Born when the Uí Ímair ruled over large areas of the British Isles, by his death the kingdom of Dublin was a minor power in Irish politics.

At the same time, Dublin became a major centre of trade in Atlantic Europe and mastery over the city and its wealth became the supreme prize for ambitious Irish kings.

During the second quarter of the century the frequency and size of raids increased and the first permanent Viking settlements (called longphorts in Ireland) appeared.

[5] Amlaíb's father Sitriuc first appears in the record in 917 when he seized Dublin, a settlement which had probably been under the control of an Irish king since the expulsion of the previous Viking rulers in 902.

According to some late sources, such as the chronicler John of Wallingford, copying a lost northern record, Amlaíb was the son of Sitriuc and Æthelstan's sister, perhaps called Osgifu or Eadgyth.

According to William of Malmesbury, Amlaíb fled to Ireland while his uncle Gofraid made a second unsuccessful attempt to gain control of York.

[12] William of Malmesbury wrote that Amlaíb was present at Brunanburh and spied out the English camp the night before the battle disguised as a skald.

The dating of events in the period between the death of Æthelstan and the expulsion of Amlaíb and Ragnall is uncertain as the various versions of the Anglo-Saxon Chronicle are in conflict.

It appears that after Æthelstan's death, not only did Edmund lose control of Northumbria, but that the Five Burghs of the Mercian Danelaw also pledged themselves to Amlaíb mac Gofrith.

[23] Æthelweard's history reports that Amlaíb was deposed by a coup led by Wulfstan, Archbishop of York, and an unnamed Mercian ealdorman.

[26] Congalach and Amlaíb fought against Ruaidrí ua Canannáin, a rival for the High Kingship who belonged to the Cenél Conaill, based in modern County Donegal.

In 945 the two defeated part of Ruaidrí's army in Conaille Muirtheimne (modern County Louth) and the following year Amlaíb raided Kilcullen in the province of Leinster.

The Anglo-Saxon Chronicle records that Eadred "reduced all the land of Northumbria to his control; and the Scots granted him oaths that they would do all that he wanted".

[29] The Northumbrian submission to Eadred led to a meeting with the notables of York led by Archbishop Wulfstan in 947, but the following year King Erik was back ruling Northumbria and Eadred laid waste to the southern parts of the kingdom— Ripon is mentioned as a particular target—to force the Northumbrians to expel Erik, which they did.

[32] That year Máel Coluim mac Domnaill, the king of Alba, raided Northumbria as far south as the River Tees, capturing many slaves and much loot.

[34] Congalach's rival Ruaidrí was also dead, leaving Amlaíb's former ally as undisputed High King and thus a serious threat to Dublin and the south-eastern Irish kingdom of Leinster.

This threat was perhaps what led to Congalach's death in an ambush at Dún Ailinne (modern County Kildare) or at Tech Guigenn in the region of the River Liffey while collecting tribute in Leinster in 956.

[35] The main beneficiary was the brother of Amlaíb's new wife Dúnflaith, Domnall ua Néill, who became the next High King of Ireland.

The marriage linked Amlaíb not only to the northern Uí Néill kindred of Cenél nEógain, but also to the southern Clann Cholmáin as he was now stepfather to Dúnflaith's young son Máel Sechnaill mac Domnaill.

In 960 the Annals of Ulster report that Cammán, son of Amlaíb mac Gofrith, was defeated at an unidentifiable place named Dub.

Another raid south in 964 ended in a heavy defeat for Amlaíb near Inistogue (modern County Kildare) at the hands of the Osraige.

[38] Until the late 960s Domnall ua Néill, Congalach's successor as would-be High King, was occupied with enemies close to home, and in Connacht and Munster, and did not intervene in Leinster or the hinterlands of Dublin.

[40] In 977, in unknown circumstances, Domnall ua Néill's sons Congalach and Muirchertach were killed and Amlaíb is given credit for their deaths by the annals.

He was evidently ransomed or released as he was killed, along with Muiredach mac Riain of Uí Cheinnselaig of south Leinster, fighting against the Dubliners in 978 at Belan (County Kildare).

[41] Following the death of High King Domnall ua Néill, Amlaíb's stepson Máel Sechnaill mac Domnaill claimed the title.

Máel Sechnaill had become king of Mide and head of Clann Cholmáin in 975 and had inaugurated his reign with an attack on his stepfather when he burned "Thor's Wood" outside Dublin.

Amlaíb's son Ragnall (Rögnvaldr) was among the dead in the battle which followed, and although several kings fighting alongside Máel Sechnaill were killed, the result was clearly a crushing blow for Dublin.

Among his wives was Gormflaith, daughter of Murchad mac Finn, King of Leinster, and future wife of Brian Boru.