When did the Vikings arrive in Ireland?
Auisle
The earliest recorded Viking raids in Ireland occurred in 795. Over time, these raids increased in intensity, and they overwintered in Ireland for the first time in 840–841. Later in 841 a longphort was constructed at Áth Cliath (Irish for "hurdled ford"), a site which would later develop into the city of Dublin. Longphorts were also established at other sites around Ireland, some of which developed into larger Viking settlements over time. The Viking population in Ireland was boosted in 851 with the arrival of a large group known as "dark foreigners" – a contentious term usually considered to mean the newly arrived Vikings, as opposed to the "fair foreigners", i.e. the Viking population which was resident in arrival prior to this influx. A kingdom in Viking Scotland was established by the mid ninth-century, and it exerted control over some of the Vikings in Ireland. By 853 a separate kingdom of Dublin had been set up which claimed control over all the Vikings in Ireland.
Longphort
The word was first used in the 840s in the Irish account of The Annals of Ulster and in the Frankish account in the Annals of St. Bertin with the establishment of Viking encampments at Linn Duachaill and Dublin. It also describes new Viking settlements established at Waterford in 914 and Limerick in 922 possibly by the Uí Ímair. Many camps along river banks and lakes did not last long, however, some only as little as one or two seasons, but others such as Dublin developed into large urban centers, as did the other significant Norse settlements at Cork, Waterford, Wexford and Limerick which remain the largest urban centers in Ireland today.