The Irish rebel James Fitzmaurice Fitzgerald, called Fitzmaurice, had fled in 1575 to the European continent, despite his pardon.

He had been warmly received the following year at Rome, where Father William Allen, close to Gerald Fitzgerald, 15th Earl of Desmond, was also present, having presented to the pope a plot for the invasion of England through Liverpool, with five thousand musketeers under Thomas Stukley's command.

The Geraldine connection had been made, and in 1578 Stukley is provided by the pope with infantry and sets out with two thousand men, including musketeers (or maybe swordsmen); the force has been raised by enlisting Appennine highwaymen and robbers in return for pardons and fifty-day indulgences, the latter to be gained by contemplation of crucifixes supplied to Stukley—although there are also professional officers, including the commander, Hercules of Pisano, and also Giuseppi, who will go on on to command the Smerwick garrison at the beginning of the Second Desmond Rebellion.

In sum, Stukley's ranks rise to four thousand.

Stukley sails for Ireland from Civitavecchia in March 1578.

Clement XIII's pontificate will be repeatedly disturbed by disputes respecting the pressures to suppress the Jesuits coming from the progressive Enlightenment circles of the philosophes in France.

Clement XIII places the Encyclopédie of D'Alembert and Diderot on the Index Librorum Prohibitorum, but this index is not as effective as it had been in the previous century.

More unexpected resistance comes from the less progressive courts of Spain, the Two Sicilies, and Portugal.

The reforming minister of Joseph I of Portugal, the future Marquis of Pombal, expels the Jesuits from Portugal in 1759 and transports them all to Civitavecchia, as a "gift for the Pope."