Battle of San Millan - Osma In the Battles of San Millán and Osma ( 18 June 1813 ) two divisions of the Allied army of Arthur Wellesley , Marquess of Wellington clashed with two divisions of King Joseph Bonaparte ' s Imperial French army in northeast Spain . At San Millán de San Zadornil , Charles Alten ' s Light Division mauled Antoine Louis Popon de Maucune ' s French division . At Osma , to the northeast , Jacques Thomas Sarrut ' s French division fought an inconclusive skirmish with Kenneth Howard ' s division before withdrawing to the southeast . San Millán de San Zadornil is located in the Province of Burgos while Osma is in Álava , Basque Country . The actions occurred during the Peninsular War , part of the wider Napoleonic Wars . In the summer of 1813 , Wellington ' s army thrust into Spain from Portugal with a powerful army composed of British , Portuguese , and Spanish soldiers . The British general outmaneuvered his opponents and forced the French to abandon Salamanca , Valladolid , Madrid , and Burgos . King Joseph and Marshal Jean - Baptiste Jourdan believed their position behind the Ebro River was secure , but Wellington sent his troops marching to outflank the line on the north . As Sarrut moved north , his troops bumped into Howard ' s soldiers . Maucune ' s division at San Millán was suddenly attacked from the west by Alten . Believing Maucune ' s division was no longer fit for combat , Joseph used it to escort a convoy and it missed the decisive Battle of Vitoria three days later . Background . After the campaign in the fall of 1812 , Arthur Wellesley , Marquess of Wellington ' s army was in poor shape , with 18 , 000 soldiers on the sick list . On the other hand , the campaign resulted in the capture of the cities of Ciudad Rodrigo , Badajoz , Astorga , and Seville , and the provinces of Andalusia , Asturias , and Extremadura . Also , 5 , 000 new replacements came out from Great Britain . The winter of 1812 also witnessed the destruction of Emperor Napoleon ' s army during the French invasion of Russia . In order to rebuild his army in Germany , Napoleon demanded reinforcements of 15 , 000 men from King Joseph Bonaparte ' s army and 5 , 000 men from Marshal Louis Gabriel Suchet ' s army in eastern Spain . To Joseph ' s relief , Marshal Nicolas Soult was also recalled to join Napoleon and was replaced by Marshal Jean - Baptiste Jourdan . The various withdrawals left Joseph in control of 95 , 000 troops in three armies . These were the 42 , 000 - man Army of Portugal under Honoré Charles Reille , the 36 , 000 - strong Army of the South led by Honoré Théodore Maxime Gazan de la Peyrière and the 17 , 000 - man Army of the Center directed by Jean - Baptiste Drouet , Comte d ' Erlon . Meanwhile , Joseph ' s forces reimposed control over northern and central Spain . However , guerilla warfare in northern Spain soon spiralled out of control and Napoleon ordered Bertrand Clausel to replace Marie - Francois Auguste de Caffarelli du Falga as commander of the Army of the North . Obsessed with the Spanish partisans ' disruption of communications with France , the emperor ordered the Army of Portugal ' s six divisions be made available to Clausel for anti - guerilla operations . With heavy reinforcements from the Army of Portugal , Clausel set about trying to suppress the Navarrese partisans . On 30 March 1813 , the French general suffered a setback when guerilla chief Francisco Espoz y Mina ambushed a French column . While two battalions were busily plundering Lerín , Mina surprised them with 2 , 100 guerillas , including 200 lancers . Out of 1 , 500 French soldiers , only a handful escaped the disaster and 663 were made prisoner . Marie Étienne de Barbot , commander of the 2nd Division of the Army of Portugal , was nearby with six battalions but failed to succor his ambushed column . On 12 May 1813 , Clausel found and destroyed Mina ' s encampment in the Roncal Valley , inflicting 1 , 000 casualties on the guerillas . On the same day , Maximilien Sebastien Foy recaptured Castro Urdiales on the Bay of Biscay . Foy commanded his own 1st Division and Jacques Thomas Sarrut ' s 4th Division , both of the Army of Portugal , and Giuseppe Federico Palombini ' s Italian Division from the Army of the Center . The Franco - Italians