The Peninsular War took place from 1808 to 1814 on the Iberian Peninsula. It began when Napoleon invaded Spain and Portugal. Widespread resistance from Spanish and Portuguese forces, along with guerrilla warfare, led to a protracted conflict. The war significantly weakened Napoleon's forces and contributed to his strategic challenges. The conflict ended with the defeat of French forces in the region by the Sixth Coalition, consisting of British, Spanish, and Portuguese allies.