Battle of Campaldino The Battle of Campaldino was a battle between the Guelphs and Ghibellines on 11 June 1289 . Mixed bands of pro - papal Guelf forces of Florence and allies , Pistoia , Lucca , Siena and Prato , all loosely commanded by the paid " condottiero " Amerigo di Narbona with his own professional following , met a Ghibelline force from Arezzo including the perhaps reluctant bishop , Guglielmino degli Ubertini , in the plain of Campaldino , which leads from Pratovecchio to Poppi , part of the Tuscan countryside along the upper Arno called the Casentino . One of the combatants on the Guelph side was Dante Alighieri , twenty - four years old at the time . Background to the battle . Later , in the mid - 14th century , Giovanni Villani recorded the long - remembered details — as Florentines remembered them — in his chronicle , though the " casus belli " he offers are merely conventional " outrages " on the part of Arezzo ; the elaborately staged raid and fight led by aristocrats on both sides sounds like stylized gang warfare , though carried out , according to Villani , under the battle standard of the absent Charles , the Angevine King of Naples . The immediate cause of the battle were reports that the Guelphs were ravaging the places of Conte Guido Novello , who was podestà of Arezzo , and , worse , threatening the fortified place called Bibbiena Civitella . This led to an Arentine force being quickly assembled and marching out to counter the threat . It was reported by Villani that a plot had been intercepted at Arezzo , by which the bishop agreed to give over to the Florentines Bibbiena Civitella , and all the villages of his see , in return for a life annuity of 5 , 000 golden florins a year , guaranteed by the bank of the Cerchi . The plot was uncovered by his nephew Guglielmo de ' Pazzi , and they hustled the bishop onto his horse and brought him to the battlefield , where they left him dead among the slain of the battle and its aftermath : Guglielmino de ' Pazzi in Valdarno and Buonconte , the son of Guido I da Montefeltro . The armies . The Florentines and their allies had 10 , 000 undisciplined armed rabble on foot , including light - armed infantry , and crossbowmen , and unmounted lancers , but 1 , 600 knights and 600 mounted burghrers of Florence , the best armed and mounted which ever sallied out forth from Florence ; and 400 mercenaries , together with the following of the Captain M [ esser ] Amerigo , in the pay of the Florentines ; and of Lucca there were 500 horsemen ; and of Prato 40 horsemen and foot soldiers ; and of Pistoia , 60 horse and foot ; and of Siena , 120 horse ; and of Volterra , 40 horse ; and of Bologna , their ambassadors with their company ; and of Samminiato , and of Sangimignano , and of Colle , men mounted and on foot from each place ; and Maghinardo of Susinana , a good and wise captain in war , with his Romagnoli . The forces were equal as far as the large groups of foot - soldiers were concerned ; the mounted knights of the Aretine forces only came to 800 , but those were " the flower of the Ghibellines of Tuscany , of the March , and of the Duchy , and of Romagna ; and all were men experienced in arms and in war " ( Villani ) . The battle . Deployment . The Florentines deployed an advance guard of cavalry , behind which , in the centre of their line stood the bulk of their cavalry . On each wing they placed their infantry , slightly forward so the line was crescent shaped . Behind this force , they drew up their baggage and , behind that , a reserve of infantry and cavalry . The Arentines drew up in four lines ; the first , second and fourth of cavalry , the third of infantry . The course of the battle . The Arentines attacked with their first three lines , scattering the Florentine advanced guard and pushing back the main body towards the wagons . However , they now came under crossfire from the flanking infantry . The Florentine reserve now made a flanking attack , trapping the Aretines . According to Villani , Corso Donati , podestà of Pistoia . though under orders to stand ready in reserve , shouted “ If we lose , I will die in the battle with my fellow citizens ; and if we conquer , let him that will , come to us at Pistoia to exact the penalty ! ” and charged the Aretine flank , helping break up the lines and win the day for the Guelphs . Instead of coming to the rescue , the Aretine reserve fled . Aretine casualties were high . Ploughing the Campaldino plain used to turn up human remains and bones as recently as eighty years ago Result of the battle . The Battle of Campaldino secured the Guelphs in Florence , though internecine fighting among the Whites and Blacks among the Florentine Guelphs resulted in civic disturbances and the exile of many , including Dante ( a member of the Whites , the faction more opposed to papal power ) .