Durante nuestra Guerra de Independencia (1808-1814), que los británicos llamaron Peninsular War, los franceses fueron hostigados en campo abierto por partidas de irregulares. Era la única forma que los españoles encontraron de enfrentarse a los invasores. Desde 1809, comenzó a utilizarse en inglés la palabra guerrilla (a veces escrita guerilla) en el mismo sentido que tiene en castellano.
The guerillas
After the defeats of their armies, numbers of fugitives took to the hills, threw away their uniforms, obtained peasants' dresses, and set up as what they called guerillas, which is only another term for bandits; for although their efforts are chiefly directed against us, they do not hesitate to plunder their own people, when they need provisions, and are a perfect scourge to all the villages among the hills between the Bay of Biscay and the Mediterranean. Of course, they are strongest along the line of communication with France; but it may be said that, roughly, where there are mountains there are guerillas, though there are but few of them along the hills we crossed between the valley of the Tagus and that of the Douro.
G. A. HENTY, Under Wellington's Command. A Tale of the Peninsular War.
