The Lines of Torres Vedras were lines of forts and other military defences built in secrecy to defend Lisbon during the Peninsular War. Named after the nearby town of Torres Vedras, they were ordered by Arthur Wellesley, Viscount Wellington, constructed by Colonel Richard Fletcher and his Portuguese workers between November 1809 and September 1810, and used to stop Marshal Masséna's 1810 offensive. The Lines were declared a National Heritage by the Portuguese Government in March 2019.
Development At the beginning of the Peninsular War (1807–14) France and Spain signed the Treaty of Fontainebleau in October 1807. This provided for the invasion and subsequent division of Portuguese territory into three kingdoms. Subsequently, French troops under the command of General Junot entered Portugal, which requested support from the British. In July 1808 troops commanded by Sir Arthur Wellesley, the later Duke of Wellington, landed in Portugal and defeated French troops at the Battles of Roliça and Vimeiro. 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. After this retreat, Wellesley's forces advanced into Spain to join 33,000 Spanish troops under General Cuesta. At Talavera, some 120 kilometres (75 mi) southwest of Madrid, they encountered and defeated 46,000 French soldiers under Marshal Claude Victor. After the Battle of Talavera, Wellington realised that he was seriously outnumbered by the French army, giving rise to the possibility that he could be forced to retreat to Portugal and possibly evacuate. He decided to strengthen the proposed evacuation area around the Fort of São Julião da Barra on the estuary of the River Tagus, near Lisbon.
Planning
In October 1809, Wellington, drawing on topographical maps prepared by José Maria das Neves Costa, and making use of a report that was prepared for General Junot in 1807, surveyed the area north of Lisbon with Lieutenant-Colonel Richard Fletcher. Eventually they chose the terrain from Torres Vedras to Lisbon because of its mountainous characteristics. From north to south, great undulations created peaks that straddled deep valleys, great gullies and wide ravines. The rugged and inhospitable area offered numerous possibilities for a stubborn rearguard fight from forts on many of the peaks. Following the decision on the location, Lieutenant-Colonel Richard Fletcher ordered the work to begin on a network of interlocking fortifications, redoubts, escarpments, dams that flooded large areas, and other defences. Roads were also built to enable troops to move rapidly between forts. The work was supervised by Fletcher, assisted by Major John Thomas Jones, and 11 other British Officers, four Portuguese Army Engineers, and two KGL officers. The cost was less than £200,000 (equivalent to £13,579,000 in 2025) according to the Royal Engineers, one of the least expensive but most productive military investments in history. When the results of the surveys by the Royal Engineers were completed, it was possible, in February 1810, to begin work on 150 smaller interlinking defensive positions, using, wherever possible, the natural features of the landscape. The work was accelerated after the loss to the French of the fortress at the Siege of Almeida in August 1810, which prompted the public conscription of Portuguese labourers to work on the lines. The works were sufficiently complete to halt the advance of the French troops, who arrived in October of the same year. Even after the French had retreated from Portugal, construction of the lines continued in expectation of their return, and in 1812 34,000 men were still working on them. On completion there were 152 fortifications with a total of 648 cannon.
Construction
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