(April 16, 1478) Unsuccessful plot to overthrow the Medici rulers of Florence.
It was led by the rival Pazzi family, with the backing of Pope Sixtus IV , who wanted to consolidate papal rule over northern central Italy. The conspirators tried to assassinate two Medici brothers during mass at the Cathedral of Florence; they killed Giuliano de' Medici, but Lorenzo de' Medici escaped. The people of Florence rallied to the Medici and killed many of the conspirators, leaving Lorenzo more powerful than before and setting off a two-year war with the papacy.