'We have felt great pain and shame for the offence given to the Holy See, indeed we would have preferred not to win than to be left with such a victory.'
During the first phase of the Habsburg-Valois wars, Charles V permitted his army garrisoned in Milan to be used against Papal troops who were engaged against one of his Italian allies. However, under the Duke of Bourbon, they marched on Rome. Bourbon died during the assault on the city, but it was stormed on the 6th May 1527. The leaderless and underpaid troops embarked on a week long orgy of rape, pillage and destruction. The Pope fled the city but was soon captured by the Habsburg troops.
Christian Europe was horrified, and Charles was dismayed. Rather than taking blame, he mounted a propaganda campaign in Western Europe to convince people that the real blame lay with his enemies - specifically, Francis I of France and the Pope.
Late in 1527 Charles released the chastened Pope Clement, who was henceforth much more reluctant to act against him.