Conn Bacach O'Neill, Earl of Tyrone, was determined to bring the O'Donnells under his rule and made a great gathering, determined to march into Tyrconnell. Forces arrived from Munster and Connacht, together with English contingents, and brought into O'Neill's army itself were the Scoto-Irish MacDonnells of Antrim, Bissetts, MacSheehys and others. The forces laid siege to and took Ballyshannon Castle, and later devastated a large part of Tyrconnell.