On 6 May 1527, the eternal city was invaded by mercenaries of Emperor Charles V. Today we also speak of it as the "Sacco di Roma", the Sack of Rome. In this attack, the Swiss stood no chance, even though they desperately put up resistance. From the total of 189 Swiss Guards, only 42 survived. However, they succeeded at the last minute in getting Pope Clement VII to safety through the secret passage ("Passetto") to Castel Sant'Angelo.
Even today, to commemorate this historic event, the annual swearing-in of new recruits is traditionally held on 6 May. Besides the newly sworn in guards and their relatives, key representatives of the government and the church take part in this ceremony.