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.
Ólchobar mac Cináeda
Late in 848 Ólchobar is said to have set up a camp from which the Vikings at Cork were blockaded. The result of this siege is nowhere recorded. This is the first mention of the Vikings at Cork. They are not heard of again until 865. It has been suggested that these several campaigns against Vikings were a coordinated effort by the chief Irish kings.