Congalach and Amlaíb fight against Ruaidrí ua Canannáin, a rival for the High Kingship who belongs to the Cenél Conaill, based in modern County Donegal.

The two defeat part of Ruaidrí's army in 945 in Conaille Muirtheimne (modern County Louth).

Ruaidrí routs Congalach and Amlaíb at Slane in 947.

Losses among the Dublin men are heavy, with many drowning while fleeing the battle.

The defeat at Slane appears to have lost Amlaíb his kingship, as the annals record that Blácaire not Amlaíb is the leader of the Dublin forces in the following year.

Blácaire is killed in 948 by Congalach, and is succeeded by Amlaíb's brother Gofraid.