Napoleon's Continental System, his attempt to strangle British trade by closing every European port to it, needed Spain and Portugal to comply. When Portugal refused, the Emperor sent his armies across the Pyrenees, and this film follows what became one of the longest and bloodiest campaigns of the Napoleonic Wars. Historians walk through the string of decisions that turned a quick occupation into a six-year quagmire: the Spanish uprising against French rule, the guerrilla tactics that gave the war its name, and Wellington's slow campaign to push the French back toward the border. Battlefields at Talavera, Badajoz, and Vitoria get detailed treatment, with maps and location filming used to show how terrain and supply lines shaped each engagement. The film sets the war inside Napoleon's larger strategic picture, arguing that Spain became the drain that weakened his grip on the rest of Europe well before Russia did. Expert interviews carry the analysis throughout, backed by period art and paintings rather than reenactment footage.