British invasions of the Río de la Plata The British invasions of the Río de la Plata were a series of unsuccessful British attempts to seize control of the Spanish colonies located around the La Plata Basin in South America ( today part of Argentina and Uruguay ) . The invasions took place between 1806 and 1807 , as part of the Napoleonic Wars , when Spain was an ally of France . The invasions occurred in two phases . A detachment from the British army occupied Buenos Aires for 46 days in 1806 before being expelled . In 1807 , a second force stormed and occupied Montevideo , remaining for several months , and a third force made a second attempt to take Buenos Aires . After several days of street - fighting against the local militia and Spanish colonial army , in which half of the British forces were killed or wounded , the British were forced to withdraw . The social effects of the invasions are among the causes of the May Revolution . The criollos , who had so far been denied important positions , could get political strength in military roles . The successful resistance with little help from the peninsula fostered the desire of self - determination . An open cabildo and the Royal Audience of Buenos Aires deposed the viceroy Rafael de Sobremonte and designated instead the popular hero Santiago de Liniers , which was a complete unprecedented action : before that , the viceroy was only subject of the King of Spain himself , and no Spanish American had authority over him . Background . Pedro de Mendoza founded the " Ciudad de Nuestra Señora del Buen Ayre " ( " Our Lady of the Fair Winds " ) on 2 February 1536 as a Spanish settlement . The site was abandoned in 1541 , but re - established in 1580 by Juan de Garay with the name " Ciudad de la Santísima Trinidad y Puerto de Santa María del Buen Ayre " , and the city became one of the largest in the Americas . A Portuguese colony was founded nearby at Colonia del Sacramento in 1680 . To deter Portuguese expansion , the Spanish founded Montevideo in 1726 , and Colonia was finally ceded to Spain under the Treaty of San Ildefonso in 1777 , one year after the creation of the Spanish Viceroyalty of the Río de la Plata , the forerunner of modern Argentina . The South Sea Company was granted trading concessions in South America in the time of Queen Anne , under the Treaty of Utrecht . The British had long harboured ambitions in South America , considering the estuary of the Río de la Plata as the most favourable location for a British colony . The Napoleonic Wars played a key role in the Rio de la Plata conflict and since the beginning of the conquest of the Americas , England had been interested in the riches of the region . The Peace of Basel in 1795 ended the war between Spain and France . In 1796 , by the Second Treaty of San Ildefonso , Spain joined France in its war with Britain , thus giving Britain cause for military action against Spanish colonies . Britain judged it the right moment after the defeat of the Franco - Spanish fleet at the Battle of Trafalgar . This battle forced Spain to reduce to a minimum its naval communications with its American colonies . Historically , Buenos Aires had been relatively neglected by Spain , which sent most of its ships to the more economically important city of Lima . The last time when a significant Spanish military force had arrived in Buenos Aires was in 1784 . British interest in the region . There were six Anglo - Spanish War s from 1702 to 1783 , most of which lasted for several years and Britain had long harboured interests in taking control of the region from the Spanish before the invasions . Back in 1711 , John Pullen stated that the Río de la Plata was the best place in the world for making a British colony . His proposal included Santa Fe and Asunción , and would have generated an agricultural area with Buenos Aires as the main port . Admiral Vernon also declared the benefit of opening markets in those areas in 1741 . By 1780 the British government approved a project of colonel William Fullarton to take the Americas with attacks from both the Atlantic ( from Europe ) and the Pacific ( from India ) . This project was cancelled . Nicholas Vansittart made a new proposal in 1796 : the plan was to take Buenos Aires , then move to Chile and attack from there the Spanish stronghold of El Callao in Peru . This proposal was canceled the following year , but was improved by Thomas Maitland in 1800 as the Maitland Plan . The new plan was to seize control of Buenos Aires with 4 , 000 soldiers and 1 , 500 cavalry , move to Mendoza , and prepare a military expedition to cross the Andes and conquer Chile . From there , the British would move from sea to seize Perú and then Quito . All these proposals were discussed in 1804 by William Pitt , Lord Henry Melville and Sir Home Riggs Popham . Popham did not believe a complete military occupation of South America was practical but argued for taking control of key locations