AUBUSSON, PIERRE D' (1423-1503), grand master of the order of St. John of Jerusalem, was a scion of a noble French family, and was in early life a soldier of fortune under the emperor Sigismund. On his return to France he fought with the Armagnacs against the Swiss, distinguishing himself at the battle of St. Jacob (1444). He then joined the order of the Knights Hospitallers of St. John of Jerusalem, becoming grand master in 1476. The defence of Rhodes against the fleet of the sultan Mohammed II. in 1479 made Aubusson famous through out Europe. His treacherous conduct toward Jem, brother of Mohammed's successor, the sultan Bayezid, is a stain on Aubus non s memory. After Jem's defeat by his brother he took refuge at Rhodes under a safe-conduct from the grand master; Aubusson nevertheless accepted a bribe from Bayezid, and after six years' imprisonment Jem was handed over to Pope Innocent VIII. Aubusson's reward was a cardinal's hat (1489), and the power to confer all benefices connected with the order without the sanction of the papacy; the order of St. John received the wealth of the suppressed orders of the Holy Sepulchre and St. Lazarus. The remaining years of his life Aubusson spent in the attempt to restore discipline and zeal in his order, and to organize a grand international crusade against the Turks. The death of Jem in had removed the most formidable weapon available against the sultan; and when in 1501 Aubusson led an expedition against Mytilene, dissensions among his motley host rendered it abortive. The old man's last years were embittered by chagrin at his failure, which was hardly compensated by his success in extir pating Judaism in Rhodes by expelling all adult Jews and forcibly baptizing their children.