After Piccolomini had retired into private life, Lamberto Malatesta became the most formidable leader. He also was a man of rank and belonged to the family of Rimini who had once reigned almost as sovereign princes. His operations were conducted on a large scale and with the utmost audacity. He ravaged Romagna, Umbria and the Marches; he attacked and took fortified castles; he scaled the walls of Imola, an important town in the Romagna, and was strongly backed by the grand-duke of Tuscany, with whom he found secure winter quarters and all necessary reinforcements. The pope was constrained to threaten the duke with war unless he withdrew his support from this outrageous criminal. Sixtus spoke in the most indignant terms. “It astonishes me that you should tolerate a man who has been discarded by the Holy Church, that you should allow him to levy men in your states to the detriment of mine.” He went on to threaten coercive measures unless Malatesta was at once given up to him. The grand-duke yielded with a good grace; arrested Malatesta and sent him to Rome, where his arrival caused great consternation and a general exodus of many secret supporters who dreaded the result of his revelations. No better proof could be afforded of the extent of Malatesta’s nefarious operations and of the number of allies he had secured. It was said that at one time he had conceived the most ambitious schemes,--nothing less than the invasion of Italy by Protestant princes from the north and the overthrow of the papal power in Europe, in coöperation with his hordes of robbers. Sixtus made short work of this aristocratic criminal; he was put upon his trial, the suit was pressed forward and he was speedily condemned. Out of consideration for his family, the sentence of death passed upon him was carried out by decapitation on the battlements of St. Angelo. So efficacious were the uncompromising measures undertaken against brigandage that when barely two years had elapsed after the pope’s election, it had practically ceased to exist.