The Norman conquest of Campania forced the Dukes of Amalfi to modernize the structure to provide greater resistance to the enemy. The interior of the fortress was then extended with new features, including a chapel with a buttressed vault. Other additions from the thirteenth century included a cylindrical tower, two protective walls and other items necessitated by the development of siege techniques and firearms. In the fifteenth century, the island of Capri was subjected to attacks by Muslim pirates. Consequently, the population often used the fortress as a refuge. But after the raids in 1535, led by Ottoman pirates Hayreddin Barbarossa and Dragut, the fortress was destroyed in 1544, and those who had taken shelter there were kidnapped or robbed. Rather than being named after its builder, the castle derives its name from its pirate destroyer. The Angevins attempted to reconstruct the fortress, but without success as the Neapolitans had little building experience. It therefore fell on the inhabitants of Anacapri to care for the fortress which, as a result, was never rebuilt.