[1] Though many clashes between Guelphs and Ghibellines loomed larger to contemporaries than to historians, the unusually-large encounter involved 4,000 estimated cavalry and some 35,000 foot soldiers, and 2,000 men lost their lives.
In 1296, the Bolognese invaded the Modenese lands of Bazzano and Savigno, with the support of Pope Boniface VIII, who recognized in 1298 Guelf possession of the border castles.
In Modena, the struggle for power after the death of Obizzo II d'Este, which divided his sons' friends into hostile camps, was resolved in favor of Azzo VIII, who confronted Bologna partly to bolster his lukewarm reception by his own city's nobles.
His elected successor, the Mantuan Passerino Bonacolsi, the agent of Louis of Bavaria, King of the Romans,[2] pursued the embittered war politics, with Parma, Reggio and Modena also under his power.
[5] As the Bolognese chronicler Matteo Griffoni tells it,[5] the militia and the rabble of Bologna headed by their podestà, aided by allies from Florence and Romagna, besieged the fortress of Monteveglio.
The Modenese advanced to the very walls of Bologna and destroyed the castles of Crespellano, Zola, Samoggia, Anzola, Castelfranco, Piumazzo and the chiusa del Reno near Casalecchio, which diverted the river towards the city.
They did not attempt a siege of the city but scornfully organized a palio outside the very gates of the city ad æternam memoriam præmissorum et æternam Bononiensium scandalum, "to the eternal memory of those sent out on the expedition and the eternal shame of Bologna",[7] and then returned to Modena brandishing a bucket taken from a well outside Porta San Felice; twenty-six captured notables of Bologna were incarcerated for the next eleven weeks in Modena.
At Bologna, the coat of arms of Pope John XXII was displayed in conjunction with those of Robert d'Anjou, showing that the old alliance of the Avignon papacy and the house of Anjou was still viable in some eyes.