In February 1534, his father is summoned to London and appoints the 21-year-old FitzGerald, by then Lord Offaly, deputy governor of Ireland in his absence. In June 1534 he hears rumours that his father has been executed in the Tower of London and that the English government intends the same fate for him and his uncles.
FitzGerald summons the council to St. Mary’s Abbey, Dublin, and on June 11, accompanied by 140 armoured gallowglasses with silk fringes on their helmets (from which he gets his nickname), rides to the abbey and publicly renounces his allegiance to his cousin King Henry VIII, Lord of Ireland.
John Alen, Lord Chancellor of Ireland and Archbishop of Dublin, attempts to persuade FitzGerald not to commit himself to such a rash proceeding. But the young lord’s harper, understanding only Irish, and seeing signs of wavering in FitzGerald’s bearing, commences to recite a poem in praise of the deeds of his ancestors, telling him at the same time that he lingered there too long. Roused by this he throws down the sword of state and rushes from the hall, followed by his adherents. The council sends an order for his immediate arrest to the Lord Mayor of Dublin, who, however, has not sufficient force at his disposal.
The Earl of Desmond and many of FitzGerald’s father’s oldest and best friends reason with him, but he is not to be turned from his purpose. As Vice-Deputy, he has under his control most of the Pale‘s fortresses, and large government stores.
Dublin Castle alone holds out for the King of England. Lord Offaly calls the lords of the Pale to the siege of the Castle. Those who refuse to swear fidelity to him are sent as prisoners to his Maynooth Castle. Goods and chattels belonging to the King’s subjects are declared forfeited, and he announces his intention of exiling or putting to death all born in England. He sends messengers to his cousin and friend Lord Butler, son of the Earl of Ormond, offering to divide the kingdom with him if he would join his cause, but Butler refuses. Several children of the citizens of Dublin in different parts of the Pale are seized as hostages for the good behavior of the city.
In July, FitzGerald attacks Dublin Castle, but his army is routed. He is, rightly or wrongly, judged to be responsible for the execution at Artane of Archbishop Alen, who had tried to mediate. This loses him support from the clergy. According to a long-established tradition, the killers, John Teeling and Nicholas Wafer, misunderstand his order, given in Irish, to “take this fellow away” as an order to kill Alen. By this time his father has taken ill and died in London, and he succeeds him as 10th Earl of Kildare, but the Crown never confirms his title. He retreats to his stronghold at Maynooth Castle, but in March 1535 it is taken by an English force under Sir William Skeffington by bribing a guard, while FitzGerald is absent gathering reinforcements to relieve it. The surrendered garrison is put to death, which becomes known as the “Maynooth Pardon.” He has wrongly assumed that his cause would attract overwhelming support, in particular from Catholics opposed to Henry VIII’s English Reformation. But Henry’s new policy also outlaws Lutheranism, and so Henry is not finally excommunicated until 1538.
In July, Lord Leonard Grey arrives from England as Lord Deputy of Ireland. Fitzgerald, seeing his army melting away and his allies submitting one by one, asks for pardon for his offences. He is still a formidable opponent, and Grey, wishing to avoid a prolonged conflict, guarantees his personal safety and persuades him to submit unconditionally to the King’s mercy. According to the Tree Council of Ireland, legend has it that FitzGerald plays a lute under the boughs of the now oldest planted tree in Ireland, the Silken Thomas Yew, the night before he surrenders to King Henry VIII. In October 1535 he is sent as a prisoner to the Tower of London. Despite Grey’s guarantee, he is hanged, drawn, and quartered with his five uncles at Tyburn, London, on February 3, 1537.
The Attainder of the Earl of Kildare Act 1536 is passed to permit his execution and the confiscation of his property. The 1536 Act remains law until it is repealed by the Statute Law Revision (Pre-1922) Act 2005.
FitzGerald’s revolt causes Henry VIII to pay more attention to Irish matters, and is a factor in the creation of the Kingdom of Ireland in 1541. In particular the powers of the lords deputy are curbed, and policies such as surrender and regrant are introduced. To provide for greater security the Royal Irish Army is established as a standing army.