The Fort of São Vicente is located in the town and municipality of Torres Vedras, in the Lisbon District of Portugal. In 1809 it was the first of 152 forts, redoubts and other defences to be developed as part of three defensive lines between the Atlantic Ocean and the River Tagus that were designed by the Duke of Wellington to protect the Portuguese capital, Lisbon, from possible invasion by French troops during the Peninsular War. These came to be known as the Lines of Torres Vedras. Together with the Fort of Alqueidão, it is considered the most important fortress of those constructed for the Lines.