How did Arthur Wellesley defend Portugal against the French army?

Arthur Wellesley, 1st Duke of Wellington, defended Portugal against French forces during the Peninsular War through a combination of tactical battlefield victories, strategic retreats, and the implementation of a scorched-earth policy.12

Key defensive measures included:

• Initial Campaigns: Upon landing in Portugal in 1808, Wellesley secured early victories at Roliça and Vimeiro, which forced the French to evacuate the country under the Convention of Sintra.13
• Strategic Fortification: Following his retreat to central Portugal in 1809, Wellesley secretly constructed the lines of Torres Vedras. These formidable defensive works protected the Lisbon peninsula and proved impenetrable to French forces.12
• Defensive Battles: Wellesley utilized the terrain to his advantage, notably defeating Marshal André Masséna at the Battle of Bussaco in 1810 before withdrawing behind his fortified lines.13
• Attrition: By maintaining a defensive posture and denying the French resources through scorched-earth tactics, Wellesley caused the French army to suffer significant privations, ultimately forcing their permanent evacuation of Portugal by the spring of 1811.13