His literary pursuits were interrupted by a public duty. His friend Robert, king of Naples, died, and was succeeded by his daughter Giovanna, married to Andrea, prince of Hungary. [Sidenote: 1343. Ætat. 39.] The greatest dissension reigned between the royal pair; besides which, the young queen was not of an age to govern, and the pope had pretensions to supremacy during her minority. Petrarch was sent as ambassador to establish the papal claim; and he was commissioned, also, by cardinal Colonna, to obtain the release of some prisoners of rank unjustly detained at Naples. During this mission he became attached to the party of queen Giovanna, who inherited her father's love of letters; so that afterwards, when her husband was murdered, he believed her to be innocent of all share in the crime. He was displeased, however, with the court and the gladiatorial exhibitions in fashion there. Having obtained the liberty of the prisoners, and brought his mission from the pope to a successful conclusion, he returned to Parma. This part of Italy was in a state of dreadful disturbance, arising from the wars carried on by the various lords of Parma, Verona, Ferrara, Bologna, and Padua. Petrarch, besieged, as it were, in the first-named town, was obliged to remain. He had still the house he had bought, and the books he had collected and left in Italy. He loved his cisalpine Parnassus, as he named his Italian home, in contradistinction to his transalpine Parnassus at Vaucluse; and, occupying himself with his poem of Africa, he was content to prolong his stay in his native country. [Sidenote: 1345. Ætat. 41.] At length the roads became safe, and he returned to Avignon. And now an event occurred which electrified Italy, and filled the papal court with astonishment and disquietude. Nicola di Rienzi, inspired by a desire to free his townsmen from the cruel tyranny of the nobles, with wonderful promptitude and energy, seized upon the government of Rome, assumed the name of tribune, and reduced all the men of rank, with Stefano Colonna at their head, to make public submission to his power. The change he produced in the state of the country was miraculous. Before, travellers scarcely ventured, though armed and in bodies, to traverse the various states: under him the roads became secure; and his emissaries, bearing merely a white wand in their hands, passed unmolested from one end of Italy to the other. Order and plenty reigned through the land. The pope and cardinals were filled with alarm; while Petrarch hailed with glowing enthusiasm the restoration of peace and empire to his beloved country. He wrote the tribune letters full of encouragement and praise. His heart swelled with delight at the prospect of the renewed glories of Rome; and such was his blind exultation, that he scarcely mourned the death of several of the most distinguished members of the Colonna family, who fell in the straggle between the nobles and Rienzi.