the Unfilial or Áed the Undutiful, the only byname used in early sources. It is generally supposed that this refers to his conflict with his father-in-law Donnchad Midi, although the term mac ingor, a term from early Irish law, usually refers to the undutiful son who does not support his biological father. Whatever the origin of the name may have been, it is plainly not flattering. In 794 Áed is recorded as campaigning against the Mugdorna Maigen at a time when Donnchad was involved in war with Munster. The lands of Mugdorna Maigen lay around the upper reaches of the river Fane, with the chief church at Donaghmoyne, County Monaghan. Although reckoned one of the nine tribes of the Airgíalla, the Mugdorna were clients of the southern Síl nÁedo Sláine branch of the Uí Néill rather than of Áed's Cenél nEógain dynasty like most of the Airgíalla. King of Tara Although Donnchad's authority waned in the last decade of his life, he remained the dominant figure until his death on 6 February 797. Following Donnchad's death, Áed moved to ensure that he would be recognised as king of Tara. He defeated two of Donnchad's brothers, Diarmait and Fínsnechta, along with another Fínsnechta, a son of Fallomon mac Con Congalt of Clann Cholmáin Bicc, at Druim Ríg (modern Drumree) in south Brega. A poem in the Annals of Ulster portrays this as vengeance for the death of Áed's uncle Áed Allán at the hands of Donnchad's father Domnall Midi at the battle of Seredmag in 743. Some time later in 797 Áed devastated Mide and the Annals of Ulster take this to mark the beginning of his reign. In 802 Muiredach, king of Mide, died. He was the last of Donnchad Midi's known brothers. Áed led an army south to Mide where he divided the lands of Clann Cholmáin between two of Donnchad's sons, Ailill and Conchobar. If this was intended to reduce the power of potential rivals, it proved ineffective. Ailill and Conchobar met in battle in 803 at Rath Conaill (near modern Mullingar). Ailill was killed leaving Conchobar as sole king of Mide. In 804 Áed turned his attention towards Leinster and devastated the area twice in one month. That same year Fínsnechta Cethardec (died 808), King of Leinster, submitted to him. However Áed was not satisfied with this and in 805 he made a hosting to Dún Cuair