The castle soon became the core of the new town of Preveza. People needed security in times of war, so it was only natural that they would leave their old settlement near the castle of Bouka, and set up home near the walls of the new fortification. The Ottomans had hardly finished working on it when the castle of Saint Andrew fell to the Venetians in 1718. They immediately embarked on a project of upgrading its defensive capabilities. They reduced its size to almost half and constructed a new moat. They also converted the mosque in the center of the castle into a Catholic church, in honour of Saint Andrew, the patron saint of the Venetian admiral who captured the town.