The first mention of Cellach in the annals involves the Battle of Áth Orc (in County Offaly) in 770.
[2] Leinster had suffered a major defeat at the hands of the high king Áed Allán of the Cenél nEógain at the Battle of Áth Senaig (Ballyshannon, Co. Kildare) in 738.
In 770, however, the new high king Donnchad Midi (died 797) of the Clann Cholmáin asserted his suzerainty over Leinster.
Donnchad remained seven days in the vicinity of the ancient hill fort of Ráith Ailenn (in Co.Kildare) and ravaged the country with fire until the men of Leinster submitted to him.
[3] That same year of 770 the two septs of the Síl nÁedo Sláine branch of the southern Uí Néill made border attacks on Leinster territory.