specific abilities for more on these bonuses.

Unique Unit: The Berserk

In the pagan era, before Scandinavia was converted to Christianity, the berserkir warriors were looked upon as possessing supernatural powers attributed to the Viking's chief god, Odin and a belief in lycanthropy. These warriors were known to rush into battle without armor, as mad as wolves, and as strong as wild boars. This infamous berserkir frenzy reportedly allowed them to kill men in single blows with great bearded axes and shrug off blows from fire and iron alike. Today it is believed that these frenzies were the result of epileptic attacks.

The Berserk replaces Longbowmen for the Viking civilization. In addition to being formidable foot soldiers, berserkir are one of the first available amphibious units in the game, which allows them to attack enemy units or structures directly from within sea-based transport vessels.