Interestingly, Napier in volume four hints at guerrilha activity in Portugal 1810-1811 but, in my opinion, most probably due to prejudice, comes to an incorrect conclusion reporting there were “so many complaints of the cruelty committed by Massena’s army while at Santarem, that Lord Wellington had some thoughts of reprisals; but having first caused strict enquiry to be made, it was discovered that in most cases, the ordencança, after having submitted to the French, took advantage of it to destroy the stragglers and small detachments, and the cruelty complained of was only the infliction of legitimate punishment for such conduct”

Napier, History, vol IV, p. 175 (Constable Re-print, 1993)