1559 conclave

The 1559 papal conclave (5 September – 25 December) was convened on the death of Pope Paul IV and elected Pope Pius IV as his successor. Due to interference from secular rulers and the cardinals' disregard for their supposed isolation from the outside world, it was the longest conclave of the 16th century.

Pope Paul IV died on 18 August 1559, aged 83. His church reforms had mainly been based on repressive measures such as the Inquisition and the Index of Forbidden Books – he had no confidence in the Council of Trent, dissolving it in 1552 and not reviving it.

Even cardinals were accused of heresy – at the time of Paul IV's death, Cardinal Morone was a prisoner of the Inquisition in the castel Sant' Angelo. Paul IV, fearing that Morone might become his successor, issued the papal bull Cum ex officio Apostolatus, which stipulated that a heretic could not be validly elected pope – however, this was in vain since the College of Cardinals released Morone after Paul's death and allowed him to take part in the conclave. The bull also covered Cardinal d'Este, who Paul complained was trying to become pope by simony.

Paul IV's reforms did not abolish nepotism, however – 3 of the cardinals at the conclave were Paul's nephews, the most influential being Carlo Carafa and the other two being Diomede Carafa and Alfonso Carafa. On the model of pope Alexander VI (one of the Borgia popes, who had died on the same date as Paul 56 years earlier), Paul had tried to build up his family's power in Italy, mainly at the expense of the Colonna family, whose many lands (including the imperial Palia fiefdom) were seized and handed over to the Carafa family. Paul's nephews ruled even more brutally than he and abused their power so much that at one point Paul was forced to step in, stripping Carlo of power early in 1559. Carlo never regained his uncle's favour and after Paul's death he and Paul's other two cardinal-nephews had good reason to fear their enemies would now take revenge.

Paul IV was rigidly orthodox, intolerant, and authoritarian in manner. Spontaneous riots broke out in Rome after his death, with crowds toppling his statue and attacking the Inquisition's headquarters. Thus 3700 troops were brought in to keep order, including 300 cavalry.

At the time of the conclave there were 55 cardinals, 47 of whom participated in it. Of those 47, one died during the conclave (Capodiferro) and two had to leave early due to illness:

Of these 47 cardinals, 37 were Italians, 7 French, 2 Spanish and 1 German. 13 had been appointed by pope Paul IV, 11 by pope Julius III, 20 pope Paul III, 2 by pope Clement VII and 1 by pope Leo X.

8 cardinals (5 French, 1 Spanish, 1 Portuguese and 1 Italian) did not come to the conclave. 2 of these 8 died during its sitting: