The Vikings, aristocratic Scandinavians, were great sailors and ruthless warriors who travelled in well-built longships. They began to raid the coasts of Ireland, Britain and France in the AD 790s. The island-based monasteries were particularly vulnerable to attack and made rewarding targets for the fast-moving raiders.
This random raiding persisted for several decades, gradually intensifying until it became a concerted campaign by the end of the AD 830s, by which time the Vikings had established bases at Annagassan in County Louth and, more importantly, at Dublin.
Then, however, just when it seemed as though they were on the point of overrunning the country, several of the Irish kings managed to hit back at them and contain the threat. The crisis subsided and the Vikings withdrew to consolidate their positions at Dublin, Wexford, Waterford and Youghal.
These Viking settlements merged into the mosaic of small kingdoms that covered Ireland. They played their part in the regular local power struggles until, in AD 914, the arrival of a huge Viking fleet in Waterford marked the start of a new campaign. The Vikings attacked Munster and Leinster, defeated the Ui Neills and their allies who had marched southwards against them, and greatly consolidated their position.
The Viking age in Ireland ended early in the eleventh century. During the first phase, the Vikings generally raided Irish monasteries and returned to Scandinavia with their booty. They took part in internal Irish wars and made Ireland a centre of European trad. They also introduced the use of money and had a great influence on art, language, folklore and place names.