Antonio Todeschini Piccolomini, after the first years dedicated to his studies at Sarteano, turned to the craft of arms, like many other members of his family. Under the guidance of his uncle Pope Pius II, he took care of the Church's interests, in the still fragile Aragonese monarchy of Ferdinando I (Ferrante) of Aragon. The latter, the natural son of the late Alfonso V, was favored by the Pope, who enshrined his inheritance right in the Neapolitan monarchy, against the Angevin pretender Giovanni di Lorena.
In this situation of political instability and in the need to consolidate the alliance with the papacy, the marriage between Antonio and Maria, the natural daughter of the Aragonese King, was decided. Circumstance that opened to the Sienese family, new horizons in the south of the peninsula. The eldest son of Laudomia, thus obtained the nomination to Duca d'Amalfi and was able to add to his own, the surname of the Aragonos and to have his coat of arms inscribed with the royal insignia. In the same year, 1458, he was also nominated Grand Giustiziere of the Kingdom of Naples and the family was attached to the Neapolitan patriciate in the Seggio di Nilo, one of the seven Seats of Naples. The expectations were not disappointed and Piccolomini, with its militias, played a decisive role in the acquisition, the monarchy, of Castellammare di Stabia and Scafati. On 18 August 1462 under the command of Alessandro Sforza, and at the head of 2000 infantry and 26 teams of horses, he took part in the battle of Troy. The Angevin rival of Ferrante I was finally defeated, along with the rebel feudal lords of the kingdom. It was thus given to the anti-Aragonese movement, the so-called Conspiracy of the barons, a coup de grace from which it will fail, more to recover.
After the victory of Troy, he benefited from the distribution of numerous fiefdoms that the Ferrante assigned to the defenders of his cause. In 1463 he obtained the title of marquis of Capestrano and of Deliceto, the title of count of Celano and Gagliano, the title of baron of Balsorano, Pescina and Carapelle; in 1465 he finally became baron of Scafati.
Simultaneously with these events in 1462, in the continuous controversies that affected the Marche region, Malatesta definitively lost the Lordship of Senigallia by Guido da Montefeltro, who returned it to the Papal States. The then pontiff Pious II gave it in dominion, together with the lordship of Moldavio to his nephew Antonio. In 1474, however, Giovanni Della Rovere, nephew of Pope Sixtus IV, who succeeded in the various nepotistic games, succeeded in these fiefdoms.
Piccolomini's interests now gravitated in the kingdom of Naples, where the political offices, the administration of the innumerable fiefdoms, which, among other things, brought economic returns of no little interest, absorbed him completely. During the twenty years of peace that followed, he built the castles of Balsorano, Celano and Ortucchio and restored several others of his property which he then distributed among his descendants.
It should be emphasized that the figure of Antonio has an exemplary dimension. Unique in all his family showed great sensitivity towards the development of Amalfitan manufacturing. In virtue of his industrious culture, inherited in the Sienese territory, and also to the politics inaugurated by Alfonso V of Aragon, he imported, from different places of the peninsula, masters able to give impulse to the construction of different factories.
First of all it was the one for the processing of wool "used in Siena and Florence", as well as several fulling mills and dye works in the Amalfi area: in Scala, Pontone, Ravello, Strani and Maiori. He relaunched and implemented the preindustrial steel plants, the ironworks, already present in Amalfi.