23 March‭ ‬1535: Sir William Skeffington captured Maynooth Castle [model above]* on this day. Skeffington had been sent over from England by Henry VIII to impose Royal rule upon the Irish and Anglo-Irish Lords. He was faced with a military revolt by Lord Thomas Fitzgerald. This young man feared for his father, the great Garrett Oge Fitzgerald, who was held captive in the Tower of London. Lord Thomas or ‘Silken Thomas’ was a rash and impetuous youth who badly misjudged his own power and abilities. But the power of his family’s name and the desire of the Catholics of Ireland to pre-empt the imposition of the English Reformation upon Ireland led to a flush of initial success that rapidly petered out at the end of 1534.

‭Sir William Skeffington remained inactive during the whole winter. But in March 1535 he laid siege to the castle of Maynooth, the strongest of Fitzgerald's fortresses, which was defended by 100 men. After a siege of nine days, during which the castle was battered by artillery, then for the first time used in Ireland, he took it by storm, except the great keep; and the garrison who defended this, now reduced to thirty-seven men, seeing the case hopeless, surrendered, doubtless expecting mercy.
A Concise History of Ireland by P.‭ W. Joyce

The siege began on the‭ 14 March and lasted nine days. Eventually the outer defenses were stormed under a hail of artillery, marking the first time a castle in Ireland was taken through the use of such a weapon. Only the great keep remained untaken and the survivors struck terms that their lives would be spared if they would but come out and lay down their weapons.

Skeffington wrote to King Henry:
Their lives were preserved by appointment,‭ until they should be presented to me, your deputy, and then to be ordered, as I and your council thought good. We thought it expedient to put them to execution as an example to others (Carew Papers). Local tradition holds that they were hanged from the central arch of the castle.
The Neighbourhood of Dublin
By Weston St.‭ ‬John Joyce

However the Lord Deputy’s ruthlessness backfired on his successors,‭ as his actions only made future defenders more wary of such capitulations and ‘the Pardon of Maynooth’ became a byword for treachery amongst the Irish.

* https://neverfeltbetter.wordpress.com/2012/07/17/irelands-wars-the-siege-of-maynooth/