Siege of Cádiz The Siege of Cádiz was a siege of the large Spanish naval base of Cádiz by a French army from February 5 , 1810 to August 24 , 1812 during the Peninsular War . Following the occupation of Seville , Cádiz became the Spanish seat of power , and was targeted by 70 , 000 French troops under the command of the Marshals Claude Victor and Nicolas Jean de Dieu Soult for one of the most important sieges of the war . Defending the city were 2 , 000 Spanish troops who , as the siege progressed , received aid from 10 , 000 Spanish reinforcements as well as British and Portuguese troops . During the siege , which lasted two and a half years , the Cortes Generales government in Cadiz ( the Cádiz Cortes ) drew up a new constitution to reduce the strength of the monarchy ( a constitution eventually revoked by Fernando VII ) . In October 1810 , a mixed Anglo - Spanish relief force embarked on a disastrous landing at Fuengirola . A second relief attempt was made at Tarifa in 1811 . However , despite defeating a detached French force of 15 , 000 – 20 , 000 under Marshal Victor at the Battle of Barrosa , the siege was not lifted . In 1812 , the Battle of Salamanca eventually forced the French troops to retreat from Andalusia , for fear of being cut off by the allied armies . Defeat at Cádiz contributed decisively to the liberation of Spain from French occupation , due to the survival of the Spanish government and the use of Cádiz as a jump off point for the Allied forces . Prelude to the battle . In the early 19th century , war was brewing between Napoleon I and the Russian Tsar Alexander I , and Napoleon saw the shared interests of Britain and Russia in defeating him as a threat . Napoleon ' s advisor , the Duke of Cadore , recommended that the ports of Europe be closed to the British , stating that " Once in Cadiz , Sire , you will be in a position either to break or strengthen the bonds with Russia " . Soult and his French army invaded Portugal in 1809 , but were beaten by Wellesley at Oporto on May 12 . The British and Spanish armies advanced into mainland Spain , however a lack of faith in the Spanish army forced Arthur Wellesley to retreat back into Portugal after Spanish defeats in the Battle of Ocana and Battle of Alba de Tormes . By 1810 , the war had reached a stalemate . Portuguese and Spanish positions were strengthened by Wellesley with the construction of the Lines of Torres Vedras , and the remainder of the Spanish forces was forced back to defend the Spanish government at Cádiz against Soult ' s Army of Andalusia . The port of Cádiz was surrounded on land by the armies of Soult and Victor , in three entrenched positions at Chiclana , Puerto Real and Santa Maria , positioned in a semicircle around the city . In the case of the former position , only an area of marshland separated the forces . The French initially sent an envoy with a demand for surrender , however this was refused . The resulting bombardment of the Spanish coastal city involved some of the largest artillery pieces in existence at the time , including " Grand Mortars " , which were so large they had to be abandoned when the French eventually retreated , and fired projectiles to distances previously thought impossible , some up to 3 miles in range . ( The " Grand Mortar " was placed in St . James ' s Park in London as a gift to the British in honour of the Duke of Wellington . ) The French continued to bombard Cadiz through to the end of 1810 , however the extreme distance lessened their effect . The terrain surrounding the strong fortifications of Cádiz proved difficult for the French to attack , and the French also suffered from a lack of supplies , particularly ammunition , and from continuous guerrilla raiding parties attacking the rear of their siege lines and their internal communications with Andalusia . On many occasions , the French were forced to send escorts of 150 – 200 men to guard couriers and supply convoys in the hinterland . So great were the difficulties that one historian judges that ; French reinforcements continued to arrive through to April 20 , and the capture of an outer Spanish fort guarding the road through to the Puerto Real helped to facilitate the arrival of these forces . This captured fort also provided the French which a vantage point to shell ships coming in and out of the besieged Spanish port . During 1811 , Victor ' s force was continually diminished because of requests for reinforcement from Soult to aid his siege of Badajoz . This reduction in men , which brought the French numbers down to between 20 , 000 – 15 , 000 , encouraged the defenders of Cádiz to attempt a breakout . A sortie of 4 , 000 Spanish troops , under the command of General José de Zayas , was arranged in conjunction with the arrival of an Anglo - Spanish relief army of around 16 , 000 troops that landed 50 miles to the south in Tarifa . This Anglo - Spanish force was under the overall command of Spanish General Manuel La Peña , with the British contingent being led by Lieutenant - General Sir Thomas Graham . On February 21 , 1811 the force set sail for Tarifa , and eventually landed at Algeciras on February 23 . Eventually marching towards Cádiz on February 28 , the force met a French detachment of two French divisions under Victor at Barrosa . While the battle was a tactical victory for the Allied force , with a French regimental eagle captured , it was strategically indecisive . Smaller sorties of 2 , 000 – 3 , 000 men continued to operate out of Cadiz from April to August 1811 . On October 26 , British naval gunboats from Gibraltar also destroyed French positions at St . Mary ' s killing French artillery commander Alexandre - Antoine Hureau de Sénarmont . An attempt by Victor to crush the small Anglo - Spanish garrison at Tarifa over the winter of 1811 – 1812 was frustrated by torrential rains and an obstinate defence , marking an end to French operations against the city ' s outer works . On July 22 , 1812 , Wellesley won a tactical victory over Auguste Marmont at Salamanca . The Spanish , British and Portuguese then entered Madrid on August 6 and advanced towards Burgos . Realising that his army was in danger of being cut off , Soult ordered a retreat from Cádiz set for August 24 . After a long artillery barrage , the French placed together the muzzles of over 600 cannons , to destroy them . While these guns were rendered unusable to the Spanish and British , the Allied forces did capture 30 gunboat s and a large quantity of stores . References . Printed Sources : Websites :