CASUALTY RECORD // June 18, 1813
Battle of San Millan-Osma
Estimated casualties — killed, wounded, captured, and missing — by side, with confidence labels per surviving record.
Casualties by side
2 sides catalogued · combined 220–500 estimated
Empire français
120–400
Medium-confidence figure
Royaume-Uni de Grande-Bretagne et d'Irlande
100
Medium-confidence figure
Battle context
The Battles of San Millán and Osma on 18 June 1813 formed part of Wellington's broader 1813 campaign in northeast Spain, a drive that brought two Allied divisions into sharp contact with two divisions of King Joseph Bonaparte's French army. The engagements proved costly to the French: the fight at San Millán was described as extremely punishing to Maucune's division, and a subsequent French attempt to hold a defensive position at Osma the same day was beaten back with little difficulty. Together the two actions degraded French cohesion at a critical moment in the campaign, stripping Joseph's army of the ability to anchor a line in the region and contributing to the unraveling of French operational control in northern Spain ahead of the decisive confrontation that followed.
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