Giovanni Fieschi, bishop of Vercelli and Guelph leader was also a military chieftain. In 1371, he marched upon Genoa at the head of eight hundred horse to avenge his family who as rebels had been dispossessed of the castle of Roccatagliata by the Republic. He waged a long war with the Visconti. They had robbed him of Vercelli, but he reacquired this feud by subsequent treaty. He obtained from the Pope the temporal sovereignty of that city; and Boniface IX and his successors invested him with Montecapelli, Masserano and Crevacore. After his death, Vercelli passed into the hands of his nephew Gianello, of good fame both as a cardinal and warrior. It was by his influence and that of Giacomo Fieschi, Archbishop of Genoa, that the Republic undertook to rescue Urban IX when he was besieged in Nocera di Puglia. Nor were Guglielmo and Alberto Fieschi without military celebrity. They conquered the kingdom of Naples for their uncle Innocent IV. Not less warlike were Emanuele and Giovanni Fieschi, who as bishops and lords governed Biella in the middle of the fourteenth century. Giovanni, however, had the misfortune to incur the displeasure of his people, was driven from power, and ended his days in prison, 1377. The civil life of Genoa for many centuries was a succession of political revolutions. The leading spirits were always the Fieschi and Grimaldi, Guelphs, and the Spinola and Doria, partisans of the Empire. Carlo Fieschi was certainly a turbulent spirit and a promoter of discord. In order to remove from power the opposite party, he handed the Republic over to Robert of Naples, and Francesco Fieschi attempted to give Genoa to his son-in-law the marquis of Monferrato. Francesco had fought as Guelph general against Opizzino Spinola and the marquis of Monferrato had given him valuable aid in the campaign which he successfully closed by burning Busalla and desolating the Spinola estates.
But Francesco exercised the rights acquired by conquest with a moderation unusual in those times; and he committed the government of the city to sixteen citizens.
For the rest, the Fieschi though sometimes turbulent and dangerous to the peace of the city, never laid violent hands on the liberties of the Republic. Their struggles aimed to emancipate the city from the influence and control of the imperial party, and they always faithfully served those to whom they offered their arms.