[3] Although these fortifications were well designed, by the early 17th century they were not strong enough to resist a large attack due to new technological developments which increased the range of artillery.

Grand Master Antoine de Paule asked Pope Urban VIII for help in improving the island's fortifications.

The Pope sent Pietro Paolo Floriani to examine the defences, who in 1635 proposed building a second line of fortifications around the Valletta Land Front.

Some members of the Order and a number of military engineers strongly opposed these plans, since the large garrison needed to man the lines was deemed too expensive.

[5] Work on the lines began in 1636,[6] but no ceremony was carried out to commemorate laying the foundation stone due to controversy surrounding the construction.

[9] Fears of an Ottoman attack rose again after the fall of Candia in 1669, and the following year Grand Master Nicolas Cotoner invited the military engineer Antonio Maurizio Valperga to improve the fortifications.

[10] At the time the Floriana Lines were still under construction, and a number of weak points had been identified in their original design, especially since the demi-bastions forming the two extremities of the land front were too acute and could not be well defended.

[1] Work on Valperga's modifications to the lines progressed slowly, and by the beginning of the 18th century the outworks, glacis and enceinte facing Marsamxett were still unfinished.

[11] Works continued under a number of other engineers, including Charles François de Mondion, and the lines were largely complete when Porte des Bombes was constructed in 1721.

A number of minor alterations were made, including the enlargement of Porte des Bombes, the demolition of a lunette and some other gates,[14] and the addition of gunpowder magazines and traverses.