1451 Nicholas begins great building operations.
1452 Nicholas crowns Frederick III emperor. Cardinal Isidore and a small force are sent to the relief of Constantinople.
1453 Plot of Stefano Porcaro to re-establish the Roman Republic. It fails, and Porcaro is exiled. The Ottoman conquest of Constantinople brings many learned men to Rome, who assist in the Renaissance. Nicholas proclaims a crusade against the Turks.
1454 League of Lodi.
1455 Alfonso Borgia, Calixtus III. His election is unpopular.
1456 Calixtus proclaims war against the Turks. The papal fleet is sent, but only wins a few unimportant victories.
1458 At death of Alfonso of Naples, Calixtus claims Naples, which he wants for a fief for his nephew, Pedro. These plans are terminated by Calixtus’ death. Æneas Sylvius Piccolomini, Pius II. He recognises Ferdinand as king of Naples.
1459 Congress of Mantua. Pius dreams of converting Muhammed to Christianity.
1460 Publication of the bull “Execrabilis” in which appeals to future councils are condemned. Revolt of Tiburzio in Rome. Pius returns from Mantua and subdues it.