This was the sanction of the Pazzi Conjuration against Giuliano and Lorenzo de' Medici.

In the year 1477 the Medici, after excluding the merchant princes of the Pazzi family from the magistracy at Florence and otherwise annoying them, had driven Francesco de' Pazzi in disgust to Rome.

Sixtus chose him for his banker in the place of the Medicean Company.

He became intimate with Girolamo Riario, and was well received at the Papal Court.

Political reasons at this moment made the Pope and his nephew anxious to destroy the Medici, who opposed Girolamo's schemes of aggrandizement in Lombardy.