The educated Mariano IV, “Giudice” brought up in the court of Aragona

The 1323's Aragonese arrival in Sardinia was arranged the year before in Avignon, by the Aragonese king Giacomo II “il Giusto” (the Just) and the Giudice (Judge) of Arborea Ugone. The plan was the conquest and the partition of the territories that were still under Pisa-control. But the relationships between Arborea and Aragon quickly lost strength, leading to a war that lasted more than 60 years, and to the island devastation, finishing with the defeat of Sardinians in the battle of Sanluri, in 1409. Mariano IV d’Arborea and Pietro IV d’Aragona started the war.

The Giudice of Arborea Mariano IV brought up in the court of the Aragonese king. He was an educated man, able to speak different languages, and he was in correspondence with important personages of that time. Mariano never abandoned his expansion project, however, this was not for sure the only reason of the war. The violence of the Aragoneses against the Sardinians is very-well testified by the Rebeccu's massacre. The flag with the uprooted tree of Arborea became soon a point of reference for all Sardinians.

Mariano IV emanated the “Carta de Logu d’Arborea” and introduced important political and economic reforms. He also upgraded his army and fomented the revolt of the inhabitants of some localities ( the first was Alghero) against the Aragoneses. In 1364, moving diplomatically in line also with the Pope, Mariano IV tried to assume the ordinance of the Sardinia's Reign in lieu of Peter IV. In 1365, not obtaining the hoped results, he attacked the castle of Sanluri and immediately after the castle of Cagliari. The expansion of Arborea seemed to be endless, so as the Aragonese decadency. Unexpectedly, in 1376, Mariano IV died of a dreaded disease - perhaps the plague. His son Ugone III. replaced him.