A carroccio was a large four-wheeled wagon bearing the city signs around which the militia of the medieval communes gathered and fought. It was particularly common among the Lombard, Tuscan and, more generally, northern Italian municipalities. Later its use spread even outside Italy. It was the symbol of municipal autonomy. Priests celebrated Mass at the altar before the battle, and the trumpeters beside them encouraged the fighters to the fray.

Medieval communes in the European Middle Ages had sworn allegiances of mutual defense among the citizens of a town or city. These took many forms and varied widely in organization and makeup.