How a 'Spanish Ulcer' helped unravel Napoleon's empire
Napoleon Bonaparte was considered invincible, until the Iberian Peninsula fought back. Through a brutal combination of formal battles and relentless guerrilla raids, a coalition of Spanish, Portuguese, and British forces turned a strategic occupation into a draining, bloody conflict that Napoleon himself famously called his 'Spanish ulcer'.
The conflict began not with a direct invasion of Spain, but as a maneuver to control Portugal. Following the 1807 Treaty of Tilsit, Napoleon sought to enforce his Continental System by closing European ports to British trade. When the Portuguese refused to abandon their long-standing alliance with Britain, French forces under General Junot marched through Spain to occupy Lisbon in late 1807. This occupation quickly escalated when Napoleon forced the abdications of the Spanish monarchs, Charles IV and Ferdinand VII, replacing them with his brother, Joseph Bonaparte.
What followed was a multifaceted war of resistance. While the British army, led by Arthur Wellesley—the future Duke of Serlington—landed in Portugal in August 1808 to support the peninsula, the Spanish response was more decentralized. The emergence of 'guerrilla' warfare, or 'little war,' saw Spanish partisans using ambushes and raids to harass French supply lines and isolate units. This constant pressure forced the French to commit massive numbers of troops to garrisoning hostile territory, effectively tying down the resources Napoleon desperately needed elsewhere.
The war also saw significant conventional milestones. The Battle of Bailén in 1808 provided a massive psychological boost to the resistance, marking the first time a Napoleonic field army was defeated in an open battle on the European continent. By 1812, the tide turned decisively as the French were weakened by the disastrous invasion of Russia. Allied forces achieved major victories at Salamanca and Vitoria, eventually pushing the exhausted French forces back across the Pyrenees by 1814. Though the war left Iberia in economic and social ruin, it proved that the French imperial machine could be broken.
Source: Peninsular War
