The Viking history of Ireland: A primer

First raiding and then settling along coastal towns, including Dublin, Cork, and Limerick, Ireland's formative history owes much to these Viking warriors and settlers.

Early beginnings  and lightning raids

Just a few years after the raid on Lindisfarne off the northeast coast of England that traditionally signals the start of the "Viking Age" (approx. 793 – 1066 CE), Viking warriors invaded the island of Ireland. In fact, the Vikings' conquest of Ireland would set about a blueprint for further Norse expansion in the following two centuries. Before the Vikings arrived, the majority of people in Ireland lived in small and scattered communities. After the Vikings, the cities of Dublin, Cork, and Limerick had all begun on their journey of establishment.

In 795 CE, a Viking raid took place on the island of Reachrainn (Lambay Island), a few kilometers offshore from what is now modern Dublin. During this raid, a church was ransacked and burned. Further lighting raids took place both in the surrounding areas, in Brega (798 CE) and further abroad, in Connacht (807 CE).

These Viking raids would end a period of cultural flourishing for Ireland and plunge the island into more than two hundred years of invasions, subjugation, civil war, and social upheaval.

Longports and settlement

In the early 9th century, political certainty and structure under Áed Oirdnide, the High King of Ireland, made it hard for the Vikings to raid along the Irish coast. However, divisions within the various Gaelic kingdoms and clans took place during the latter years of his life, weakening his kingdom's political and security situation. This uncertainty and political rivalry between clans were exploited by the Vikings following Oirdnide's death in 819 CE.

From the 820s CE onwards, Viking raiding returned with a renewed intensity along the Irish coast. The first longports (a Viking ship enclosure or a fortification) were established to allow Viking warriors to winter in Ireland instead of returning to their Nordic or British bases. The first such longports were established at Linn Dúachaill (Annagassan), and one was centered on the River Liffey, called Duiblinn (Dublin). These allowed Viking raiding parties to increase in size, with as many as 1,500 men, to target the larger monastic towns from Armagh to Slane and Kildare.

Historical records and power struggles

One of the most important sources available for this period of Irish history is the Annals of the Four Masters. These epic chronicles, covering Irish history from the Biblical deluge until the early 17th-century CE (a mere 2,000+ years in scope), were collated in the Irish language from multiple earlier sources, with a large focus on the early medieval history of Ireland.

The growing influence of Vikings in Irish society is mentioned in the Annals from the mid-9th century onwards. The first Viking to be specifically named is Thorgest, who was said to have led a raid on a church at Clonmacnoise in 844 CE. However, anti-Norse and anti-pagan biases are evident in the Annals' descriptions of Vikings in general. Thorgest is portrayed as little more than a cartoon-esque villain, with his wife described as a witch who undertook sacrilegious (to the Christian writers) pagan rituals. Nonetheless, the Annals are a fascinating glimpse into the (biased) history of Ireland during the early Viking settlements.

During the mid-9th century, the growing Viking presence is met with some resistance. A Norse army was defeated in 848 CE by combined forces of the King of Munster and the King of Leinster. However, this would matter little as the Vikings would then defeat the High King of Ireland, Máel Sechnaill, at Forrach later in the year. This would lay the groundwork for the establishment of a Viking dynasty, Uí Ímair (the Ivar Dynasty), which was, according to the Annals, founded by Viking warriors Olaf the White and Ivar the Boneless in the early 850s CE.

Political situation in Ireland and the struggle for power

The Vikings were able to exploit internal divisions and rivalries in Anglo-Saxon England and the Frankish realms due to their high level of centralization. However, Ireland was different. It was a highly fragmented and decentralized polity with more than 150 different kingdoms spread across the island, ruling over small territories. This made it hard for the Vikings to make inroads to subdue all the numerous political elites across Ireland.

During the latter part of the 9th century, Vikings still managed to exploit some political divisions. However, they soon began to make political alliances with local rulers. During the reigns of Olav and Ivar, they were unable to subdue the kingdoms in the far north of the island, focusing their rule on the establishment of settlements further south. In 902 CE, however, the rulers of Brega and Leinster entered a military alliance to force the Vikings out of Dublin…temporarily.

In 902 CE, the rulers of Brega and Leinster entered an alliance to force the Vikings out of Dublin…temporarily. Photo: Soff Garavano Puw / Unsplash

The Norse Gaels and local uprisings

Following a decade-long hiatus of Viking settlement in Ireland, longships began again to appear off the Irish coast from 914 CE. This signaled the second phase of Viking rule in Ireland. Over the next decade, the Vikings established settlements further south of Dublin, in Cork, Limerick, Waterford, and Wexford. They over-intermingled, married, and interbred with the local Gaelic population, producing what historians and academics call the "Norse Gaels." A Scandinavian elite still ruled and held political power, but most of the inhabitants of these settlements were indigenous Irish.

With memories of driving the Vikings once out of Ireland still in local memories, further rebellions and uprisings began to take place, though the Vikings still proved their superior martial skills. A local uprising led by Niall Glúndub culminated in the Battle of Islandbridge in 919 CE. This was not only a decisive victory for the Vikings but also saw Niall and five of his fellow kings slain in battle. Over the course of the 10th century, more and more uprisings by local elites took place. Cnogan, the High King of Ireland, managed to sack Dublin in 944 CE, putting a dent in the perceived invincibility and superiority of Viking rule in Ireland.

The Battle of Clontarf and the end of Viking rule?

The dawn of the 11th century saw the political situation weaken for the Vikings in Ireland. A new King of Munster, Brian Boru, was appointed in 976 CE. He was on a mission to decisively defeat the Vikings in Ireland. 

He smashed the Norse warriors at Limerick (977 CE) and had received submission from every political ruler and king in Ireland by 1011 CE. He is widely acknowledged by historians as being the first proper "King of Ireland." However, the Vikings still held on to power, and their local allies rebelled, in Leinster and Dublin, against Brian's overlordship. This culminated in the Battle of Clontarf on Good Friday, 1014 CE.

Traditionally, the Battle of Clontarf has been portrayed as a fight for the sovereignty of Ireland between Irish forces, under Brian Boru, and Norse Vikings. However, renewed research had downplayed the significance of this battle. Nonetheless, Boru's forces did defeat the Viking, though Brian himself perished in battle along with an estimated 7,000 – 10,000 men. The Viking power in Ireland had been fatally damaged and broken following this battle. Regardless of its actual importance to the end of Viking rule in Ireland, it still holds a popular place in Irish imagination to this day.

The end of Viking rule and their influence in Ireland today

The decades following the Battle of Clontarf saw a decline in Viking power and rule in Ireland. Eventually, the Norman invasion of Ireland, from 1169 CE, would replace the Norse-Gael elite and influence. Henry II of England would invade Ireland and take Dublin in 1171 CE, creating the "Lordship of Ireland," which would last until the mid-16th century as part of the English crown.

The influence of the Vikings is still very much present in Ireland today. One of the most famous cathedrals in Ireland, north or south, is the Christ Church Cathedral in Dublin. A Norse ruler of Dublin, Sigtryggar Silkiskegg, was responsible for the start of construction of this cathedral in 1030 CE. Researchers at Trinity College, Dublin, have also recently found 23 new genetic clusters in Ireland believed to be linked to the Viking invasions of Ireland.

Finally, some common Irish surnames have their roots in the Viking era. McAuliffe (Son of Olav), MacManus (Son of Manus), and Doyle (Son of the dark foreigner) can all trace their meaning back to the time of the Vikings and the Norse Gaels.

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