Máel Sechnaill
During the reign of Máel Sechnaill mac Máele Ruanaid, who succeeded Áed's father as High King, the balance of power between north and south which had ensured the alternating succession appeared to be tipping in favour of the southern Clann Cholmáin kindred. The weakness of the Kings of Munster following the death of the powerful Feidlimid mac Crimthainn in 847 led to repeated attacks on Munster by Máel Sechnaill in the 850s and a submission by the kings of Munster in 858. In 859, Osraige was made subject to the Uí Néill, and this led to open warfare between Máel Sechnaill and Áed.