The defenses of Corsica in the second half of the sixteenth century. El Fratin's design for the citadels of Ajaccio and San Fiorenzo

In January 1563, Jacopo Paleari arrived in Corsica, and his worked from January 29 to December 26, with a brief interlude in Sardinia from May 20 to August 2. The task assigned to the engineer was to design new fortifications in coastal areas that were undefended and to improve existing citadels that were inadequate to withstand the attack of a treacherous enemy—already reportedly preparing for war, as suggested by the dense correspondence between chancelleries. At that time, the island’s defensive system was not suited to the new strategies of warfare. The only significant fortifications were in Calvi and Ajaccio, thanks to the efforts in the mid-1550s of Lombard specialists, among whom Giovan Maria Olgiati stands out. He had worked between 1539 and 1554 in Portovecchio, Bastia, Bonifacio, Ajaccio, and Calvi. El Fratino’s inspection work began in the Gulf of San Fiorenzo, where he designed the citadel and the ‘Mortella Tower’, and continued to Calvi and Ajaccio. Then he moved on to Bonifacio where he worked on the half bastion of the tower, and to Longon Sardo (modern-day Santa Teresa Gallura), reaching Sardinia on May 20 to inspect the construction sites in Cagliari and Alghero. After completing his inspection of the island fortresses, in July of the same year, he left Sardinia, passing once again through Corsica, where he visited Ajaccio, Bastia, San Fiorenzo, and Calvi. After stopping in Capraia, he arrived in Genoa on December 30 of the same year. A graphical analysis of his interventions reveals Jacopo’s use of well-defined design templates, where symmetrical forms adapted to the site can be identified, layouts developed with compass strokes, and constructional solutions that recall Leonardo’s early experiments for Piombino. His work also shows a strict application of the construction techniques described in the treatise Della fortificatione delle città by Girolamo Maggi and Captain Castriotto—a recognized design reference for the Ticinese engineer.