 Despite his victory over elements of Marshal André Masséna's Army of Portugal at the Battle of Bussaco in September 1810, Viscount Wellington was forced by Masséna's subsequent maneuvering to withdraw his numerically inferior force behind the extensive series of fortifications he had prepared around Torres Vedras to protect the approaches to Lisbon. By 10 October 1810 only the British light division and some cavalry patrols remained outside the "Lines". Wellington manned the fortifications with "secondary troops" — 25,000 Portuguese militia, 8,000 Spaniards and 2,500 British marines and artillerymen — keeping his main field army of British and Portuguese regulars dispersed in order to rapidly meet a French assault on any point of the Lines.
