Excerpts from Books and Wikipedia
"The capture and sacking of Rome in 1527 by a mutinous imperial army, with Pope Clement VII fleeing for his life down a secret Vatican passage to take refuge in the Castel Sant'Angelo, was an event that shocked Europe and shamed Emperor Charles V. . . . The troops did not withdraw until June 6, when Pope Clement agreed to pay a ransom of 400,000 ducats. Although the sack was condemned by Charles V and beyond his control, few lamented the predicament of the weak Clement VII, the last Renaissance prince-pope." [Furtado: 1001 Days]