Tyrone's loyalty reached infatuation, persisted in hoping against hope, attributing his failure to Russell's bad faith in detaining Philip's letter to Tyrone. At the end of August two ‘barks of adviso’ were announced to have arrived at Killybegs, and O'Donnell, Tyrone, and O'Rourke at once posted thither. Letters signed by them addressed to the king of Spain, the Infante, and Don Juan d'Aquila, were betrayed to the government by Tyrone's secretary, Nott, after which further dissimulation was impossible.
Towards the end of the year Donough O'Conor Sligo was restored; and O'Donnell, after vainly trying to win him over by bribes and threats, again invaded Connaught in January 1597. Accompanied by MacWilliam (Theobald Burke), he plundered O'Conor Sligo's adherents, fired Athenry, and harried the country to the very gates of Galway, returning to Tyrconnel laden with an immense quantity of booty. With the exception of Thomond the whole province lay at his mercy, when Sir Conyers Clifford [q. v.] arrived in February to vindicate the authority of the crown. Owing to the smallness of the force at his disposal, Clifford was for some time compelled to act mainly on the defensive; but, with his assistance, O'Conor Sligo succeeded in March in establishing himself in Sligo, and in forcing O'Donnell to retreat across the Erne. In May Theobald Burke was expelled from Mayo; and, stimulated by his success, Clifford in July made an attempt to capture Ballyshannon. He succeeded in crossing the Erne, but was repulsed with heavy loss by O'Donnell in the neighbourhood of Ballyshannon. Relieved from all apprehension on the side of Connaught, O'Donnell marched to assist Tyrone in an attack on the new fort on the Blackwater, but subsequently consented to a cessation of hostilities. On the renewal of the war in the following summer he again went to Tyrone's assistance, and took part in the memorable defeat of Sir Henry Bagnal at the Yellow Ford on 14 Aug. But hearing that Clifford had designs on Ballymote, he marched thither, and, having forced MacDonough to surrender it, he fixed his residence there and plundered Connaught and Thomond at his pleasure. But his main object was to reduce O'Conor Sligo, and accordingly, in the summer of 1599, he besieged him in Collooney Castle. Essex sent Clifford to O'Conor's assistance; but O'Donnell, who was fully informed of his movements, despatched a strong force under O'Rourke against him. While crossing the Curlews Clifford was attacked by O'Rourke and utterly defeated. O'Conor Sligo thereupon submitted, and his example was followed by Theobald-na-Long (son of Richard-of-the-Iron Burke) [see Malby, Sir Nicholas].
The death of Hugh Maguire early in 1600, and the question of the appointment of his successor, led to a serious difference of opinion between O'Donnell and Tyrone, the former supporting the claims of Maguire's brother Cuconnacht, the latter those of his son Conor. In the end O'Donnell carried the day, but not without giving great offence to Tyrone. In May Sir Henry Docwra [q. v.] arrived in Lough Foyle, and succeeded in entrenching himself at Derry. O'Donnell, who was then at Ballymote, sent his cousin Niall Garv to dislodge him, while he himself went on a marauding expedition into Thomond. The summer passed away, and Docwra continuing to defy Niall Garv, O'Donnell marched against him in September; but failing to draw him from his entrenchments, he returned to Ballymote, and was already preparing for a fresh campaign into Thomond when he was hastily recalled by the news that Niall Garv had gone over to Docwra and that Lifford had fallen into his hands. After several determined but unsuccessful attempts to recover the place, O'Donnell retired across the Finn into winter quarters. His spirits were somewhat revived by the arrival shortly afterwards from Spain of Matthew de Oviedo with a considerable supply of money and arms, which he shared equally with Tyrone. But his policy of aggression was beginning to bear its natural fruit, and old Ulick Burke, earl of Clanricarde, having died in May 1601, his successor, Richard, prepared to attack O'Donnell in his own country. Ever prone to strike the first blow, O'Donnell moved towards Ballymote. His absence afforded Niall Garv an opportunity, which he did not neglect, to capture Donegal and to fortify the abbey. Recalled by this fresh disaster, O'Donnell was still engaged in besieging the place when the news of the arrival of the Spaniards in Kinsale Harbour reached him.
Immediately raising the siege and collecting all his followers together at Ballymote, he moved rapidly southwards, plundering his enemies by the way and successfully evading Sir George Carew, who had been sent to intercept him. Fixing his camp at Bandon, he was joined there at the end of November by Tyrone, when the two chiefs moved to Belgoly, intercepting all communications between the English investing Kinsale and the surrounding country. Both seem to have been agreed as to the policy of starving out the English; but the impatience, or perhaps the privations, of the Spanish commander urging