lost 150 killed and wounded out of 10 , 000 men and 18 siege guns . Colonel Pedro Alvarez ' s 1 , 000 Spanish soldiers suffered losses of 160 killed and wounded . Before being evacuated by the Royal Navy , Alvarez ' s men detonated the powder magazines and threw their cannons into the bay . While Clausel and Foy were employed hunting down guerillas , critical events were occurring elsewhere in Spain . Allied offensive . After the various subtractions of strength , Joseph had only 33 , 000 infantry , 9 , 000 cavalry , and 100 guns to face Wellington . Napoleon assured his brother Joseph that the British general was too cautious to take advantage of the situation , and in any case could only deploy 30 , 000 British and 20 , 000 Portuguese soldiers . In fact , Wellington was on the march with 52 , 000 British , 28 , 000 Portuguese , and 25 , 000 Spanish troops . The three - division right wing under Rowland Hill was ordered to advance northeast to Salamanca while the six - division left wing led by Thomas Graham crossed to the north bank of the Douro River inside Portugal . Joseph and Jourdan posted Gazan ' s Army of the South and d ' Erlon ' s Army of the Center to cover Valladolid and Segovia , while Reille with the remaining 17 , 000 troops from the Army of Portugal was sent to the north to help suppress guerillas . At this time , Clausel ' s 20 , 000 soldiers were located near Pamplona , far to the east . Hill ' s wing seized Salamanca on 26 May 1813 , chasing Eugene - Casimir Villatte ' s French troops out of the city and capturing 200 French soldiers . Meanwhile , Graham ' s soldiers forded the flooding Esla River at Almendra on 31 May , losing some men to drowning and much equipment . Augustin Darricau , whose division held Zamora , had sent a cavalry reconnaissance to the west on 20 May that reported no enemy activity . The French horsemen just missed Graham , who crossed the Douro soon afterward . Finally alerted that 64 , 000 men were bearing down on Zamora from the northwest , Darricau bolted to the east , leaving Graham to occupy the town on the morning of 2 June . The same day , Colquhoun Grant ' s cavalry brigade consisting of the 10th , 15th , and 18th Hussar Regiments defeated a French cavalry force at Morales de Toro . The French mounted troops comprised the 16th and 21st Dragoon Regiments under Pierre Benoît Soult and their horses were in very bad condition . The 16th was virtually destroyed , with two officers and 308 troopers being made prisoners ; of these 100 were wounded . British casualties in the clash were only 16 killed and wounded . On 3 June , Hill ' s wing joined Graham on the north bank of the Douro at Toro . At this time , Wellington had 90 , 000 troops concentrated while the French could only count 51 , 000 men . Alarmed at the odds against them , Joseph and Jourdan sent a frantic message to Clausel asking for help and withdrew toward Burgos . Joseph and Jourdan expected Wellington to advance along the great road from Valladolid to Burgos . Instead , the British general directed Hill and the right wing to advance just to the north of the road . Graham and the left wing were farther to the north . To Graham ' s left marched a Spanish corps led by Pedro Agustín Girón with 12 , 000 men . The French fell back behind the Pisuerga River and then to Burgos but , to their bewilderment only a handful of Spanish cavalry directly pursued them . Wellington ' s great flank march continued and the French abandoned Burgos on 13 June , blowing up the castle that had been the focus of the Siege of Burgos the previous autumn . Unsuspected by the French , the British commander was prepared to change his base from Lisbon to Santander on the Bay of Biscay . During the French retreat , Reille turned up with three divisions of the Army of Portugal , adding 15 , 000 men to Joseph ' s army . Clausel ' s 25 , 000 troops were at large but Joseph had no idea where they were . For his part , Clausel never received any messages from the king until 15 June , at which time he gathered four divisions and set out to join the main army . Joseph massed his army behind the Ebro River , believing that it would be impossible for Wellington ' s army to outflank the line on the north . On 15 June , Hill ' s wing crossed the Ebro at