The British invasions of the Río de la Plata (Invasiones Inglesas del 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 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 were 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 occupied Montevideo, following the Battle of Montevideo (1807), 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 in Buenos Aires were killed or wounded, the British were forced to withdraw.
The resistance of the local people and their active participation in the defence, with no direct support from the Spanish Kingdom, were important steps toward the May Revolution in 1810, and the Argentine Declaration of Independence in 1816.
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. Since the beginning of the Conquest of Americas, England had been interested in the riches of the region. The Peace of Basel in 1795, ended the war between Spain and the French Revolution. In 1796, by the Second Treaty of San Ildefonso, Spain teamed up with France, which was at war with England, thus opening the gap that would justify military action from Britain, who judged was the right moment after the defeat of the Franco-Spanish Armada in Battle of Trafalgar which saw the end of the Spanish naval supremacy.
The Spanish Viceroy, Marquis Rafael de Sobremonte, had asked the Spanish Crown for reinforcements many times, but no new men arrived. It was suggested that he should arm the city residents of Buenos Aires, then a large settlement housing approximately 45,000, to form a militia, but he was reluctant to give weapons to the Creole population.
The British took Quilmes, near Buenos Aires, on 25 June 1806, and reached and occupied Buenos Aires on the 27 June. The Viceroy fled to Córdoba Province with the city's treasury, but lost it to British forces during his escape. His mismanagement of the situation alienated him with the population of Buenos Aires; they later opposed, and prevented, his reinstatement as a Viceroy after the end of the war.
The residents of the city were pleased to see the British arrive at first, although some feared becoming a British colony and favoured independence. However, one of the first measures of Beresford was to decree free commerce and reduction of port taxes. These measures displeased the merchants, who benefited from the Spanish monopoly, and so they gave their support to the resistance.
French marine officer Santiago de Liniers y Bremond, at the time an acting officer of the Spanish navy, organised the re-conquest of Buenos Aires from Montevideo, with help of the city governor, Ruiz Huidobro. Also of importance was the participation of Juan Martín de Pueyrredón, chief of the creole urban militias.
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. After two days of fighting, Beresford surrendered on 12 August. Two days later, the government at the Buenos Aires Cabildo named Liniers military and political chief of the city.
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 3 February 1807, Montevideo was captured in a joint military and naval operation using British reinforcements of 8,000 men under General Sir Samuel Auchmuty and a naval squadron under Admiral Sir Charles Stirling.
On 1 July, Liniers was defeated in the environs of the city. 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. Finally, 3 days after defeating Liniers, 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 determined militia, 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 of the city overwhelmed the British troops.
By the end of 5 July, the British controlled Retiro but the city's centre was still in the hands of the defenders, and the invaders were demoralized. At this point, a counter-attack by the Buenos Aires militia 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 having more than half his forces killed and captured, Whitelocke signed a ceasefire with Liniers on 12 August. He 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-martialled and cashiered, mainly for surrendering Montevideo. Liniers was later named Viceroy of the Río de la Plata by the Spanish Crown.