Since middle school, I have came across the Paraguayan War (1864-1870) several times in my history textbooks. I never liked this subject; actually, I'm used to simply memorize some keywords as Solano López, La Plata River, the Triple Alliance, and Genocide.
This year, however, I began to think about what I was reading. And a particular point of the textbooks called my attention. Please, read this paragraph:
"British commerce did not hide its concern, not only because this last bastion of national resistance in the heart of the continent seemed invulnerable, but also and especially because of the dangerous example set to its neighbors by Paraguayan obstinacy. Latin America's most progressive country was building its future without foreign investment, without British bank loans, and without the blessings of free trade."
This comes from "Open Veins of Latin America", written by the journalist Eduardo Galeano, published (in English) in 1973. The excerpt sums up the predominant view of Brazilian historiography, that the British imperialism played a central role in the Paraguayan War.
The Brazilian textbooks presented to High School students are stuck with this view. They don't offer other versions or explore divergent opinions. That's why I'm coming here. I want to know about the other side. What does modern anglophone historiography says about the Paraguayan War?
Was Latin America a relevant matter for the British during the mid-nineteenth century? Did the British have serious interests in La Plata River? Did the British appreciate the destruction of Paraguay? Was the War good for the UK? How did the UK react to the conflict in its first years? How were the relations between the UK and the South American countries back then?
I hope you can answer some of these questions. And I want to make clear that I'm currently taking the second year of High School. So, when I say "Brazilian historiography" I'm referring to what I have read so far, what the teachers have told me. Perhaps in Brazilian universities the situation is different. I don't know.
I am in no position to answer some of this questions, but I will do my best to answer a few of them.
There is different views about how the conflict started:
(a)the traditional Brazilian view, Solano Lopez was a megalomaniac dictator who started the whole thing by aggression against his neighbours. It was the main view in Brazil until the 1960's, it emphasized "national values" about patriotism and "national military heroes";
(b)the traditional Paraguayan view, their neighbours were the aggressors and they fought a defensive war for their survival. It was also used in Paraguay for propaganda purposes, specially in the Strossner dictatorship;
(c)the Latin American leftist view: basically you described in your question. Paraguay refused integration with the capitalist system, United Kingdom feared South American countries would follow Paraguay and then manipulated them in going to war, which benefited the British Empire by destroying an economic adversary. In my own point of view this version is basically propaganda, about a mythic superpowerful Paraguay and British Emperialist boogeymen.
At the time, the British and Brazilian empires were not in good terms; in 1863 there was a major diplomatic incident (known in Brazil as "Questão Cristie" ) between the two counties, when a merchant ship's (HMS Prince of Walles) cargo was stolen in Brazilian waters; the British ambassador was recalled and the British Empire threatened to blockade Rio de Janeiro! Brazil would pay for the cargo and apologise to come back to friendly therms with the British in 1865, one year after the start of the war;
(d)the recent academic view: its more complicated and more detailed then the rest, and its based on actual documentation. Basically, Paraguay was a regional power, but could not match the United Kingdom; It was landlocked and needed badly a maritime port; it had local alliances with the Blanco Party in Uruguay and with the Argentinian provinces of Corrientes and Entre Rios.
Brazil had some history of military intervention in Uruguay, and did it again in 1864. The main reasons for this intervention was to show "military power" to the unfriendly Great Britain and to support some southern Brazilian farmers who had disputes with Uruguay. It supported the Colorado Party, then in civil war with the Blancos. Paraguay threatened war with Brazil for this, but Brazil ignored them. Paraguay then invaded Mato Grosso state, and forbid Brazilian navigation in their rivers.
Paraguay President Solano Lopez then asked free transit for his troops in Argentina (to support his allies in Uruguay), which was refused. Solano Lopez thought Corrientes and Entre Rios would at best join him on war against Brazil, or at worst remain neutral. He then proceeded to invade those Argentinian provinces to help his Uruguayan allies. When he did invade, public perception within Argentina changed completely and they signed an alliance with Brazil. In that alliance, between Brazil, Argentina and the Colorado Party in Uruguay, they agreed to only stop war when all the three counties agreed.
Paraguay lost in several major battles like Riachuelo and Tuiuty, despite having a larger army than all the other countries combined in the beginning of the war. Paraguay tried to negotiate a separate peace with Argentina, but Argentina was bound up with the alliance with Brazil.
Brazil asked for Solano Lopez to step down as a condition to Paraguay surrender. Solano Lopez refused and Paraguay was utterly devastated.
I can provide sources in portuguese, if you need.
There is some very good documentaries in portuguese about the causes and events in the Paraguayan War.
Here is an answer to a similar question that I answered a while ago which I think will be interesting for you. In short, yes and no...the British were involved in South America to some extent, though the dynamics of that involvement were not as forceful as Galeano asserts. I wish I could answer how the British public reacted to the war, but that lies outside my field of expertise. That might be an extremely interesting question to ask as a separate AskHistorians thread: "How did the British public react to the Paraguayan War?"
In terms of historiography, in reality, there is very little work being done on the Paraguayan War in the Anglophone academic world. Even the state-formation thesis that I rely on heavily in the answer that I linked above and this one in which I discuss some historiography of the causes really needs an overhaul to include more social and subaltern perspectives. Right now, I can think of maybe 4 historians who have published works on the Paraguayan War in the last 20 years, and those that have been published focus on the political and military components of the war.