He was styled Viscount Thurles from 1634 until 1642 and from then onwards Earl of Ossory. However, he became known in history as 'Gallant Ossory'. He was educated in France from 1648 until 1652. Oliver Cromwell imprisoned him in The Tower from March till October 1655. From 1657 until 1660 he resided in Holland there, in 1659, he married Emilia van Nassau and they produced five children.
He was a Tory M.P. for Bristol from 1661 until 1666 as well as M.P. for the University of Dublin in 1661 and 1662. At Charles II's coronation on 23 April 1661 he was one of the train bearers.
On behalf of his father he was Deputy Governor of Ireland from 21 May 1664 until 3 September 1665 and again from 10 April 1668 to 3 May 1669. On 16 September 1665 he was appointed Lieutenant-General of the forces in Ireland which he remained until he died.
As a volunteer on the 'Royal Charles' he distinguished himself in the Four Days' Fight with the Dutch in June 1666. On 14 September 1666 he was summoned to the House of Lords as Lord Butler of Moore Park. In October 1670 he was sent to Holland to accompany the Prince of Orange
to England.
He was Captain of the 'Resolution' and second in command in the attack on the Dutch Smyrna Fleet on 12 March 1672. He was then Captain of the 'Victory' at Solebay on 28 May 1672 when he was slightly wounded. In 1672 he also became a Knight of The Garter. In November 1672 he was sent to France to condole the French king on the death of the Duke of Anjou. In May 1673 he was appointed Rear-Admiral of the Blue and Captain of the 'St.Michael' when he served with distinction
against the Dutch Admiral Michiel de Ruyter in the battles of Schooneveld, 28 May 1673, and Texel, 11 August 1673.
He became Vice-Admiral of the Red in August 1673 and Commander-in-Chief at the Nore in September 1673. From November 1676 until his death he was Chamberlain to the Queen. For the siege of Charleroi, July 1677, he joined the Prince of Orange. In July 1680 he was nominated Governor of Tangier but, after 4 days' illness, died 30 July 1680 at Arlington House, London, aged forty-six.

Source: Leo van de Pas