When Napoleon Bonaparte seized power of France, crowning himself as "Emperor of the French", Europe saw itself in a major war. Napoleon made the nation of France into a military dictatorship and began his conquest of taking over Europe. He made alliances with many other European nations one of which was none other than the Kingdom of Spain, due to the fact both the French and the Spanish both had a grudge against the British Empire.
This of course led to many colonists and settlers throughout Spanish Latin America to rebel, due to the fact people did not wish to have to pay higher taxes on goods due to Spain being at war, fearing British invasions of the Spanish colonies, and the feeling that Spain had abandoned them in the New World. At first plenty of rebellions were crushed throughout Latin America and rebel armies were simply small in numbers ranging from thousand to six thousand.
In 1806, sensing that the Spanish colonies in South America would be freed from Spanish rule and that there were riches waiting, British soldiers under the initiative of Home Riggs Popham and the command of William Carr Beresford invaded the colonial city of Buenos Aires. At first, they beat the
Criollos there, with the viceroy of Rio de la Plata, the Marquis of Sobremonte, having fled; but after 2-3 months, the criollos got a new leader, Santiago de Liniers, to fight back against the British. Eventually the British became aware of this and sent an expeditionary force under the command of first Samuel Auchmuty and then John Whitelocke to reinforce the British soldiers already there.
First, they captured the Spanish colonial city of Montevideo in the month of February 1807, under Auchmuty’s command. Then on July 2nd and 3rd that year, with Whitelocke having taken command some months earlier, Buenos Aires was captured from the criollos after a very fierce fight at the Corral de Miserere and then in the city center. The victory was made possible because unlike in our world, Genera; Whitelocke garrisoned the 36th and 88th regiments of the British Army, which had been cooped up in ships for 9 or more months, and the 6th Dragoon Guards, with their awkward cavalry boots, in Montevideo. Instead, the 47th regiment, part of the 36th, and some of the 20th and 21st Light Dragoons, which were all more experienced, fought in Buenos Aires alongside all the other British soldiers who were present in Buenos Aires. That arrangement enabled the British forces in Buenos Aires to remain more united and for the generals to communicate more easily, translating into more success on the field.
Meanwhile, other cities along the Rio de la Plata basin, such as Rosario and Santa Fe, capitulated to the British after little to no fighting, and Whitelocke’s soldiers, especially in Robert Craufurd’s brigade, were about to cross the Andes or sail around the Strait of Magellan to capture Chile. However, they encountered heavy Spanish resistance in some parts of the northeast and in Mendoza and other cities in the Tucuman region. They met even greater resistance in Cordoba and in cities in the north, like Salta, Tucuman, and various cities in Upper Peru (now Bolivia), plus those in and around present-day Paraguay. Therefore, the soldiers abandoned their plans to invade Chile, and instead concentrated on those cities instead. These battles were led by the likes of Auchmuty and Craufurd, with Beresford, Pack, Mahon, and Lumley playing important roles too, even as Whitelocke was made as Rio de la Plata’s governor, which the Spanish colonials and natives did not like. As a matter of fact, Auchmuty rose to be second-in-command to Whitelocke after the previous one, Leveson-Gower, was found to be incompetent in the 1807 invasion of Buenos Aires and was subsequently switched to leading the British garrison in Buenos Aires.
Battles raged on between the British soldiers on the one hand and the locals plus the Spaniards on the other hand between 1807 and 1812. This struggle was known as the
Anglo-Plata War. From 1807 to 1809, it mostly took place in the Pampas/Uruguay and in the Cordoba region; from 1809 to the end, the theater of the war shifted to Upper Peru/Jujuy/Tucuman and Paraguay. In all these places, battles took place against rural
caudillos, or warlords, as well as in the cities especially in cities like Santa Fe and Cordoba.
From 1806 onwards they were part of the Anglo-Spanish Wars, which were fought around the world, in the context of the Napoleonic Wars of the early 1800's. Just like in the Peninsular War in Spain and Portugal, so outside the Viceroy of Rio de la Plata, most of the Spanish-speaking commoners supported the British and the deposed the king of Spain (Ferdinand VII) due to the fact he was careless ruler and was allied with Joseph Bonaparte (Napoleon’s brother), who invaded Portugal in 1808 and thereby weakened Spain’s ties to the Americas even more. In Rio de la Plata, many of the criollos still supported Spain until around 1815, because they didn't like British rule. In fact, a number of criollos in British occupied Rio de la Plata fled in big numbers to Chile, where they were known as
Rioplatenses; they joined the Spanish-American wars of independence. Many other criollos that decided to stay in Plata though, came to accept British rule relatively quickly, and those who did accepted British authority quickly were mostly the youth.
The British forces won within most of Rio de la Plata, but in Upper Peru and Paraguay, the Spanish forces gained victory. That cleared the way for the Congress of Vienna in 1814-15 to give Upper Peru and Paraguay back to Spain, but for the British to keep the rest of occupied Rio de la Plata. Once that was completed, there were lingering skirmishes from the Anglo-Plata War in Paraguay over access via the Parana River, and Paraguay became a short-lived British protectorate in 1818, only for it gain independence in 1824.
But as a result Spain lost one of it's important colonies in the New World to the British. And with the loss of the Viceroy of Rio de la Plata, the nation of Spain suffered greater debt than it had ever seen before. Being defeated in the Napoleonic Wars, led to the economy suffering massive debt and it knew that the colonies it still barely controlled in the New World would end up becoming independent entities of their own, and Spain could do so little about it.
Glossary
Anglo-Plata War - (noun) the struggle in which the British had to fight against rebels and resistance across occupied Rio de la Plata lasting from the year 1807-1809.
caudillo(s) - (noun) (in Spanish-speaking regions) a military or a political leader.
criollo(s) - (noun) in modern times it has plenty of meanings, but originally it was the term used for people across Latin America would had full or near-full Spanish descent which separated them from Latin Americans with multi-racial origins and Latin Americans with non-Spanish origins from Europe.
Rioplatense -
(noun) the original Spanish speaking inhabitants of Plata, they were the first Europeans to arrive and colonize Rio de la Plata long before the British came and took over it during the Napoleonic Wars. Some did flee to other parts of Spanish Latin America like mentioned in the article above, but a majority decided to stay in British owned Rio de la Plata and eventually came to accept British rule.