[1] French troops had already occupied Rome in February 1808, followed by the Marches,[2] and in April of that year a decree by Napoleon announced the annexation of the Church States, although without affecting the pope's power in the capital.

In other times, many Sovereign Pontiffs, whom holiness and learning rendered illustrious, were obliged, because the cause of the Church required it, to resort to similar extreme measures against rebellious kings and princes who had been guilty of only one or two of the crimes which the canons condemn with anathema; shall We then fear to follow their example after witnessing so many evil deeds, and sacrileges so heinous and so universally known?

After initial hesitation General Sextius Miollis, commander of the French garrison in the city, allowed the operation to proceed, as Colonel Étienne Radet argued that Rome could no longer be governed unless a display of strength was made.

In the early hours of 6 July, less than a month after the issuing of the Quum memoranda, a French unit led by Radet stormed the Quirinal Palace and arrested Pius, who was then taken to a carriage and departed the city.

After short stays in Genoa and Grenoble, a large house in Savona was chosen as a suitable place for Pius to settle in his exile, while still being allowed to conduct ceremonies and receive visits from the local population.