His personal authority, with duties similar to a Tacksman to a Scottish clan chief, covered "that part of Tirconnell from the mountain westwards, i.e. from Barnesmore to the river Drowes (i.e. Tirhugh), and also all the inhabitants of Boylagh and Tir Boghaine (i.e.
[4] His father's primary domain concentrated on Kilmacrenan and Mongavlin, and his cousin Niall Garbh O'Donnell, with similar duties, held sway over the Clan's traditional stronghold of Lifford and eastwards of there.
[5] The Four Masters described him as "a mighty champion and great in battle, and it was never heard that at any time he had turned his back on his enemies" and O'Donovan says he was known "to lead his father's forces".
Donal received the allegiance of O'Boyle and MacSweeney Banagh, as well as of the English Crown, who felt he had a stronger claim to the Lordship, by primogeniture.
In 1589 a force of Irish Army troops were sent into the area under Captain John Connill who assisted Sir Donal against his rivals.