The Iberian Powder Keg: Origins of Conflict

The early 19th century witnessed a dramatic shift in European power dynamics as Napoleon Bonaparte sought to enforce his Continental System, an economic blockade designed to cripple Britain. Portugal, bound by centuries-old alliances with Britain, refused to comply, prompting Napoleon to orchestrate its invasion in October 1807. With Spanish cooperation secured through the Treaty of Fontainebleau, French troops swiftly occupied Portugal with minimal resistance.

Simultaneously, Spain descended into political chaos. King Carlos IV and his heir, Ferdinand, were locked in a bitter power struggle exacerbated by the unpopular Prime Minister Manuel Godoy. Public outrage erupted in March 1808 when rumors spread of Godoy’s plot to kidnap Ferdinand, triggering the Aranjuez Mutiny. Napoleon seized this moment of instability, summoning both Spanish monarchs to Bayonne in May 1808 and forcing their abdications. In their place, he installed his brother Joseph Bonaparte as King of Spain—a move that would ignite widespread rebellion.

The Spanish Uprising and Guerrilla Warfare

The overthrow of the Bourbon monarchy sparked a national uprising. Beginning in Madrid on May 2, 1808 (immortalized in Goya’s The Third of May 1808), the revolt spread rapidly. Regional juntas, particularly in Asturias, organized resistance under the banner of guerrilla warfare—a term now synonymous with irregular combat. The Catholic Church played a pivotal role, framing the conflict as a holy war against Napoleon’s “godless” regime.

French forces, though superior in conventional battles, struggled against the relentless guerrilla tactics. The brutality of this conflict, marked by atrocities on both sides, was captured vividly in Goya’s Disasters of War series. By December 1808, Napoleon reclaimed Madrid, but Joseph Bonaparte’s authority remained confined to French-occupied zones. His government’s reforms—such as abolishing primogeniture and secularizing Church lands—won limited support among liberal afrancesados but alienated the majority of Spaniards.

British Intervention and the Tide Turns

The war’s turning point came with British involvement. Under General Arthur Wellesley (later the Duke of Wellington), Anglo-Portuguese forces scored decisive victories, including at Talavera (1809) and the liberation of Portugal by 1811. Meanwhile, Spanish resistance persisted. The Cortes of Cádiz, a provisional government operating under British naval protection, drafted the groundbreaking 1812 Constitution—a progressive document declaring popular sovereignty and limited monarchy, though it retained Catholicism as the state religion.

Despite its short lifespan (abolished by Ferdinand VII in 1814), the Cádiz Constitution became a symbol for liberals across Europe, inspiring future revolutions. Its legacy endured in Latin America, where creole elites adopted its principles during independence movements.

The Wider European Impact

Napoleon’s Iberian quagmire had unintended consequences. Austria, emboldened by French setbacks, launched the War of the Fifth Coalition in 1809. Though defeated at Wagram, Austria’s reforms—including a militia system inspired by Spanish guerrillas—highlighted the vulnerability of Napoleonic hegemony.

Meanwhile, Napoleon’s dynastic ambitions led to his marriage with Marie Louise of Austria in 1810, a union meant to legitimize his empire. Yet his annexation of papal territories and enforcement of the Continental System alienated key allies, including Russia. Tsar Alexander I’s defiance—coupled with economic warfare—set the stage for the disastrous 1812 invasion.

The Road to Moscow and Collapse

Napoleon’s invasion of Russia in June 1812 marked the beginning of his downfall. Despite capturing Moscow, his army was decimated by winter, guerrilla attacks, and Kutuzov’s scorched-earth tactics. The retreat from Russia shattered the myth of Napoleonic invincibility, emboldening Prussia, Sweden, and Austria to join the Sixth Coalition in 1813.

Legacy: The Birth of Modern Warfare and Nationalism

The Peninsular War redefined European conflict. Guerrilla tactics, popular mobilization, and nationalist fervor foreshadowed modern warfare. Spain’s resistance became a rallying cry for anti-Napoleonic movements, while the Cádiz Constitution influenced liberal revolutions into the 1820s.

For Napoleon, the Iberian campaign was a costly distraction that drained resources and morale. Combined with the Russian disaster, it sealed his fate—culminating in abdication in 1814. Yet the war’s cultural impact endured, from Goya’s haunting artworks to the enduring Spanish myth of la guerrilla heroica.

In the end, the Peninsular War was more than a military campaign; it was a crucible that forged modern notions of sovereignty, resistance, and the limits of imperial power.