In presenting so comprehensive an ultimatum to Essex, O'Neil was emboldened by the latest intelligence received from Spain. Philip II., the life-long friend of the Catholics, had, indeed, died the previous September, but one of the first acts of his successor, Philip III., was to send envoys into Ireland, assuring its chiefs that he would continue to them the friendship and alliance of his father. Shortly before the conference at Anaghclart, a third Armada, under the Adelantado of Castile, was awaiting orders in the port of Corunna, and England, for the third time in ten years, was placed in a posture of defence. The Spaniards sailed, but soon divided into two squadrons, one of which passed down the British Channel unobserved, and anchored in the waters of the Sluys, while the other sailed for the Canaries to intercept the Hollanders. At the same time, however, most positive assurances were renewed that an auxiliary force might shortly be expected to land in Ireland in aid of the Catholics. The non-arrival of this force during the fortunate campaign of 1599 was not much felt by the Catholics; and was satisfactorily explained by Philip's envoys—but the mere fact of the existence of the Spanish alliance gave additional confidence and influence to the confederates. That fact was placed beyond all question by the arrival of two Spanish ships laden with stores for O'Neil, immediately after the interview with Essex. In the summer or autumn ensuing, Mathew of Oviedo, a Spaniard, consecrated at Rome, Archbishop of Dublin, brought over 22,000 crowns towards the pay of the Irish troops, and a year afterwards, Don Martin de la Cerda was sent to reside as envoy with Tyrone.
The year 1600 was employed by Hugh O'Neil, after the manner of his ancestors, who were candidates for the Kingship of Tara, in a visitation of the Provinces. Having first planted strong garrisons on the southern passes leading into Ulster, he marched at the head of 3,000 men into West-Meath, where he obliged Lord Delvin and Sir Theobald Dillon to join the Confederation. From Meath he marched to Ely, whose chief he punished for a late act of treachery to some Ulster soldiers invited to his assistance. From Ely he turned aside to venerate the relic of the Holy Cross, at Thurles, and being there he granted his protection to the great Monastery built by Donald More O'Brien. At Cashel he was joined by the Geraldine, whom he caused to be recognized as Earl of Desmond. Desmond and his supporters accompanied him through Limerick into Cork, quartering their retainers on the lands of their enemies, but sparing their friends; the Earl of Ormond with a corps of observation moving on a parallel line of march, but carefully avoiding a collision. In the beginning of March the Catholic army halted at Inniscarra, upon the river Lee, about five miles west of Cork. Here O'Neil remained three weeks in camp consolidating the Catholic party in South Munster. During that time he was visited by the chiefs of the ancient Eugenian clans—O'Donohoe, O'Donovan, and O'Mahoney: thither also came two of the most remarkable men of the southern Province, Florence McCarthy, Lord of Carberry, and Donald O'Sullivan, Lord of Bearehaven. McCarthy "like Saul, higher by the head and shoulders than any of his house," had brain in proportion to his brawn; O'Sullivan, as was afterwards shown, was possessed of military virtues of a high order. Florence was inaugurated with O'Neil's sanction as McCarthy More, and although the rival house of Muskerry fiercely resisted his claim to superiority at first, a wiser choice could not have been made had the times tended to confirm it.