[9] 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.

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.

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.

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.

[12] 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.

[14] 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.

[18] The Ghibelline infantry consisted of fewer spearmen, pavisiers, and crossbowmen than its Guelph counterparts; instead, it relied on offensive close-quarters combat with swords and bucklers.

"A man of the sword as much as of the pen", Ubertini had proven to be a capable, ruthless, and brave military commander during several conflicts before 1289, though his strategic acumen was impeded by his interest in defending the possessions of his family at any cost.

Finally, there was Bonconte I da Montefeltro, an accomplished strategist and tactician who had led the Ghibellines to a "brilliant" victory at Pieve al Toppo in 1288.