The Terzi of Parma, belonging to the Emilian rural nobility, also reported in the XIV century as podestà, captains and governors of the Po Valley, were first Counts of Tizzano and then lords, at different times, of the city of Parma and Reggio.
The Terzi descended from the Ghibelline family of the Da Cornazzano. As the founder, we mention a Gerardo Tercius, also identified as "Terzo da Cornazzano" and so called as the third-born of Pietro, the founder. The same is also remembered by the Annales Cremonenses as "Bernardo da Cornazzano" (1218) and cited by other sources cite as Bernardo or "Gherardo Tertius" (1223).
Di Gherardo two sons are known: Pietro and Guido. The latter appears in a document of 1248 among the Guelphs of Parma. He had as his sons Filippo and il Guidone, listed in 1311 as "Guido Tercius" among the most eminent citizens of Parma. Guidone and Filippo, are explicitly referred to as "de Tertiis" in the imperial diploma issued to them in 1329 by Ludovico il Bavaro.
With that imperial diploma, the Parma Terzi established their autonomous stately presence, which must already have been well established, even economically, in the Parma countryside, at the mouth of the Taro, between Sissa and Torricella. Chronologically this institution is placed in the fourteenth century in harmony with the tendency to revive the so-called lordship of banno, where the lord took the burden, with the privileges, to govern the territory with full jurisdiction. This favored the establishment of new centers of power, as well as in Parmigiano, in the Po Valley and generally in central-northern Italy ".
The Terzi had already been invested, as Cornazzani, by Frederick II of Swabia, in 1247, as counts of Tizzano Val Parma and Belvedere (today Castelnuovo Fogliani) and other lands in Parmigiano. Thus they became successively and alternately over time lords of Parma, Noceto, Guardasone, Colorno.
The Terzi deployed every means to expand their dominion over more and more important territories, from Parma to Piacenza and Reggio Emilia. To this end they bound the ambitions of the family to those of the Duchy of Milan, until this was the Visconti. Thus in 1364 the brothers Niccolò Terzi il Vecchio and Giberto Terzi swore allegiance to Bernabò Visconti. Niccolo the Elder then purchased in 1375 from Gherardo Visconti in Piacenza, the jurisdictions of Castelnuovo and Casale Albino. These were subsequently confirmed by Gian Galeazzo Visconti, the Duke of Virtù, who in 1386 recognized even greater immunity to Tizzano Val Parma.
The agreement of the Terzi with the Visconti is confirmed by the assignment of numerous Rectorates in the Po Valley cities, such as the regency of the Council of Verona for the ultra Mincium parties, as well as the captains of Bergamo, Brescia and Reggio nell'Emilia. Significant is also the extent of honors granted with the diploma of Emperor Wenceslas of Luxembourg (1387), which allowed Niccolò il Vecchio, with the right of transmission to the children, the title count. The solemn ceremony with which Niccolò was awarded the military track was celebrated in the cathedral of Pavia on August 15, 1387. The privileges attributed by that imperial diploma, it was observed, "appear hardly imaginable outside of an agreement with the Count of Virtue, in forbidding the impetus of papal or imperial privileges without his special license, and by now able to impose his own preventive placet upon the powerful emilian dominions, even only for the exercise of a podesta or a conduct outside the domain.
Fidelity to the Dukes of Milan deserved to the family in following times, that is to the leaders Niccolò Terzi il Vecchio, to the sons of these Giacomo Terzi, Ottobono or Ottobuono de 'Terzi and to the nephew Niccolò Terzi, the Warrior, in addition to the huge assets held in Parma, the castles of Guardasone, Bazzano, Colorno, and other lands such as Nigone, Montelugolo, Scalucchia. In the Reggiano there were the fortresses of Rossena under Canossa, Sassatello and Gombio. Benefits that were added to the extensive agricultural properties owned ex long-lasting tempore between Castelnuovo di Sotto, Medesano, Gualtieri and Guastalla.
When in July 1450 Francesco Sforza, succeeded to Filippo Maria Visconti in the Duchy of Milan, dispossessed Niccolò Terzi called the Warrior of the Lordship of Parma and of the lands owned in Castelnuovo, Lusurasco and Saliceto di Chiaravalle, near Alseno, Bagnolo in Piano, Noceto and Santacroce , all the dominion of the Terzi in the Po valley ceased. Nicholas the Warrior abandoned the Milanese state and found refuge at the Gonzaga court in Mantua.
A cousin of the "Guerriero", Gian-Filippo, son of Giacomo Terzi, settled in the Marche, where he gave rise to the family of the Marquis Guerrieri di Fermo. The Warriors of Fermo, called to the court of the Gonzaga of Mantua, originated the family of the Gonzaga Warriors. This decreed the Gonzaga "the penultimate aprilis 1506" when he wanted that the great-grandson of Giacomo Terzi, Lodovico Guerrieri, was aggregated to his House and assumed since then for himself and descent the surname "Guerrieri Gonzaga". The same Lodovico was appointed in 1514 marchionalem consocium beneamatum and in 1522 became Lieutenant General of the Lords of Mantua and Urbino.
A branch of the Terzi, descendants of Ottobuono de 'Terzi and the son of these Gio-Francesco (or Giovanni Francesco), was enfeoffed in the Parmigiano with the Terzi di Sissa, county from 1450 to 1805. This line of the Terzi, succeeding the Venetians they had occupied it, rebuilt in 1440 the male of the fortress, after it had been almost destroyed in the clashes with the Rossi of San Secondo. In the eighteenth century this branch of the Terzi family became extinct in the Rangoni family of Modena.