to allow the main objective , to open new markets for the British economy . Although there was consensus for weakening Spanish control over its South American colonies , there was no agreement as to the system and the moment to take such action . For instance , it was not even agreed whether the cities be turned into British colonies after their capture or just be made into British proctectorates . First invasion . In 1805 Popham received orders to escort the David Baird - led expedition against the Dutch colony of the Cape of Good Hope , which was allied with Napoleon . With nearly 6 , 300 men they took it in January 1806 . Popham received new orders from the admiralty to patrol the east coast of South America , from Rio de Janeiro to the Río de la Plata , in order to detect any attempt to counterattack the Cape . However , Popham had the idea of taking the Río de la Plata with a military action similar to the one made at the Cape . His agent William White had him informed about the local politics of the city , such as the discontent among some groups about the restrictive regulations enforced by Spain about international commerce . Popham manifested Baird his will to take the zone , with or without his help . Baird gave him the 71st Regiment of Infantry , artillery and 1 , 000 men to attempt the invasion . Baird promoted William Carr Beresford to general and designated him vicegobernor of the zone if it was taken . The expedition got reinforcements of 1 , 500 men and 36 officials at Saint Helena . The Spanish Viceroy , Marquis Rafael de Sobremonte , had asked the Spanish Crown for reinforcements many times , but only received a shipment of several thousand muskets and instructions to form a militia . Buenos Aires was then a large settlement housing approximately 45 , 000 , but the Viceroy was reluctant to give weapons to the Creole population . The best troops had been dispatched to the Upper Peru currently Bolivia to guard the frontiers from Túpac Amaru II ' s revolt , and when Sobremonte learned of the British presence in the area he dispatched the remaining troops to Montevideo , considering that the attack would be in that city . Thus , the British found Buenos Aires almost defenseless . The British took Quilmes , near Buenos Aires , on 25 June 1806 , and reached and occupied Buenos Aires on 27 June . The Viceroy fled to Córdoba with the city ' s treasury , but lost it to British forces during his escape . Although his action was in line with a law enacted by former Viceroy Pedro de Cevallos , which required the treasury to be kept safe in case of a foreign attack , he was seen as a coward by the population because of it . The wealthy members of society were not pleased with the British arrival . nevertheless the politicians swore loyalty to them , such as the members of the Cabildo or the Consulates , with the exception of Manuel Belgrano who said " Queremos al antiguo amo o a ninguno " ( we want the same Master or none at all ) , leaving to the Banda Oriental , now Uruguay . Religious leaders swore loyalty as well , after securing the promise that the catholic religion would be respected . The Real Audience ended its activities . The rich people included the British among their celebrations , and those promised that their slaves wouldn ' t be emancipated . However , the bulk of the population did not like the new situation and rejected the British . Merchants were also displeased by the repeal of the Spanish monopoly of commerce and the opening to free trade , as it harmed their interests ; one of their leaders was Martín de Álzaga . De Álzaga organized the digging of a secret tunnel to the fort , where the British were located , with the purpose of filling it with explosives and attacking the invaders by surprise . Juan Martín de Pueyrredón organized a militia near the city , but was discovered before being ready , and his troops were defeated . Santiago de Liniers , who was assigned to guard a nearby coast defense , got into the city and weighted the situation . He convinced Álzaga to hold on his plan , and moved to Montevideo . The governor Ruiz Huidobro gave him command of 550 veterans and 400 soldiers to return to Buenos Aires and attempt the re - conquest . Sobremonte was doing the same in Córdoba , but Liniers got to Buenos Aires first . On 4 August 1806 , Liniers landed at Las Conchas , north of Buenos Aires , and advanced with a mixed force of Buenos Aires line troops and Montevideo Militia toward the city . On 10 August he took control of the strategic points of Miserere and El Retiro , holding the north and west entries to the city . Beresford finally surrendered on 14 August . An open cabildo decided afterwards to depose Sobremonte from having military authority , and giving instead such authority to the victorious Liniers . As pointed , Sobremonte ' s departure at the beginning of the war made him highly unpopular among the peoples of Buenos Aires . Sobremonte would not