This renunciation of allegiance was a declaration of open war. The chapter thus opened in the memoirs of the Leinster Geraldines closed at Tyburn on the 3rd of February, 1537. Within these three years, the policy of annexation was hastened by several events - but by none more than this unconcerted, unprepared, reckless revolt. The advice of the imprisoned Earl to his son had been "to play the gentlest part," but youth and rash counsels overcame the suggestions of age and experience. One great excess stained the cause of "Silken Thomas," while it was but six weeks old. Towards the end of July, Archbishop Allan, his father's deadly enemy, left his retreat in the Castle, and put to sea by night, hoping to escape into England. The vessel, whether by design or accident, ran ashore at Clontarf, and the neighbourhood being overrun by the insurgents, the Archbishop concealed himself at Artane. Here he was discovered, dragged from his bed, and murdered, if not in the actual presence, under the same roof with Lord Thomas. King Henry's Bishops hurled against the assassins the greater excommunication, with all its penalties; a terrific malediction, which was, perhaps, more than counterbalanced by the Papal Bull issued against Henry and Anne Boleyn on the last day of August - the knowledge of which must have reached Ireland before the end of the year. This Bull cited Henry to appear within ninety days in person, or by attorney, at Rome, to answer for his offences against the Apostolic See; failing which, he was declared excommunicated, his subjects were absolved from their allegiance, and commanded to take up arms against their former sovereign. The ninety days expired with the month of November, 1534.
Lord Thomas, as he acted without consultation with others, so he was followed but by few persons of influence. His brothers-in-law, the chiefs of Ely and Offally, O'Moore of Leix, two of his five uncles, his relatives, the Delahides, mustered their adherents, and rallied to his standard. He held the castles of Carlow, Maynooth, Athy, and other strongholds in Kildare. He beseiged Dublin, and came to a composition with the citizens, by which they agreed to allow him free ingress to assail the Castle, into which his enemies had withdrawn. He despatched agents to the Emperor, Charles V., and the Pope, but before those agents could well have returned - March, 1535 - Maynooth had been assaulted and taken by Sir William Skeffington - and the bands collected by the young lord had melted away. Lord Leonard Gray, his maternal uncle, assumed the command for the King of England, instead of Skeffington, disabled by sickness, and the abortive insurrection was extinguished in one campaign. Towards the end of August, 1535, the unfortunate Lord Thomas surrendered on the guarantee of Lord Leonard and Lord Butler; in the following year his five uncles - three of whom had never joined in the rising - were treacherously seized at a banquet given to them by Gray, and were all, with their nephew, executed at Tyburn, on the 3rd of February, 1537. The imprisoned Earl having died in the Tower on the 12th of December, 1534, the sole survivor of this historic house was now a child of twelve years of age, whose life was sought with an avidity equal to Herod's, but who was protected with a fidelity which defeated every attempt to capture him. Alternately the guest of his aunts married to the chiefs of Offally and Donegal, the sympathy everywhere felt for him led to a confederacy between the Northern and Southern Chiefs, which had long been wanting. A loose league was formed, including the O'Neils of both branches, O'Donnell, O'Brien, the Earl of Desmond, and the chiefs of Moylurg and Breffni. The lad, the object of so much natural and chivalrous affection, was harboured for a time in Munster, thence transported through Connaught into Donegal, and finally, after four years, in which he engaged more of the minds of statesmen than any other individual under the rank of royalty, was safely landed in France. We shall meet him again in another reign, under more fortunate auspices.
Lord Leonard Gray continued in office as Deputy for nearly five years (1535-40). This interval was marked by several successes against detached clans and the parties to the Geraldine league, whom he was careful to attack only in succession. In his second campaign, O'Brien's bridge was carried and demolished, one O'Brien was set up against another, and one O'Conor against another; the next year the Castle of Dungannon was taken from O'Neil, and Dundrum from Magennis. In 1539, he defeated O'Neil and O'Donnell, at Bolahoe, on the borders of Farney, in Monaghan, with a loss of 400 men, and the spoils they had taken from the English of Navan and Ardee. The Mayors of Dublin and Drogheda were knighted on the field for the valour they had shown at the head of their train-bands. The same year, he made a successful incursion into the territory of the Earl of Desmond, receiving the homage of many of the inferior lords, and exonerating them from the exactions of those haughty Palatines. Recalled to England in 1540, he, too, in turn, fell a victim to the sanguinary spirit of King Henry, and perished on the scaffold.