Pope from 1271. He recognized Rudolf of Habsburg as Emperor, inducing Alfonso of Castile to resign his claims to the German throne. At the Second Council of Lyons (1274) the Greek Emp. Michael Paleologus made his submission to the Pope, though the reunion was short-lived. Among the innovations of his pontificate was the introduction in 1274 of the conclave in Papal elections. Feast day, 9 Jan.