Guerrilla warfare in the Peninsular War

"[3] While folklore would often elevate the status of local heroes, many of the leading guerrilleros were actually regular army officers commanding irregular "troops".

Apart from the odd setback, such as General Castaños' surprise victory at Bailén, in part due to guerrilla warfare between Madrid and Andalusia, and especially in the Sierra Morena, a victory which helped persuade the British government that Napoleon could be defeated, the French troops were largely undefeated on the open battlefield.

Spanish guerrillas frequently attacked Grand Armee rear echelon components, including communication and supply lines.

The success of these fighters in the conflict was owed to the few men and small amount of equipment and energy required to hold a large area and disrupt French movements.

"[10] By the end of 1809, the damage caused by the guerrillas led to the Dutch Brigade, under Major-General Chassé, being deployed, almost exclusively and, largely unsuccessfully, in counter-guerrilla warfare in La Mancha.