[2][3] Benito de San Juan started his military career as a Lieutenant Colonel of the hussars of Estremadura during the War of the Oranges (1801).
During the Peninsular War, he assumed command over some 12,000 troops,[4] defending the passes of Guadarrama, Fonfría, Navacerrada and Somosierra in the mountain range to the north of Madrid.
San Juan himself was wounded several times during the charge of the Polish cavalry and was forced to escape to Segovia,[4] allowing Napoleon to pass and establish his field headquarters at Buytrago.
[3] San Juan finally managed to withdraw with the remnants of his routed forces to Talavera de la Reina, where he attempted to rally his troops.
However, the demoralisation of the Spanish army, composed in a large part of untrained conscripts and peasant volunteers, led to a mutiny.