North Germanic peoples
Vikings were also active in Francia. Some of these Vikings would sail through the Strait of Gibraltar and pillage the coasts of the Mediterranean Sea. In the early 10th century, a group of Vikings under the leadership of Rollo settled in Rouen, France, and established the Duchy of Normandy. The descendants of these Vikings, known as the "Normans", would in the 11th century conquer England, Southern Italy, and North Africa, and play a leading role in launching the Crusades. Sub-groups of the Normans include Anglo-Normans, Scoto-Normans, Cambro-Normans, Hiberno-Normans and Italo-Normans.
Kingdom of Dublin
Vikings invaded the territory around Dublin in the 9th century, establishing the Norse Kingdom of Dublin, the earliest and longest-lasting Norse kingdom in Ireland. Its territory corresponded to most of present-day County Dublin. The Norse referred to the kingdom as "Dyflin", which is derived . The first reference to the Vikings comes from the "Annals of Ulster" and the first entry for 841 CE reads: "Pagans still on Lough Neagh". It is from this date onward that historians get references to ship fortresses or longphorts being established in Ireland. It may be safe to assume that the Vikings first over-wintered in 840–841 CE. The actual location of the longphort of Dublin is still a hotly debated issue. Norse rulers of Dublin were often co-kings, and occasionally also Kings of Jórvík in what is now Yorkshire. Under their rule, Dublin became the biggest slave port in Western Europe.