Puente Arenas and Graham ' s wing crossed at San Martin de Lines . From the 13th until a cavalry encounter on 17 June , the French lost all contact with their adversaries . Osma . Joseph found out that Girón ' s column was menacing Bilbao so he directed Reille to move north with three divisions on 18 June . Reille soon ran afoul of Graham ' s wing of the Allied army . Graham had with him the 1st Division , 5th Division , George Anson ' s Light Dragoon Brigade , and Thomas Bradford ' s Independent Portuguese Brigade . On the 18th , Sarrut ' s 4th Division of the Army of Portugal blundered into Kenneth Howard ' s 1st Division at Osma . Sarrut ' s force included two battalions each of the 2nd Light , 4th Light , and 36th Line Infantry Regiments , about 3 , 800 men . The French encountered the 1st and 2nd Light King ' s German Legion ( KGL ) Battalions of Colin Halkett ' s brigade , about 1 , 200 troops . In the clash , the French suffered 120 killed and wounded while the KGL units lost between 50 and 60 casualties . Reille retreated south to link up with Joseph ' s army at Miranda de Ebro . Sarrut ' s division was organized into two brigades under Joseph François Fririon and Jean Baptiste Pierre Menne plus an artillery battery . It had a total strength of 146 officers and 4 , 656 rank and file . Fririon ' s brigade was made up of the 2nd Light and the 36th Line while Menne ' s brigade had the 4th Light and the 65th Line . Howard ' s division comprised the 1 , 728 - man 1st Brigade under Edward Stopford and the 3 , 126 - strong 2nd Brigade under Halkett . Stopford commanded one company of the 5th Battalion of the 60th Foot , and the 1st Battalions of the 2nd Foot Guards and the 3rd Foot Guards . Halkett ' s all - KGL brigade included the 1st Light , 2nd Light , 1st Line , 2nd Line , and 5th Line Battalions . San Millan . On 18 June 1813 , Antoine Louis Popon de Maucune ' s 5th Division of the Army of Portugal counted 4 , 800 men . The division included two battalions each of the 15th , 66th , 82nd , and 86th Line Infantry Regiments . That day , one of the brigades was halted at the village of San Millán de San Zadornil . The leading brigade of the Light Division under John Ormsby Vandeleur marched up from the west and attacked . As Vandeleur ' s men pushed the French from the village and east along the road , Maucune ' s second brigade appeared from a rocky gorge to the southwest . The second brigade was in the right rear of Vandeleur ' s brigade , but before the French could take advantage of the situation , James Kempt ' s brigade arrived on the scene . Kempt immediately attacked and , to avoid being taken in flank and rear , Maucune ' s second brigade left the road and began to retreat across the hillsides . Noticing what was going on behind him , Vandeleur pulled the 1st Battalion of the 52nd Foot out of line and turned it against the French second brigade . Under the pressure , Maucune ' s second brigade collapsed and the men ran away . The Light Division was commanded by Charles Alten and consisted of Kempt ' s 1st Brigade and Vandeleur ' s 2nd Brigade . The 2 , 597 - man 1st Brigade consisted of the 1st Battalion of the 43rd Foot , eight companies of the 1st Battalion of the 95th Rifles , five companies of the 3rd Battalion of the 95th Rifles , and the 3rd Portuguese Caçadores Battalion . The 2 , 887 - strong 2nd Brigade was made up of the 1st Battalion of the 52nd Foot , six companies of the 2nd Battalion of the 95th Rifles , the 17th Portuguese Line Infantry Regiment , and the 1st Portuguese Caçadores Battalion . The Light Division had 5 , 484 officers and men , of whom 1 , 945 were Portuguese . Maucune lost about 400 casualties . Of these , about 300 were captured along with the division ' s baggage train . British losses were about 100 killed and wounded . As the French soldiers fled , many threw away their knapsacks . The division reorganized at Miranda de Ebro . Joseph was furious with Maucune for allowing his division to be routed . The unit was so roughly handled that the king decided it was no longer fit for combat and assigned it to guard a convoy bound for France . The convoy set out from Vitoria at 2 : 00 AM on the morning of the 21st . The division would be sorely missed at the Battle of Vitoria later that day .