The Cantelmo family, of French origins, arrived in Italy in the 13th century around the time the
Angevins conquered Naples (1266). From the Angevins, the Cantelmo received several castles and fiefs around
Alvito in what is now the
Valcomino, dominated by the numerous fiefs of the powerful regional monasteries (such as
Monte Cassino and
San Vincenzo al Volturno), as well as by the rival family of the Counts of Aquino. Rostaino and his successors tried unsuccessfully to extend their control over the whole region in the 14th century. They sided with Queen
Joan II of Naples but were defeated by the troops of
Charles of Durazzo. In a document of 1384, Giacomo IV is mentioned as "lord of the lands of Alvito". During the turmoil caused by the succession of
Ladislaus of Naples, the Cantelmo sided with his rival,
Louis II of Anjou.
Rostainuccio ("little Rostaino") was defeated and captured by Jacopo Orsini at
Pereto in Abruzzo in 1369, and Alvito was granted by Ladislaus to
Andrea Tomacelli, brother of the
Count of Sora and of
Pope Boniface IX. Alvito was soon returned to the Cantelmo, and
Giacomo V, Rostainuccio's son, was the first ruler of Alvito to bear the title of
count. He likely obtained the title as a
dowry from his wife, Elisabetta d'Aquino. After Giacomo's death the county was expanded by his son
Antonio, who acquired
Gallinaro,
Fontechiari,
Arce,
Popoli (this from his brother Francesco, who had died heirless), and other lands in the Abruzzo and Valcomino. Antonio's rule was troubled by the turmoil and succession crises of the Kingdom of Naples in the early 15th century, and he lost his lands repeatedly. His son
Nicolò was able to establish his rule more firmly by backing the successful
Alfonso V of Aragon in his conquests of 1443. Alfonso created Nicolò
Duke of Sora, and in this capacity he stripped his brother Onofrio of the County of Popoli in Abruzzo. Nicolò also obtained the position of royal counselor in 1452 and, just before his death, his title was raised to Duke of Alvito. Nicolò's son
Piergiampaolo inherited Sora and Alvito, while another son,
Piergiovanni, inherited Popoli. Piergiampaolo soon annexed his brother's Abruzzese lands and, after siding against the new king,
Ferdinand I, in the revolt of 1460, captured the territories of Montecassino, Arce, and the fiefs of the
Colonna in Abruzzo. He also took part in the sieges of
Sulmona and
L'Aquila, but was in turn besieged and defeated by
Napoleone Orsini at Sora. As a result, he was forced to cede Sora,
Arpino,
Casalvieri,
Isola del Liri, and
Fontana Liri to the
Papal States in 1463. His duchy was downgraded to a county, the title being assigned to Piergiovanni. At the same time, Alvito and Sora were given the right to mint
cavalli (a type of coin). Piergiampaolo organized a second plot against Ferdinand, but was again defeated and had to abandon hopes in returning to Alvito. Exiled to France, he returned with the invading army of
Charles VIII of France during the
War of 1494–95. With his brother, Sigismondo II of Sora, he re-conquered most of his lands. He was able to resist the Neapolitans after the French retreat, but in 1496 Sora fell to
Frederick I of Naples, followed in 1496 by Alvito, captured by general
Gonzalo de Córdoba. This put an end to the Cantelmo rule. ==Royal demesne==