Irish History From The Annals
The Irish victory at the battle of Tara in 980 AD opened the way for the capture of Viking Dublin and the freeing of the Irish slaves.
The Viking city of Dublin had by the tenth century grown into a wealthy and powerful trading centre and part of its wealth was based on the export and sale of Irish slaves. These slaves were captured in periodic raiding expeditions. But by the end of the tenth century the power of the Vikings was beginning to wane as the Irish Kings became more powerful. In 980 Mael Sechnaill mac Domnaill the Ui Neill King of Mide (Meath) defeated the Vikings of Dublin and their allies from the Hebrides and the Isle of Man in a decisive battle at or near Tara in Co. Meath. The battle of Tara lead to the abdication of the King of Dublin, Amhlaibh mac Sitric, and his retirement to the monastery of Iona. The battle lead to the accession of Mael Sechnaill to the High Kingship of Ireland; and the defeat of the Viking army opened the way to Dublin.
Annals of the Four Masters
record that the following year Mael Sechnaill advanced on Dublin. Following a siege of three days he captured the city. Mael Sechnaill then released over 2,000 hostages held by the Vikings and forced the Vikings to renounce the tribute they had exacted from the Ui Neill. Then he issued a proclamation freeing all the Irish slaves in the territory of the Vikings. The freeing of the slaves and curtailment of further slaving would have had an impact on the wealth and power of the Dublin Vikings and make them less of a threat in the future. No doubt the freeing of the slaves could be seen as a calculated political move to make Mael Sechnaill popular throughout Ireland. But it can also be seen as a display of humanity from a medieval warrior King. Mael Sechnaill was to remain High King for another 22 years when he was succeeded by Brian Boruma who would also fight a famous battle against the Vikings of Dublin at Clonard in 1014.
A great army was led by Maelseachlainn, son of Domhnall, King of Ireland, and by Eochaidh, son of Ardgar, King of Ulidia, against the foreigners of Ath-cliath; and they laid siege to them for three days and three nights, and carried thence the hostages of Ireland, and among the rest Domhnall Claen, King of Leinster, and all the hostages of the Ui-Neill. Two thousand was the number of the hostages, besides jewels and goods, and the freedom of the Ui- Neill, from the Simian to the sea, from tribute and exaction. It was then Maelseachlainn himself issued the famous proclamation, in which he said:— "Every one of the Gaeidhil who is in the territory of the foreigners, in servitude and bondage, let him go to his own territory in peace and happiness." This captivity was the Babylonian captivity of Ireland, until they were released by Maelseachlainn; it was indeed next to the captivity of hell.