He crushed the exiled party of Filippo Strozzi, who attempted a revolution of the State, exterminated its leaders, and contrived to rid himself of the powerful adherents who had placed him on the throne.

But he remained a subservient though not very willing ally of Spain; and when he expelled Alessandro Vitelli from the fortress that commanded Florence, he admitted a Spaniard, Don Juan de Luna, in his stead.

During the petty wars of 1552-56 which Henri II.

carried on with Charles V.in Italy, Siena attempted to shake off the yoke of a Spanish garrison established there in 1547 under the command of Don Hurtado de Mendoza.

The citizens appealed to France, who sent them the great Marshal, Piero Strozzi, brother of Cosimo's vanquished enemy Filippo.
Cosimo through these years supported the Spanish cause with troops and money, hoping to guide events in his own interest.