The Battle of Campaldino was fought 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
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 Aretine 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 family. 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 Bonconte, the son of Guido I da Montefeltro.
Opposing forces
Guelph army
The Guelphs had the numerical advantage in the battle, with about 12,000 combatants. Most of these troops had been raised by Florence, and were generally well-equipped due to their hometown's wealth. Florence was well known at the time as a producer of highly regarded weapons and armour, and its troops probably had better weaponry than the Ghibellines. The Florentines were reinforced by other Tuscan Guelphs, including Bologna, Pistoia, Lucca, San Gimignano, San Miniato, Siena, Volterra, and other small towns. Furthermore, small contingents of Guelphs from Romagna and Guelph exiles from Arezzo fought at Campaldino. The Guelph cavalry lacked combat experience and suffered from indiscipline, so that the about 10,000 infantrymen formed the actual core of the Guelph army. At least half of the infantry were better-trained specialists who operated as spearmen, pavisiers, crossbowmen, and archers, while the rest consisted of less effective, but still reliable militiamen. In general, the Italian Guelph troops were less experienced than the Ghibellines. In addition to these local forces, about 400 French knights of Amerigo di Narbona's retinue fought at Campaldino; they were experienced veterans who were highly regarded for their combat prowess.
The Guelph army was officially led by Amerigo di Narbona, who served as Charles II of Naples's representative for Tuscany and had been appointed as a compromise, since the Italian Guelphs could not agree on one of their own to lead them. Though he probably possessed some combat experience and proved to be a competent commander, Amerigo's relative lack of military skill, youth, and the fact that he did not speak Tuscan Italian meant that his command of the army was mostly nominal. As a result, the de facto leader of the army was a Carcassonne knight in Amerigo's retinue, Guillaume da Durfort, a highly experienced veteran of several wars. Under these two, several Italian Guelphs served as sub-commanders, with the most notable being Corso Donati, Vieri de' Cerchi, and the Barone de Mangiadori.