It was constructed during the Peninsular War, forming part of the first of three defensive Lines of Torres Vedras aimed at protecting Lisbon, the capital of Portugal, from French invasion.

[1][2] Following the Treaty of Fontainebleau signed between France and Spain in October 1807, which agreed on the invasion of Portugal, French troops under the command of General Junot entered the country, which requested support from the British.

This forced Junot to negotiate the Convention of Cintra, which led to the evacuation of the French army from Portugal.

In March 1809, Marshal Soult led a new French expedition that advanced south to the city of Porto before being repulsed by Portuguese-British troops and forced to withdraw.

The Lines of Torres Vedras, consisting of 152 forts, redoubts and other military installations, were built rapidly and in conditions of great secrecy, under the overall supervision of Colonel Richard Fletcher who was commander of the Royal Engineers.