Chapter 10 - The Invasion of Perú
José de San Martin, Brigadier General of the United Provinces, Commander of the Army of the North, and Liberator of Perú
When San Martin had arrived in Buenos Aires in 1812, he joined the ongoing revolution with a single goal in mind: the total liberation of Latin America from Spanish colonial rule. Exposed to both fighting of a standard unlike anything the Americas had seen since the American Revolutionary War and to liberal ideas unlike anything the Spanish colonies had experienced, he represented in some ways the typical contradictions of his generations. Initially a reluctant supporter of independence as an inevitable response to the Spanish promise to reimpose the traditional colonial order on the colonies, he departed for Alto Perú in 1814 committed to the aims of its most radical proponents, and began meticulously planning for the invasion of Perú, last and greatest bastion of Spanish power in the southern cone.
Finding the Army of the North in perilously bad shape after years of non-stop skirmishing with small detachments up and down the front, he settled in for what he envisioned would be the long process of turning a hastily-gathered rabble meant to prevent the north from falling to the royalists into a real army capable of taking the offensive against Lima. His first steps involved reorganizing the defenses of the region, recognizing Castelli’s cavalry commander Juan Martin de Güemes’ talents immediately upon his arrival[1] and putting the gaucho leader in charge of the guerrilla forces meant to deter further royalist incursions past Lake Titicaca.
Now more or less secure in his defensive positions, he began the arduous task of professionalizing his infantry, which - like most of the infantry in the revolutionary armies - consisted primarily of emancipated slaves, criollo militias and native detachments which, though numerous, tended to lack modern equipment and training. The first fruits of these efforts were the country’s first professional sapper corps, which would serve with distinction in the final phase of the Chilean independence war alongside Las Heras’ expedition.
When the war with Brazil was starting in 1816, his efforts were almost complete, but he would be disappointed by both the government in La Plata and Santiago: nearly half his cavalry was redeployed to Uruguay, alongside the recently returned sappers, and his Chilean counterparts likewise redirected efforts to the south in response. But he would not sit idly while the fighting raged in the Littoral provinces: Las Heras’ expeditionary force, 1,200 strong and with 3 years of experience at that point, was folded into the Army of the North, which now had a strength of nearly 10,000 men on paper (although only 6,000 of those were properly enlisted or on the government’s payroll), and continued organizing his army along European lines.
When the order to invade finally arrives in mid-1819, the army he leads is truly formidable: it has been thinned down to its professional core, with many of the criollo and native militiamen either being resettled elsewhere or formally enlisted, but still numbered nearly 8,000: all told, he had molded his infantry into a powerful contingent 6,000 strong running the gamut from grenadiers to military engineers and rifle-armed
chausseurs. The remaining 2,000 soldiers officially under his command included both the European style
cuirassiers and mounted grenadiers he’d helped train and the mobile and relentless gauchos under Güemes and Manuel Artigas who’d spent the last 6 years in almost constant combat. His army was also supplemented by a Chilean expeditionary force, totaling another 4,000 men under the command of Bernardo O’Higgins and fresh off their conquest of the last royalist stronghold to Chile’s south.
But for all the combined might of the Platine and Chilean armies, which would be reinforced by the militias of the still-extant revolution in Cuzco, their success depended more on the combined fleets of the Chile and the United Provinces, which were placed under the command of the Scottish commander Thomas Cochrane. Fresh off its baptism of fire in the conquest of Chiloe, the Chilean navy was instrumental in San Martin’s invasion plan, finally giving the revolutionaries a naval contingent capable of more than just raiding the coast or preying on royalist shipping.
Just as San Martin had dedicated the time since the liberation of Chile to training his army, so too had the government in Chile embarked on an ambitious naval armament plan which forced the remnants of the Spanish navy in Peru to hide in its ports and allowed it to subdue the heavily fortified islands south of Valdivia. It would also mark the beginning of the invasion of Perú with a bold attack right at the heart of the viceroyalty, placing the port of Callao under blockade in the early weeks of 1820 and capturing the royalist flagship - the frigate Esmeralda - in a daring assault that neutralized the last major naval threat against the invasion.
The capture of the royalist flagship Esmeralda by Chilean sailors in a daring attack
With the port under siege and the Spanish fleet trapped by Cochrane, the combined Platine, Chilean and Cuzcan attacked the viceroyalty from both land and sea; landing at the head of a Platine-Chilean invasion at the Bay of Pisco, San Martin would take personal command of the invasion and would march towards Lima - whose port remained under blockade - in February of 1820, forcing the royalists to confront him or risk getting trapped in the capital with a quarter of the Royal Army of Peru and the viceroy.
