In 1807, Napoleon was at the apex of his power and influence. Needing a fleet to blockade England, he conquered Portugal, with help from a small Spanish Army. He then betrayed the Spanish monarch and invaded Spain. Madrid and other cities throughout the Peninsula rose up against the French; in response, Napoleon sent troops to rapidly subdue them. Unexpectedly, the French Army was defeated at Baylen. Napoleon responded by personally leading some 300,000 troops; the Spanish Army’s defeat was accomplished quickly, and Spain seemed to be his. Yet four years later, the great French Army left Spain, exhausted, totally demoralized, and without food, basic clothing or supplies: a totally defeated force.
This paper maintains that this occurred because of the insurrection of the entire nation, and in particular the formation of a fierce and indomitable unconventional army: the Guerrilla. Encouraged and supported by the people, the Guerrilla gave the struggle the character of People in Arms: “Guerrilla” came to represent the spirit of rebellion that undermined the foundations of the Napoleonic Empire.
The guerrillas forced the French troops on the Peninsula into a dilemma that they never resolved: How to fight against regular armies, while simultaneously fighting against guerrilla operations that constantly threatened their rear, and the lines of communication and supply, thus forcing the deployment of more troops throughout the conquered territories. Napoleon never seemed able to grasp the danger of the insurrection and the guerrilla. This miscalculation was the leading cause of the downfall of his Empire.