Although during the early sixteenth century the family had rebelled against the Crown on several occasions, Ulick's father had been a strong supporter of Queen Elizabeth I.

After the war, he married the widow of the 2nd Earl of Essex, a recent commander in Ireland, who was the daughter of the English Secretary of State and spymaster Sir Francis Walsingham.

[2] He was a staunch opponent of the policies of the Lord Deputy of Ireland, Thomas Wentworth, 1st Earl of Strafford, who had attempted to seize much of the great Burke inheritance in Connacht for the Crown; there was also personal ill-feeling between the two men since the dispute was thought by many to have hastened the death of Ulick's elderly father.

He commanded the forces of this alliance during the Cromwellian conquest of Ireland, after Lord Ormonde fled the country, and soldiers of his Connaught army helped to win a minor victory at the Battle of Tecroghan.

Like Ormonde, Clanricarde was distrusted by most Catholics in Ireland (he was widely considered to be a friend of the notorious Charles Coote) and thus was thus not capable of halting the Parliamentarian conquest of the country.