Peter I of Arborea

In the late 1190s, Constantine II of Logudoro and his son Comita III, allies of Genoa, warred with Peter, who was under the protection of William I of Cagliari.

Comita eventually sued for peace with Pisa and abandoned his claims over Arborea in exchange for the castle of Goceano, held thitherto by William.

Pope Innocent III, in a letter of 11 August, launched an investigation of the church's participation in this usurpation, which Giusto, Archbishop of Arborea, claimed the canons of Oristano had no authority to effect.

Unbeknownst to the pope, he had made a secret pact with Hugh whereby he retained control not only of Peter's half of Arborea, but also of all the fortresses in the realm.

Peter died a prisoner in Pisa and his son Barisone inherited his half of Arborea, after being freed from imprisonment to marry William's heiress, Benedetta.