ordered the Marquis de Villadarías to besiege the Plaza de Gibraltar. This first attempt to regain the city was unsuccessful and the Spanish army lifted the siege. However, to monitor the isthmus and to oppose a possible invasion of the rest of the territory, a permanent garrison was established in the area, under the military government of Campo de Gibraltar.
The Contravallation Line or La Línea de Gibraltar
Gibraltar was under constant surveillance and subject to the unsuccessful (1727 and1779 - 1783) sieges. After the 1727 siege, the Spanish government made a decision that would be crucial in the history of the future Línea de la Concepción: the construction of a line of fortifications, the "Contravallation Line" or "La Línea de Gibraltar" ("The Line of Gibraltar"), which would isolate the British outpost from the Spanish mainland.
An order was issued on 2 November 1730 to the Director of Engineering Prospero Jorge de Verboom, for the construction of two strongholds, one located to the east and the other at west of the isthmus, both united by a line of fortification, with the aim of preventing the movement and to assert rights over the isthmus, in addition to consolidate the Spanish presence in the area.
Construction began in 1731 on the two major strongholds, known as Santa Bárbara and San Felipe. The first was named in honor of the patroness of the Artillery, located at the east beach, where their remains are still visible. The second took its name to honor King Felipe V, and is situated on the beach at sunset. Between these two strongholds a large wall was built with various central square tip diamond shaped bulwarks with their respective bodies, running from Santa Bárbara to San Felipe. All of them were located at equidistant distances and were called Santa Mariana, San Benito, semi-square and body guard of San José, San Fernando and San Carlos.
