The Fortress was permanently given to the Salimbeni family in 1274, which was followed by a period of struggle, resulting in clashes between various Sienese families. In 1380, Catherina of Siena was said to have stayed here while she carried out the secret mission of convincing the Salimbeni to make peace with the city. According to Raimondo da Capua, author of The Life of Catherine, this is where the saint received the gift of writing. The war ended in 1419, when Giovanni Zolla opened the gate at night and brought in the Sienese. Cocco dei Salimbeni took shelter in the tower with a small group of his followers, including his wife and family. One tragic night, in an episode straight out of a Shakespearean tragedy, Cocco successfully resisted every assault launched at him. In the end, however, his subjects gathered together and decided they wanted “to be governed in the same way as others in the district,” and thus swore allegiance to the Republic, forcing Salimbeni to surrender.
The fortress became a stronghold for the Sienese, who used the building to protect themselves during raids carried out by Cesare Borgia, Valentino di Machiavelli (1502) and Fabrizio Maramaus a few years later. In 1553, its inhabitants surrendered to Charles V’s troops without a fight, but they retook the fortress just a few months later. However, this didn’t prevent the Imperialists from regaining the territory, which they did by destroying dozens of houses and setting fire to the castle, ultimately bringing about the fortress’s decline.