The Battle of Busaco
27 September 1810 · The Reverse-Slope Defence
The Battle of Busaco, fought on 27 September 1810, saw Wellington's reverse-slope defence work precisely as intended against Marshal Masséna's third French invasion of Portugal. French columns attacking uphill suffered severe casualties, after which Wellington withdrew as planned behind the Lines of Torres Vedras.
Background
Marshal Masséna's third French invasion of Portugal advanced into the interior. Wellington chose the long ridge at Busaco as a defensive position, hoping to bloody the French before withdrawing behind the Lines of Torres Vedras.
The Battle
French columns attacked uphill against carefully placed British and Portuguese divisions. The reverse-slope defence, which would become Wellington's signature tactic, worked precisely as intended. French casualties were severe; Allied casualties were comparatively light.
Significance
Busaco delayed Masséna's advance and demonstrated the growing skill of Wellington's Portuguese troops fighting alongside British regiments. Wellington then withdrew as planned behind the Lines of Torres Vedras, where the French army starved through the winter of 1810-1811.
Where This Fits in the Peninsular War
The Battle of Busaco was fought during the middle years of the war (1810-1811). See where it sits in the full chronology of the campaign, from the first British landings in Portugal to the final battle at Toulouse, on the complete campaign guide.
Page last updated: July 2026