Peninsular_War The Peninsular War was a contest between France and the allied powers of Spain, the United Kingdom, and Portugal for control of the Iberian Peninsula during the Napoleonic Wars. The war began when French armies invaded Portugal in 1807 and Spain in 1808 and lasted until the Sixth Coalition defeated Napoleon in 1814.Spain's liberation struggle marked one of the first national wars and the emergence of large-scale guerrillas, from which the English language borrowed the word.