Auxiliary Legion The Auxiliary Legion , also called the British Legion ( " La Legión Británica " ) , existed from 1835 to 1837 . It was a British military force sent to Spain to support the Liberals and Queen Isabella II of Spain against the Carlists in the First Carlist War . History . Under the Quadruple Alliance , Great Britain had controlled maritime traffic along the Cantabrian coast since the beginning of the war . In 1835 the war was not going well for the Liberal side and they asked their allies to become more involved in the war . The French sent their Foreign Legion which landed at Tarragona on 17 August with around 4 , 000 men and was renamed the Spanish Legion . Although the British refused to send troops directly , in June 1835 , they decided to form a military volunteer corps , and that became designated an auxiliary to the Spanish Legion . By the end of the summer of 1836 a force of 10 , 000 men under the command of De Lacy Evans had assembled in San Sebastian . They fought near Hernani and Vitoria , but were pushed back and had to hold the fort on Mount Urgul de San Sebastián , to prevent the Carlists from taking the city . In November 1836 they were put under the command of Baldomero Espartero and helped to lift the siege of Bilbao . In 1837 they suffered a serious defeat in the Battle of Oriamendi , but were successful in stopping the " Expedición Real " , an attempt by the Carlists to march on Madrid . The volunteers had signed on for a tour of two years and by the end of 1837 most of the men had returned home . Some 1 , 000 – 1 , 500 men remained , and fought on several fronts . Their casualties were so heavy that in practical terms the unit was dissolved . In total a quarter of the force – some 2 , 500 men – died , only half of them in combat . Their presence had not been well received by the Carlists ; one former soldier wrote that " to our foes , we of the British Legion were the most odious of all ; strangers , mercenaries , heretics , scoffers , polluters of their sacred soil ; so they did term us . For us there was no quarter ; in the heat of battle , or by cold judicial form , it was all the same : to fall into their hands was certainly a tortured death . " Organization . It would appear that most of the 9 , 600 men forming the Legion were volunteers from British Army line regiments . The only " regular " troops who served in the war were men of the Royal Navy , Royal Marines , Royal Artillery , and Royal Engineers . Recruiting and training began in 1835 . The Legion was to comprise 8 , 500 infantry ( in 10 battalions ) , 550 rifles , 700 cavalry and 300 artillery . Units . British regulars attached to the Legion . On occasion some regular British troops were attached to the Legion , including : The first British Marines under Lord John Hay ( the British Commodore ) landed to garrison Portugalete in Apr 1836 . In May the Royal Marines were expanded to a full battalion under Major Owen . Small detachments of Royal Marine Artillery , Royal Artillery and Royal Engineers were subsequently added . In November 1836 , 39 officers and men of the British Royal Artillery joined the Naval force supporting the British Auxiliary Legion . 60 additional men arrived in Jan 1837 . There were also 100 men of the Royal Marine Artillery . Cairns says all British Artillery used 9 - pounder smoothbore field pieces and 5 1 / 2 ” howitzers , along with a few Congreve rocket launchers and light mountain pieces . Somerville ( 1995 ) , however , gives the British Auxiliary Legion 6 - pounders and short 12 - pounders ( presumably howitzers ) and the Royal Artillery larger pieces including large howitzers . Legion artillery organisation : British Royal and Marine Artillery : British Auxiliary Legion Artillery Spanish artillery :