The battle of the Somosierra Pass, 30 November 1808, was the final Spanish attempt to stop Napoleon reaching Madrid during his 1808 campaign in Spain. At the start of that campaign the Spanish armies had been on the Ebro, but defeats at Gamonel on 10 November and Tudela on 23 November had left Napoleon free to march on Madrid. The Junta at Madrid had 21,000 men at their disposal, while Napoleon was advancing at the head of an advance guard 45,000 strong, with another 95,000 following close behind! To make things worse, the Junta refused to believe both that Napoleon had more than 80,000 men in Spain, and that he could be about to make a serious attack on Madrid.
The only barrier between Napoleon and Madrid was the Sierra de Guadarrama mountain range. This was crossed by two main passes, at Somosierra and at Guadarrama. The Spanish had to split their small army between these two passes. They chose to post 9,000 men at the Guadarrama, while the larger force, 12,000 men under General San Juan, was sent to the Somosierra.
San Juan had nowhere enough men to defend this pass. The plateau at the head of the pass was overlooked by flanking heights that were perfectly accessible to infantry, and which San Juan would have had to hold in force if he was to successfully delay Napoleon. Instead, he split his army in two. 3,000 men were posted at the town of Sepulveda, just off the main road at the northern foot of the hills, where they would be unable to play any part in the defence of the pass. The remaining 9,000 men were concentrated at the top of the pass, with his small artillery detachment of sixteen guns spread out across the top of the rise, protected by an earthwork. Some of the infantry were posted on the slopes on either side of the pass, but no effort was made to entrench or to otherwise improve their positions.
Napoleon began to climb the pass on the morning of 30 November. The French reached San Juan’s position late in the morning. Napoleon began his attack sensibly enough, ordering Ruffin’s division to clear the pass. Four battalions made their way up the road, while three battalions advanced up the slopes on either side of the pass. Fighting soon broke out on the hillside, and the French were making slow but steady progress towards the ridgeline, at which point the Spanish artillery would have been forced to retreat.
At this point Napoleon seems to have become bored with the slow progress, or decided that he wanted a more dramatic victory. His cavalry escort for the day was made up of a squadron of Polish Light Horse, 87 strong. Napoleon turned to them, and ordered them to charge the Spanish guns. He appears to have been motivated by a real contempt for the Spanish soldiers, who he expected to turn and flee as the cavalry approached. The result was a massacre. The cavalry could only approach along the road, where they were exposed to the fire of all sixteen Spanish guns. Of the 88 men who began the charge, 44 were killed and twelve wounded. Amongst the dead was Napoleon’s aide-de-camp, Philippe de Ségur, who had been sent forward when the Poles briefly took cover.
Soon after this Ruffin’s infantry reached the ridge, and the Spanish began to waver. This was the right time for a cavalry charge, and when Napoleon sent in the rest of the Polish Light Cavalry and part of the guard cavalry, the Spanish were finally forced to abandon their guns and retreat. Sometimes presented as a cavalry victory (partly because Napoleon’s own report on the battle ignored the destruction of his escort and gave the credit to the victory to the Poles), the bulk of the fighting was carried out by Ruffin’s ten battalions of infantry, who defeated a force of fifteen battalions.
Napoleon was now free to advance on Madrid. He reached the base of the pass on the evening of 30 November, and the French advance guard reached Madrid on 1 December and after a short period of resistance, entered the city on 4 December.