Guido II da Polenta, the nephew of Lamberto I da Polenta, had acquired the lordship of Ravenna after the latter's death.

In 1316–1321 he was host of Dante Alighieri.

In 1322 he is named capitano del popolo of Bologna and leaves the government of Ravenna to his brother Rinaldo, who was archbishop of the city though without the Papal confirmation.

Ostasio I da Polenta, from the family line of Cervia, profited of the situation to kill Rinaldo and seize the power for himself.