Shortly after independence, Peru and Bolivia were unified into a Confederation. That in itself was a strange outcome.
Bolivia had been freed by Simon Bolivar's second campaign. My recollection is that after the Gran Colombia thing, the Bolivian's called Bolivar down to help them out, and he actually came. They were so greatful they named the country after him.
Peru in contrast was the most conservative of the Spanish colonies and actually fought to remain with Spain for a while.
Anyway, somehow, Bolivia and Peru got stapled on up together. The resulting conglomerate scared the piss out of Chile and Argentina, who fought simultaneous separate campaigns called 'The War of the Confederation', until the Confederation just said 'fuck it' and everyone took their toys and went home.
I'm just going on memory here, so I'm happy enough to be contradicted if anyone wants to throw in something more accurate and nuanced.
Not a contradiction, only an elaboration. Peru and Bolivia had until 1776, when the Province of Charcas was transferred to the new Viceroyalty of La Plata, been united politically. Cultural and economic links transcended the separation and have remained, debatably, existent until the present day. The beginning of this “union” is lost in the darkness of American prehistory, but we can find safe footing to argue for it from at least the XVth century on.
When it came to the wars of Liberation, in 1810,
before the proclamations of uti possidetis were adopted by the American republics, the royal armies from Peru had reconquered the territory of Charcas from La Plata, and re-annexed it to Peru. After the Spaniards had been vanquished everywhere else, the Viceroy and the remaining troops still ruled the highlands of southern Peru and Bolivia, maintaining the unified political control of the area.
Now, after the final extinction of Spanish power with the death of the last Viceroy Pedro Antonio Olañeta following the battle of Tumusla on April 1st 1825, all of Peru (OTL Peru and Bolivia) had been liberated. In July of that same year an Assembly of representatives of all the provinces of “Upper Peru” (Bolivia) met in Chuquisaca, in order discuss their “independence.”
Here’s where things get iffy. The assembly was originally called by Antonio Jose de Sucre, one of Bolivar’s most trusted lieutenants, in February, before the Spaniards were defeated. Yet it met anyway, and in Chuquisaca, which was a pauper town, not an urban center like La Paz or Cochabamba. Furthermore, out of the 48 delegates, 30 were “landowners” of the surrounding regions. The issues discussed were: complete independence, to
remain with Peru, or reunion with La Plata. Only the outnumbered delegates from La Paz voted against independence. Also, no sooner had the decision been made that the Presidency was offered to Bolivar, who in turn gave it to Sucre, who had conveniently remained in Chuquisaca, after just a few months.
Opposing all of these developments were men like Agustin Gamarra in Peru, and Andres de Santa Cruz in Bolivia, who sought to reunite the two states. Ultimately Santa Cruz would succeed, and defeat the Argentinians, as well as the first Chilean attempt, in the war against the Confederation.
As a side note, it’s worth noting that all generous estimates give the “Peruvian expeditionary force” fighting alongside the Chileans the number of 600 men. Hardly, a force to reckon with.