The Earl of Thomond was proclaimed rebel in 1570, and fled to sea; the Earl of Ormond meantime garrisoned Bunratty with his own men, but in 1585 the castle was confirmed to the Earl of Thomond.
The “Great Earl” of Thomond restored it in 1617.
Some authorities say Lord Forbes seized the castle in 1642 in a buccaneering expedition.
When the rebellion broke out in 1641 the Earl of Thomond of the time found himself in a difficult position, for by religion he might have been supposed to side with the Government, while at the same time he was closely related to many of the prominent Confederates, being uncle to Lord Muskerry who commanded their troops in the south. He, therefore, remained quietly at Bunratty taking neither side, but he was too powerful to be allowed to presevere in neutrality.
The Supreme Council of the Confederates entrusted the seizure of both the castle and Earl to his relatives, the O’Briens, but in the meantime the Earl of Ormond had entered into a treaty with the Earl of Thomond whereby the latter was to surrender the castle of Bunratty to a governor they mutually agreed upon.
The choice fell upon Colonel Adams, “a stout officer,” who, with upwards of six hundred men, took possession of the stronghold in 1645. The governor was a Scotchman whose family name was Adam, but upon settling in Ireland he seems to have been called Adams, and sometimes MacAdam. He was married to the Hon. Catherine Magennis, granddaughter of Hugh, Earl of Tyrone, therefore his wife was first cousin to Owen Roe O’Neill, which, no doubt, guided his selection as commander of Bunratty garrison.
Before the castle was surrendered the Earl of Thomond built all his plate and money into the walls to the amount of £2,000, and had the place plastered and rough cast. Some of the servants betrayed the fact to the soldiers, and they seized the Earl and threatened to kill him unless he showed them the treasure, whereupon they took it before his face. He afterwards tried to recover it as a debt from the Government in vain.
The castle was provisioned at the cost of £1,200 by John Davies.
The Earl of Thomond left his fortress in the hands of the soldiers and sailed for England. Colonel Adams at once set to work to put the place in a state of defence by raising earthworks and fortifying outlying positions, as well as mounting cannon in the garden, his was much helped in his operations by the marshy character of the surrounding country.
The Confederates sent an army to besiege the castle, which encamped in the park. They were shortly afterwards joined by Lord Muskerry, who seems to have been only half-hearted in attacking his uncle’s property, and it required the persuasion and presence of the Nuncio to push the siege to a victorious issue.