In 1808, during the Peninsular War fought by Spain against invaders from France, the Battle of Somosierra took place at the range's Somosierra Pass, where the Spanish were defeated by Napoleonic troops composed principally of Polish lancers. Likewise, in the Battle of Guadarrama during the Spanish Civil War (1936-1939) the range comprised an important front with skirmishes fought in the mountain passes between the loyalist and the rebel faction. Today, trenches and gun emplacements still survive along the line of the mountains' summits.