In 1538 after defeat at the battle of Preveza, the Habsburg admiral Andrea Doria led his fleet in a successful attack on the Ottoman fortress at Herceg Novi on the Adriatic coast 600 kilometers to the northwest. According to the Ottoman naval historian Katib Celebi, the castle warden, or dizdar, did not defend the castle vigorously but after a few days surrendered. Even more puzzling is that the dizdar’s daughter married a captain in Doria’s fleet, a nobleman named Cigala. The thesis of this paper is that relying solely on narrative histories, the actions of the dizdar and Cigala seem inexplicable, but after viewing in person the fortifications at Herceg Novi their motivations become understandable. Comparing the fortifications of the castle that was surrendered in 1538, with the fortifications of the new fortress that the Ottomans built in 1539 after they retook the location provides valuable insights. Herceg Novi’s fortifications were outdated in 1538: built in the fifteenth century they were adequate for protecting against brigands, but useless against a fleet with state-of-the-art artillery. When Doria arrived with his well-armed fleet, there was no defense that the dizdar could make with a small garrison in this fortress whose thin walls were not built to withstand artillery fire. Therefore, he chose to negotiate and get the best terms he could for himself and his daughter. When the Ottomans retook the strategic port in 1539, they built state-of-the-art fortifications to withstand artillery fire, including platforms for their own artillery. Comparing the walls of the two fortresses at Herceg Novi with the historical record, we can make sense of the decisions made in the past by the participants in the siege. In addition to Katib Celebi’s naval history, later documents, such as found in the Calendar of State Papers, record information about this event, because the son of Cigala and the dizdar’s daughter, later became the Ottoman admiral Cigalazade. For comparison, the walls of Jerusalem, constructed by Suleyman 1537-41 are useful for they were not built to withstand artillery but were of greater symbolic than military value. Analyzing photographs of fortresses and walls, while analyzing documents and histories, I evaluate the fortresses’ military effectiveness, which constrained decisions made in 1538.