Siege of Dumbarton
Who Fought
History & Significance
The siege of Dumbarton was a successful four-month siege of the Brittonic fortress at Dumbarton Rock in 870, initiated by the Viking leaders Amlaíb, King of Dublin, and Ímar. Dumbarton was capital of the Kingdom of Alt Clut, the only surviving Brittonic kingdom outside of Wales. It represented a valuable target for the Viking invaders, who were likely motivated by strategic considerations, as well as loot. The attackers may have wished to remove Alt Clut as a maritime power, and the location and defensiveness of Dumbarton itself was of major value.
The siege lasted four-months, a length of time unprecedented in the history of Viking warfare in the British Isles, and ended when the defenders ran out of water. After the siege numerous prisoners were taken and sold into slavery in Dublin. Following this defeat, the power centre of Alt Clut moved to the vicinity of Govan, and it became known as the Kingdom of Strathclyde. The loss of Dumbarton caused the kingdom to increasingly fall under the influence of the Scottish Kingdom of Alba.
Following the Anglo-Saxon invasion of Britain, the Kingdom of Alt Clut was the only remaining Brittonic kingdom outside of Wales. At the time of the siege it was ruled by Arthgal ap Dyfnwal.
For most of the 9th century, Alt Clut had escaped the worst of the Viking invasions of Scotland. By 870, the settlement on Dumbarton Rock was the centre of a small but wealthy kingdom. The site was strategically important, commanding the confluence of the rivers Clyde and Leven. Conquering Dumbarton would make it possible for the Vikings to sail upriver into the central lowlands of Scotland. Dumbarton Rock was an extremely strong defensive position and had previously survived several sieges, including a co-ordinated assault by Angles and Picts in 756.
Following his successful invasion of England, including the conquest of York in 866, Ímar joined forces with Amlaíb, the Scandinavian King of Dublin, to target this prosperous town. Aside from loot, possible objectives might have included neutralising the Britons as a maritime power. No other campaign by Ímar and Amlaíb involved such a concentrated assault in one place, providing evidence of Alt Clut's continuing power at the time.
In 870 Amlaíb and Ímar gathered their combined forces and launched their attack on Dumbarton. Unable to take the fortress, they besieged the rock for a period of four months, a length of time highly unusual for the period, and unprecedented in the history of Viking warfare in the British Isles. The defenders survived four months of the siege before the well ran dry, forcing them to capitulate.
The ground they fought on
The site of Siege of Dumbarton lies on Paleozoic sedimentary rocks, bedrock that formed in the Devonian. The rock here is sedimentary rocks.
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- Siege of Dumbarton · Wikidata
- Siege_of_Dumbarton · Wikipedia