Sallying under the command of Brigadier Osorio, they moved to intercept San Martin before he could cut off Lima from the rest of the interior; despite a heavy numerical advantage, the united revolutionary armies were unwieldy and of varying quality, while Osorio commanded over 5,000 veterans. The invading army made slow progress on the march, and were caught early in the morning by Osorio’s attack, spreading panic through the revolutionary ranks and neutering their superiority in numbers - nearly 2,000 militiamen would simply desert the field when attacked that morning - before San Martin and his subordinates were able to restore order in their ranks.
It was a shocking start to the campaign: although his casualties were relatively light and he was able to withdraw from the field of battle with most of his professional formations mostly intact, the 2,000 deserters wouldn’t rejoin the army before it faced Osorio’s detachment again, and most damaging to his campaign, the surprise attack robbed him of a third of his artillery[2]. But it was simply not enough: rallying over 8,000 troops, he took the offensive against Osorio this time, and forced the Spanish to take up desperate defensive positions as he used his advantage in numbers to try and outflank the royalists.
After long, grueling fighting, which cost the revolutionary army 800 dead and nearly twice as many wounded, the Spanish were beaten and what remained of Osorio’s army limped back to Lima. San Martin’s army had not only made good the loss of his artillery by capturing over a dozen of the Spanish pieces, it had also decimated Osorio’s forces: of the 5,000 soldiers the royalists arrayed for battle in the second battle of Pisco, 1,000 laid dead on the field, another thousand wounded, and 2,000 in total surrendered to the revolutionaries along with what remained of their ammunition and supplies[3].
The Viceroy in Lima, Joaquín de Pezuela, attempted to negotiate, and while San Martin agreed to parley, talks broke down almost immediately: Pezuela’s offer to “restore” the Cadiz Constitution of 1812 seemed of little of value to the revolutionaries, who’d held large swathes of southern Peru for longer than the constitution was in force, and it proved to be the last straw for the leaders of the royalist army in Perú, which would mutiny at the news of talks with the revolutionaries and force Pezuela to resign in April.
As San Martin made his final approach to the city, he was shocked to discover the drastic steps the mutineers had taken: abandoning Lima with the majority of the garrison, its food stores, its supplies, and most importantly, its treasury, the revolutionaries arrived to find a city wracked by fear and convulsing from brutal fratricidal fighting that would leave the majority of its Spanish population dead or exiled. But the fear gave way to exuberant celebrations as San Martin made his terms to the city public: his offer to recognize the rank and seniority of the remaining garrison prompted them to surrender immediately, and the city’s leaders acquiesced without hesitation to his condition that they convene a Cabildo Abierto of their own.
San Martin entered the city on the 25th of May[4] accompanied by leaders from Cuzco and settled in to garrison the city as its Cabildo gathered. Emulating the May Revolution of Buenos Aires, the Cabildo of Lima proclaimed a governing Junta presided over by the Peruvian general José de la Mar and sent out summons for a constitutional assembly, but they would take a further step that their Platine counterparts presided by Saavedra had failed to do ten years prior: on June 1st, 1820, the assembled delegates proclaimed Perú’s independence from Spain.
Although some fighting would continue, royalist power in South America had been smashed to pieces: the remnants of the viceroyalty’s army were dispersed throughout the countryside, trekking north as quickly as they could to the last redoubt of royal authority left, Quito. The Royal Army of Perú had numbered as many as 20,000 when the revolution had begun, but after a decade of heavy fighting and bloodletting across the Alto region, only half that many would manage to gather, exhausted and demoralized, in Quito. Formidable as the remaining royalist army was, it was soon trapped in Quito, as the rapid collapse of the Viceroyalty had only hastened an uprising that had been brewing in Guayaquil for years, culminating in the creation of the Free State of Guayaquil on October 9, 1820. The mighty Spanish Empire, which had controlled South America from the Darien Gap in Panama to the Strait of Magellan in Patagonia and the continent on two oceans and the Caribbean, was reduced to the outskirts of Quito by the end of the year as Gran Colombia consolidated its independence from Madrid the year before.
The Second Battle of Pisco definitively broke the back of Spanish power in South America
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[1] San Martin was only very briefly commander of the Army of the North IOTL, being replaced more or less immediately by Belgrano due to his own health problems, but despite that brief stint in command, he immediately recognized Güemes talents and the effectiveness of his tactics to defend against invasion. It was in the context of defending Salta and Jujuy IOTL, but it would be just as true in the Upper Perú.
[2] Instead of going to Chile ITTL, Osorio was forced to stay behind and fight the longer-lasting Cuzco rebellion, which has survived primarily because the UP treats it as if it were its front line of defense. The battle I’m describing is based on OTL’s Battle (or Disaster) of Cancha Rayada.
[3] Like First Pisco is based on Cancha Rayada, Second Pisco is based on the Battle of Maipú
[4] Ok, I admit this one is the biggest stretch, since it has involved the biggest alteration from OTL: the army arrived on July 9 IOTL. But I couldn’t resist the temptation of having Lima call for a Cabildo Abierto on the 10th anniversary of Buenos Aires’.