return to Buenos Aires , and move to Montevideo instead . The open cabildo decided as well to prepare the city against the possibility of a British counter - attack . Foreseeing the possibility of a second invasion , militias were formed by the Spanish and criollos , such as the Patricios , Arribeños , Húsares ( of Pueyrredón ) , Pardos and Morenos . The creation of such local forces created concern within the Spanish elite , fearful of an attempt of secession from the Spanish Crown . On this first invasion , the 71st Regiment of Foot lost both of its Regimental Colour s during the combat , which are currently held in Argentina . On the second invasion , there was a frustrated attempt to recover both flags . They were retaken by the Buenos Aires militia and returned to the Santo Domingo convent . Another two banners from the British Royal Navy are also held in the convent . Second invasion . Battle of Montevideo . On 3 February 1807 Montevideo , defended by approximately 5 , 000 men , was besieged at 2 : 00am by a 6 , 000 strong British force in a joint military and naval operation under General Sir Samuel Auchmuty and a naval squadron under Admiral Sir Charles Stirling . Reinforcements for the defenders came en route from Buenos Aires , so that the rapid success of the operation was essential . Swiftly breached , the city was then assaulted by the 40th regiment and the elite 95th ( Rifle ) regiment . Once inside the walls , the British met heavy resistance as the Spanish fought to halt their advance , but they gradually spread out and forced back the defenders . On the other side of the city a second assault was launched , spearheaded by the 87th Regiment of Foot taking the Spanish defenders in the rear . The Spanish Governor Ruiz Huidobro accepted Auchmuty ' s demand of unconditional surrender around 5 : 00 A . M . The Spanish took 1 , 500 casualties and a further 2 , 000 were taken prisoner while the British had taken 600 casualties . On 10 May , Lieutenant - General John Whitelocke arrived in Montevideo to take overall command of the British forces on the Río de la Plata , landing on 27 June . 2nd Battle of Buenos Aires . On the 1 July , the force led by Liniers fought bravely but was overwhelmed by superior numbers in the city environs . At this crucial moment , Whitelocke did not attempt to enter the city , but twice demanded the city ' s surrender . Meanwhile , Buenos Aires ' mayor Martín de Álzaga organised the defence of the city by digging trenches , fortifying buildings and erecting fences with great popular support for the Creoles hungered for independence . Finally , 3 days after forcing the troops under Liniers to retreat , Whitelocke resolved to attack Buenos Aires . Trusting in the superiority of his soldiers , he divided his army into 12 columns and advanced without the protection of the artillery . His army was met on the streets by a mixed race militia , including 686 African slaves , stiffened by the local 1st Naval Infantry Battalion and 1st ' Los Patricios ' Infantry Regiment , and fighting continued on the streets of Buenos Aires on 4 July and 5 July . Whitelocke underestimated the importance of urban combat , in which the inhabitants employed cooking pots filled with burning oil from rooftops , injuring several redcoats of the 88th Regiment . The locals eventually overwhelmed the British troops . By the end of 5 July , the British controlled Retiro and Residencia at the cost of about 70 officers and 1 , 000 other ranks killed or wounded , but the city ' s centre was still in the hands of the defenders , and the invaders were now demoralized . At this point , a counter - attack by the militias and colonial troops present , defeated many important British commanders , including Robert Crauford and Dennis Pack . Then Whitelocke proposed a 24 - hour truce , which was rejected by Liniers , who ordered an artillery attack . After suffering 311 killed , 679 wounded and 1 , 808 captured or missing , Whitelocke signed an armistice with Liniers on 12 August ; the local marines playing an important part in defeating Brigadier - General Robert Crauford and his two thousand redcoats at the Battle of Plaza del Mercado which is now recalled by the people of Buenos Aires as ' The Defence ' . Whitelocke left the Río de la Plata basin taking with him the British forces in Buenos Aires , Montevideo , and Colonia . On his return to Great Britain , he was court - martial led and cashiered , mainly for surrendering Montevideo . Liniers was later named Viceroy of the Río de la Plata by the Spanish Crown . Towards independence . Having to fight the British invasions by themselves , with little direct help from the Spanish Crown , and given that the Spanish King was captured by Napoleon , the idea of independence from Spain grew stronger . Less than three years after the second invasion , the May Revolution took place in 1810 , as a prelude to the Declaration of Independence of Argentina of 1816 .