Florence–Papal Conflict after the Pazzi Conspiracy (1478)

Timeline

1. c. 1478Rome · RomeSixtus IV refused to accept Florence's explanation of the Pazzi Conspiracy, excommunicated Lorenzo de' Medici and the principal officials, and imposed an interdict on the entire city of Florence, forbidding the celebration of sacraments. This isolated the Medici regime in terms of religious authority and provided a moral pretext for military intervention.
2. 1478–1479Southern border of Tuscany · TuscanyFerdinand I led Neapolitan forces northward, while Papal States troops also pressed from the south. Florence levied militia and relied on condottieri such as Cost da Mottola to resist. Lorenzo personally went to Naples (1479–1480) for diplomatic mediation, while Venice tied down papal forces within the framework of the War of Ferrara.
3. 1479–1480Naples and Florence · NaplesLorenzo visited the Neapolitan court and, through personal charm and political promises, persuaded Ferdinand to halt the offensive. The papacy, preoccupied with the War of Ferrara and Venetian pressure, could not devote its full strength against Florence, and the interdict was gradually relaxed. The conflict was not fully resolved by treaty, but the Florentine regime survived, and Lorenzo's status as "the Magnificent" was further consolidated.