First things first - we're starting off with an introduction to the area before the arrival of the Vikings.

Pre-Viking Dublin

Whilst most attribute the foundation of Dublin to the Vikings, and indeed the city celebrated its millennium in 1988 CE, meaning that the government views 988 CE as the year of its foundation, an earlier date is more likely. 

The first potential mention of Dublin comes from the Roman cartographer Ptolemy who, in 140 CE, refers to a settlement called Eblana polis which is speculated to be Dublin. 

However, this is contested, and it is now thought that the first settlement was an Irish ecclesiastical center called Duiblinn, meaning "black pool," which refers to a dark tidal pool at the heart of the city. 

When the Vikings arrived and settled the area, they used this Gaelic name, calling their settlement Dyflin.

The foundation of Dyflin

Vikings first raided Ireland in 795 CE, but these raids were mostly restricted to the coastal and island areas. 

It would only be in the 820s that the scale of raids increased, inland areas were targeted, and specialized raiding encampments were created to allow armies to remain in Ireland for the winter. 

These were called longphuirt (sg. longphort) and formed the backbone of Norse settlement in Ireland. In 837 CE, sixty longships raided up the river Liffey that runs through Dublin and are likely to have raided the church site at Duiblinn.

Two contemporary sources place this raid as the first time the Vikings took land in Dublin, but this was only the beginning of Viking involvement in Dublin. 

The Viking control of Dublin is thought to have begun in 841 CE when the Norse seized the ecclesiastical settlement and established a longphort there, likely on the site of what is now Dublin Castle. 

This started the separation between the two parts of Dublin: Dyflin, controlled mostly by the Norse, and Áth Cliath, which saw more native settlement, at least in the early years of the settlement. 

It has also been hypothesized that a longphort was established at Áth Cliath as well. Using Dublin as a strong base for the winter, the Vikings were able to strike deeper into Ireland and establish more longphuirt

In the mid-9th century CE, the Norse experienced multiple setbacks in Dublin. Photo: Cristian N Gaitan / Shutterstock

But it was not smooth sailing for the Norse in Dublin after this. In the late 840s CE, the Vikings suffered a number of defeats, and the legendary Irish High King Máel Sechnaill plundered and temporarily destroyed the Norse settlement at Dublin, which led to retaliation by a huge Irish fleet. 

This started a period of decline for Dublin, wherein a mysterious group of Norsemen called Dubgaill continued to raid Dublin and inflict casualties on both the native Irish and the Norse settlers of Dublin called the Findgaill.

These two Norse factions would dominate the Irish Sea for the rest of the 9th century CE and would oversee the establishment of the Kingdom of Dublin. 

This first kingdom would be founded by the Viking warlord Óláfr in 853 and would be used by him and his brothers, which included the famous Viking Ivar the Boneless, as a base for their raids and invasions of the British Isles. 

Dynastic troubles and ambitions in England weakened this kingdom of Dublin, and the Norse were eventually driven out of Dublin yet again by the native Irish in 902, ending the first kingdom and destroying the city. 

The re-establishment of the kingdom

The Norse would not stay away for long, and in 917 CE, a new Norse kingdom was founded in Dublin by Sitric Cáech, according to Winroth's 2016 work The Age of the Vikings

His kingdom would survive for longer than the first and would hold great sway both in Ireland and across the sea in England, where some of his descendants would control the kingdom of Northumbria before its conquest by the house of Wessex. 

There would be a setback in 1014 CE when the High King Brian Boru defeated the Norse, and the kingdom would be limited in its political exploits and would stick to trading and minor raiding. 

The economy of Viking Dublin revolved mostly around slavery, and its position in the Irish Sea allowed for the exploitation of much of the coast of the British Isles for this purpose. 

This kingdom would last until the late 12th century CE, when it would be conquered first by the Irish and then by Anglo-Norman kings, beginning the period of English control of Dublin.

Dublin was an extremely important Viking hub that had remarkable longevity. It was a melting pot of cultures from across the British Isles and beyond and hosted some of the greatest names from the Viking Age. 

Its Viking legacy is seen in its name, its streets, its people, and the city's prominence throughout history. 

You can find out more about the first volume of the Irish government's history of Dublin Castle here.

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