River Plate

OTL; 1808; Sir Arthur Wellesley, who latter history would remember as Duke of Wellington, gathered a fleet an 10.000 men in Cork, Ireland, ready to attack for a third time the city of Buenos Aires, two times failed to be captured permanently. This time, Wellington was planning to ally with the creoles against the spaniards, so he would arrive Rio de la Plata not as an invader, but a liberator. His further plan was to help Francisco de Miranda in making his dream true: liberating the spanish America and create an empire.

Suddenly, the whole set of alliances changed: Napoleon invaded Spain, starting the Peninsular War, so the british became allies of Spain, and their obligation as such was to stop any attack on their colonies and help them throwing the invader out of their homeland.

This is the history of what would had happened if the british decided it was too late to change allies or, no matter the alliances, the spanish colonies ahd to be invaded in order to secure such a potential region of commercial influence, and proceed with the Third Invasion to Rio de la Plata.

Tercera Invasión Inglesa: La Conquista (Third English Invasion: The Conquest)
It was 7th July 1808 when Wellesley's fleet arrived the port of Quilmes, where both artillery and cavalry could disembark safely. Viceroy Santiago de Liniers was already prepared to reject this invasion, as he did with the last one, the past year.

However, he was not prepared to see commander Manuel Belgrano, Secretary of the Consulate, occupying the cabildo by force and taking him prisioner. An internal struggle began, when the Chief of the Regiment of Patricians, Cornelio Saavedra, main supporter of Liniers, tried to capture the cabildo. But his effort prooved useless when he found himself out surrounded by rebel creole troops commanded by Belgrano and his cousin Juan José Castelli, and the british forces of Sir Arthur Wellesley.

By the next day, the city was completely taken by the british. Some spaniards achieved to flee the city prior to the arrival of Wellesley. The most noticed, Martín de Álzaga, wrote a letter to his friend Francisco Javier de Elío, leader of the junta of Montevideo, who didn't recognise Liniers' government on Buenos Aires. Some days after, the Rio de la Plata was a battlefield, disputed between the british/creoles from Buenos Aires and the spaniards/loyalists from Montevideo.

The creole generals Juan Martín de Pueyrredón and José Rondeau led the warring efforts of Buenos Aires in the Eastern Bank (Banda Oriental, OTL Uruguay), while Wellesley and the patriots met at Buenos Aires to find a way to invade the Bank and secure the Rio de la Plata under british-patriot joint control.