Guglielmo or Guglielmino Ubertini ( – Campaldino, 11 June 1289) was an Italian

condottiero Condottieri (; singular: ''condottiero'' or ''condottiere'') were Italian military leaders active during the Middle Ages and the early modern period. The term originally referred specifically to commanders of mercenary companies, derived from the ...

(military leader) and

bishop of Arezzo The Diocese of Arezzo-Cortona-Sansepolcro () is a Latin diocese of the Catholic Church. It has existed since 1986. In that year the historic diocese of Arezzo was combined with the diocese of Cortona and the diocese of Sansepolcro, the enlarged ...

. He died in the

Battle of Campaldino The Battle of Campaldino was fought between the Guelphs and Ghibellines on 11 June 1289. Mixed bands of pro-papal Guelph forces of Florence and allies, Pistoia, Lucca, Siena, and Prato, all loosely commanded by the paid ''condottiero'' Amerigo di ...

, leading a force of mainly Aretine

Ghibellines The Guelphs and Ghibellines ( , ; ) were factions supporting the Pope (Guelphs) and the Holy Roman Emperor (Ghibellines) in the Italian city-states of Central Italy and Northern Italy during the Middle Ages. During the 12th and 13th centurie ...

fighting against a victorious Guelf army from Florence, Lucca, Siena, Pistoia and Prato.

Dante Alighieri Dante Alighieri (; most likely baptized Durante di Alighiero degli Alighieri; – September 14, 1321), widely known mononymously as Dante, was an Italian Italian poetry, poet, writer, and philosopher. His ''Divine Comedy'', originally called ...

putatively fought with the victorious army. Guglielmo, with the support of the

Holy Roman Emperor Frederick II Frederick II (, , , ; 26 December 1194 – 13 December 1250) was King of Sicily from 1198, King of Germany from 1212, King of Italy and Holy Roman Emperor from 1220 and King of Jerusalem from 1225. He was the son of Emperor Henry VI of the Ho ...

, was confirmed bishop in 1256 by pope Alexander IV. Guglielmo with the support of warriors from

Spoleto Spoleto (, also , , ; ) is an ancient city in the Italian province of Perugia in east-central Umbria on a foothill of the Apennines. It is south of Trevi, north of Terni, southeast of Perugia; southeast of Florence; and north of Rome. H ...

and the Marche, had defeated in 1288 the Sienese at Pieve del Toppo. Controversy exists as to how willing Guglielmo was to battle the Guelph army at Campaldino. Some sources state he was forced onto the battlefield after attempting to negotiate with Florence. Others holds that Guglielmo, while urged to save himself at Campaldino, refused to leave the battlefield alive. His helmet and sword were displayed for many years in the church of San Giovanni in Florence.Dizionario biografico universale
Volume 5, by Felice Scifoni, Publisher Davide Passagli, Florence (1849); page 455-456.

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