The combat of San Munoz (17 November 1812) was a rearguard action towards the end of Wellington's retreat from Burgos back to Portugal.
By 10 November Wellington's army was back in its strong positions north of Salamanca, facing the united French forces of Suchet, Soult and King Joseph. On 10-11 November the French were repulsed at Alba de Tormes, and decided to cross the river further to the south. They crossed early on 15 November, and the two armies were soon facinn each other over the Salamanca battlefield. Wellington was finally forced to order a retreat back towards Ciudad Rodrigo early in the afternoon when it became clear that the French weren’t going to make the mistake of allowing their army to get stretched out for a second time.
The British retreated in three columns. The Light Division formed the rearguard of the middle column, which was the only one that was closely pressed by Soult. At first it the only French troops were the cavalry, although they did capture General Paget. In the late afternoon the column reached the Heubra River at San Munoz. The column began to cross the river, ready to camp on the far bank. For once the French actually had some infantry close by, and just before the Light Division began to cross Daricau's division appeared on the scene.
The Light Division thus had to cross the river while being attacked from the rear. Three companies from the 43rd and one from the 95th formed a rear guard and held off Daricau's skirmishers while the main body of the division crossed the river. They then managed to escape across the river while being closely pursed by the French.
Soult then paused to bring up his artillery and soon opened fire on the Light and 7th Division, but the wet weather and soft ground reduced the impact of his shells. This bombardment only caused 30 casualties in the 7th Division, and at the end of the day Soult abandoned any plans to attack across the river.
Daricau's division lost 226 men during the fighting at San Munoz. The British lost 365 men, but only 187 of these were combat casualties - the rest were prisoners taken during the retreat.
On the following morning the British expected the French to attack, but Soult had no intention of attacking Wellington in a strong position after crossing a river. Instead he waited for the British to resume their retreat, and then sent a small cavalry force to watch the retreat. On 19 November Soult ordered his men to retreat east, ending the campaign.