The battle of Cabezon, 12 June 1808, was a crushing French victory won against an inexperienced Spanish army under the command of captain-general Don Gregorio de la Cuesta. The French forces in north eastern Spain, some 25,000 strong, were under the command of Marshal Bessières. On learning of a revolt in Santander, he dispatched General Merle and 5,000 men to put down the revolt. However, before Merle could reach Santander news reached Bessières of a more serious threat. General Cuesta had raised an army at Valladolid, with which he could threaten French communications between Madrid and Burgos. Bessières responded by recalling Merle and sending out another column under General Lasalle.
Cuesta’s force, rather grandly called the “Army of Castile”, contained 4,000-5,000 raw recruits, with no more than two weeks training, and 300 regular cavalry. What his infantry lacked in experience they made up for in enthusiasm, putting Cuesta under pressure to seek a battle. This army moved to the bridge of Cabezon, where the road from Burgos to Valladolid crossed the river Pisuerga.
General Lasalle soon discovered the Spanish position. His own force was smaller than the Spanish army, but on 11 June he was joined by Merle, giving him a total of 9,000 men.
Cuesta made the French general’s job a lot easier. Instead of destroying the bridge and defending the far bank of the river against the French, he took his men across the bridge and lined them up on the far side. On 12 June Lasalle took advantage of this extraordinary discussion, and launched a devastating attack on the Spanish position, which almost immediately collapsed. The fleeing Spanish were now trapped between the French and the river, with only one bridge to escape across. Casualties were high – hundreds were either killed by the French or drowned in the river. Cuesta himself, with the survivors, fled west to Medina de Rio Seco. The French suffered 12 dead and 30 wounded and in the aftermath of the battle were able to occupy Valladolid without a fight. Merle was able to return to his original task, occupying Santander on 23 June.