Charles Eliot Norton, in his prose translation of Dante's Inferno, Canto XXXIII, supplies us with this note:
In July, 1288, Ugolino della Gherardesca, Count of Donoratico, head of a faction of the Guelphs in Pisa, in order to deprive Nino of Gallura, head of the opposing faction, of the lordship of the city, treacherously joined forces with the Archbishop Ruggieri degli Ubaldini, head of the Ghibellines, and drove Nino and his followers from the city. The archbishop thereupon took advantage of the weakening of the Guelphs and excited the populace against Ugolino, charging him with having for a bribe restored to Florence and Lucca some of their towns of which the Pisans had made themselves masters. He, with his followers, attacked Count Ugolino in his house, took him prisoner, with two of his sons and two of his grandsons, and shut them up in the Tower of the Gualandi, where in the following March, on the arrival of Count Guido da Montefeltro (see Canto xvii), as Captain of Pisa, they were starved to death.