At the beginning of the Peninsular War French Napoleonic troops under the command of General Jean-Andoche Junot reached the limits of Lisbon on November 30, 1807. The fort was transformed into barracks for the French occupation troops under the command of General Jean-Pierre Travot, while the bar of the Tagus River was blocked by the British navy in support of the Portuguese. The fort passed into British hands following the Sintra Convention, on 2 September 1808. In 1809 it was earmarked as the evacuation point for British troops under the command of Arthur Wellesley, 1st Duke of Wellington in the event that British and Portuguese troops were unable to repel a further French invasion. The fort was protected by a series of military works constructed under Wellington's orders and collectively known as the third line of the Lines of Torres Vedras. In 1831, during the Portuguese Civil War (1828-1834), it was the target of artillery fire from the French fleet under the command of Admiral Albin Roussin.