In the autumn of 1810, the French forces of Marshal Masséna are invading Portugal and are temporarily halted by the Anglo-Portuguese army under Viscount Wellington at the Battle of Bussaco. As a bitter winter approaches, Wellington withdraws his troops towards the fortifications he has prepared in secret at the Lines of Torres Vedras. Using a scorched earth defence, he forces the inhabitants to evacuate the land in front of the Lines and destroys all supplies which could be useful to the French. The film illustrates these dramatic events by a series of vignettes which show the effects on combatants, both regular soldiers and guerrillas, and on the civilian population.