Vikings in Iberia
The first incursion of the Vikings in Iberia has been characterised as 'probably the most significant episode of the whole period of Viking activity in the South'. It is mentioned in "Annales Bertiniani", and dated August 844, when a group from a plundering expedition entered the Garonne and reached Galicia. Despite storm damage, some proceeded to South-West Spain. This account is consistent with several later, but independent sources in Latin and Arabic. In particular, the late ninth- or early tenth-century "Chronicle of Alfonso III" adds that after plundering a number of coastal villages they were ultimately repulsed in the vicinity of "Farum Brecantium" (i.e. the Tower of Hercules). Ramiro I of Asturias gathered troops in Galicia and Asturia for the counter-attack. After the Asturian victory, the Vikings continued their voyage in direction of Lisbon. While some authors consider that the reliability of this chronicle is open to doubt, others consider that other local chronicles confirm the arrival of the Norsemen.
History of Limerick
The earliest record of vikings at Limerick is in 845, reported by the "Annals of Ulster", and there are intermittent reports of vikings in the region later in the 9th century. Permanent settlement on the site of modern Limerick had begun by 922. In that year a Viking jarl or prince called Tomrair mac Ailchi—Thórir Helgason—led the Limerick fleet on raids along the River Shannon, from the lake of Lough Derg to the lake of Lough Ree, pillaging ecclesiastical settlements. Two years later, the Dublin vikings led by Gofraid ua Ímair attacked Limerick, but were driven off. The war between Dublin and Limerick continued until 937 when the Dubliners, now led by Gofraid's son Amlaíb, captured Limerick's king Amlaíb Cenncairech and for some reason destroyed his fleet. However, no battle is actually recorded and so a traditional interpretation has been that Amlaíb mac Gofraid was actually recruiting Amlaíb of Limerick for his upcoming conflict with Athelstan of England, which would turn out be the famous Battle of Brunanburh. The 920s and 930s are regarded as the height of Norse power in Ireland and only Limerick rivalled Dublin during this time.