On the 12th of January, nine days after the battle, Don Juan surrendered the town, and agreed to give up at the same time Dunboy, Baltimore, and Castlehaven. He had lost 1,000 men out of his 3,000 during a ten weeks' siege, and was heartily sick of Irish warfare. On his return to Spain he was degraded from his rank, for his too great intimacy with Carew, and confined a prisoner in his own house. He is said to have died of a broken heart occasioned by these indignities.
O'Donnell sailed from Castlehaven in a Spanish ship, on the 6th of January, three clays after the battle, and arrived at Corunna on the 14th. He was received with all the honours due to a crown prince by the Conde de Caracena, Governor of Galicia. Among other objects, he visited the remains of the tower of Betanzos, from which, according to Bardic legends, the sons of Milesius had sailed to seek for the Isle of Destiny among the waves of the west. On the 27th he set out for the Court, accompanied as far as Santa Lucia by the governor, who presented him with 1,000 ducats towards his expenses. At Compostella the Archbishop offered him his own palace, which O'Donnell respectfully declined: he afterwards celebrated a Solemn High Mass for the Irish chief's intention, entertained him magnificently at dinner, and presented him, as the governor had done, with 1,000 ducats. At Zamora he received from Philip III. a most cordial reception, and was assured that in a very short time a more powerful armament than Don Juan's should sail with him from Corunna. He returned to that port, from which he could every day look out across the western waves that lay between him and home, and where he could be kept constantly informed of what was passing in Ireland. Spring was over and gone, and summer, too, had passed away, but still the exigencies of Spanish policy delayed the promised expedition. At length O'Donnell set out on a second visit to the Spanish Court, then at Valladolid, but he reached no further than Simancas, when, fevered in mind and body, he expired on the 10th of September, 1602, in the 29th year of his age. He was attended in his last moments by two Franciscan Fathers who accompanied him, Florence, afterwards Archbishop of Tuam, and Maurice Donlevy, of his own Abbey of Donegal. His body was interred with regal honours in the Cathedral of Valladolid, where a monument was erected to his memory by the King of Spain.