Guerrilla warfare in the Peninsular War

Guerrilla warfare in the Peninsular War refers to the armed civilian actions carried out by non-regular troops against Napoleon's French Imperial Army in Spain and Portugal during the Peninsular War. These armed men were a constant source of drain and harassment to the French army, as described by a Prussian officer fighting for the French: "Wherever we arrived, they disappeared, whenever we left, they arrived — they were everywhere and nowhere, they had no tangible center which could be attacked." The Peninsular War was significant in that it was the first to see a large-scale use of guerrilla warfare in European history and, partly as a result of the guerrillas, Napoleon's troops were not only defeated in the Peninsular War, but tied down on the Iberian Peninsula, unable to conduct military operations elsewhere on the European Continent.

Source: Wikipedia — Guerrilla warfare in the Peninsular War (CC BY-SA 4.0)