By 1417, the local militia had already established a permanent watch post on the tip of the Sciberras Peninsula. In 1488, the Aragonese built a watchtower on Saint Elmo Point, and it was dedicated to Erasmus of Formia, better known as Saint Elmo. In 1533, the Order of Saint John reinforced the tower due to its strategic location. In 1551, an Ottoman raid occurred in which the Turkish fleet sailed into Marsamxett Harbour unopposed. Due to this, it was decided that a major expansion was necessary, and in 1552 the tower was demolished and a new star fort began to be built. It was designed by a Spanish Engineer named Pietro Pardo. It had a cavalier, a covertway and a tenaille. A ravelin was hastily constructed months before the 1565 siege.