The republicans of Florence, with the aid of the French, had driven out Giuliano's brother Piero di Lorenzo de' Medici in 1494. The republicans, however, fought among themselves; and the French alliance, to which the republic remained faithful, led to the political isolation of Florence when Pope Julius II organized his Holy League against France's king Louis XII. In 1512 the Pope demanded that Florence enter the league, dismiss its current leaders, and allow the exiled Medici to return. Florence was forced to submit by a Spanish army, which sacked Prato. Giuliano, who returned with his Medici kin in September 1512, used harsh measures to suppress a conspiracy but generally showed moderation during his short reign. In 1513, however, his older brother Cardinal Giovanni became pope as Leo X; and Giuliano, himself a cardinal and appointed gonfalonier of the Holy Roman Church, went to join him in Rome. In 1515 he received the French title of duc de Nemours.