Last of the Spanish Renaissance men, Diego Hurtado de Mendoza (1504-1575) was a master of the humanist disciplines as well as an active diplomat whose correspondence provides insight into the workings of power politics in the first post-Machiavellian decades.

This account of Mendoza's diplomatic career is a living commentary on the mid-sixteenth century, the time of the Spanish Inquisition and the Reformation, with its upheavals in the European balance of power. Mendoza served as ambassador of Charles V to Venice and Rome and as governor of Siena. His political life complements the...