Alongside the Spanish army in the campaign against Napoleon (1808-1814) was an assortment of freebooters, local peasants, and bandits who were organized into ad hoc regional private armies. These "guerrillas"--a term introduced to the English language during the Peninsular War--ambushed French convoys, attacked French encampments, and pounced upon, dodged, and fought French columns, often with extreme brutality. This book investigates for the first time the irregular Spanish forces and their role in resisting Napoleon. Delving deeply into previously untapped archival resources, Charles Esdaile arrives at an entirely new view of the Spanish guerrillas. He shows that the Spanish war against Napoleon was something other than the great popular crusade of legend, that many guerrillas were not armed civilians acting spontaneously, and that guerrillas were more often driven by personal motives than high-minded ideology. Tracking down the bandit armies and assessing their contributions, Esdaile offers important insights into the famous "little war" and the motives of those who fought it.