This was agreed in a meeting at Clonmacnoise in 900, and Cathal is found frequently fighting alongside and on behalf of Flann.
In 907, the forces of Munster campaigned against the Connachta as far as Mag nAí (in central modern County Roscommon) and the Ui Neill and took the hostages of Connacht.
[4] In 913, Niall Glúndub (died 919) of the Cenél nEógain of the northern Ui Neill began to make his bid to be recognized as heir to the high Kingship.
Whether this was the usual attempt of a new high king to impose his authority on Connacht or directed against the intense Viking activity on the Shannon at this time is not mentioned.
The King of Aidne, Mael son of Duí had been killed by Vikings that year[6] The death of Cathal's heir is mentioned in the annals in 923.