(1600–50), Catholic bishop of Clogher, a representative of the militant Counter-Reformation. A product of the Irish colleges in Flanders, he recruited mercenaries for continental service under Owen Roe O'Neill. MacMahon was a delegate to the Synod of Kells (March 1642), which declared the rising of 1641 ‘a just and pious undertaking’, and subsequently member of the confederate supreme council. Supporters of the Ormond peace tried to appoint him a foreign ambassador but he refused to go and later broke with them over the Inchiquin truce. The compromise choice to succeed O'Neill as general of Ulster, he was executed following defeat at Scarrifhollis (see confederate war).
From The Oxford Companion to Irish History in Oxford Reference.
Subjects: European History.