Hmmm.
I could see Chile getting dragged into this war, particularly if Peru is feeling its oats, or sufficiently paranoid. Check this guy out:
http://en.wikipedia.org/wiki/Juan_Velasco
It seems that in the 1970's, Peru was actively planning and preparing for a war of revenge upon Chile, and it was only averted by bad health and good luck.
If Velasco could carry a grudge that hard in 1975, what sort of grudges were popularly held by Peruvian leaders in the 1930's and 1940's?
Better yet, what if the Peruvians decide, rightly or wrongly, that Bolivia is receiving too much aid and comfort from Chile? What if they give Chile an ultimatum to stop trading with Bolivia?
On the part of Chile, who are they going to cheer for in a Bolivia/Peru war? Where does their advantage lay? If Bolivia goes to pieces, do they get to pick up the pieces? What if Peru overruns Bolivia or makes significant territorial gains.... what happens to Chile's strategic position? Are they willing to risk vulnerability?
Now, actually, if we go to Chile during this period, there's some pretty weird and interesting stuff going on. It turns out that Chile had its own National Socialist Party, modeled directly on and taking inspiration from Adolf Hitler himself. The Nazi movement had as many as 20,000 followers. Through the 30's, they drifted away from anti-semitism and adherence to Hitler and became more generically fascist. They seem to have peaked out in 1938, when they tried and failed to take power with a coup. The end result of failure being that a bunch of them got lined up against the wall and shot. Nevertheless, they lingered on through the 1940's.
Partly as a result of the attempted Nazi coup and subsequent massacre, a left wing progressive/technocrat named Pedro Aguirre Cerda won the Presidency and took power before dying of natural causes in 1941. He was succeeded by a caretaker named Mendez until 1942. In 1942
Now, here's something very interesting. Aguirre was a bit too left wing for the army, and so there was an abortive nonviolent coup in 1939, by a couple of Generals named Ibanez and Herrerra, using the Tacna Artillery Regiment in Santiago. Didn't go anywhere. The local officer in charge arrested Herrerra as soon as he showed up, Ibanez did an about face and nothing much happened. This was a scandal called the Ariostazo.
But here's where things get really interesting. General Herrera was pretty much a fascist. He wasn't part of the Chilean Nazi movement. Rather, he came to it from time spent in Italy and indoctrination with Italian fascism.
General Ibanez, on the other hand, was never a Nazi or a Fascist. What he was, was an actual bona fide dictator, between 1927 and 1931. He later served as an elected President from 1952 to 1958. Near as I can tell, he was a militaristic right wing shmuck. But here is what Wikipedia has to say about him, for that lovely significant period between 1938 and 1942:
Ibáñez decided to return to Chile, backed by a number of Nazi and fascist groups. His supporters, mainly the
Socialist Union (not to be confused with the Socialist Party) and the Nazi
National Socialist Movement, created the
Popular Freedom Alliance (
Alianza Popular Libertadora) and presented Ibáñez's candidacy in the
1938 elections. However, Chilean Nazis staged a coup against Alessandri before the elections. The government was able to defeat the rebels, who were arrested and executed. After this embarrassing incident, known as the
Seguro Obrero massacre, Ibáñez decided to abandon the presidential campaign. Unwilling to support his arch-rival Alessandri's candidate, right-winger
Gustavo Ross, Ibáñez declared his support for left-wing
Pedro Aguirre, who won the election.
However, in 1939, extreme right-wing General
Ariosto Herrera led a failed coup against Aguirre, the
Ariostazo. Herrera's purpose was to install Ibáñez as leader, but the latter denied any knowledge of the coup and was never charged with any crime.
In 1942, the small National Ibáñista Movement (
Movimiento Nacional Ibañista) declared Ibáñez their candidate for the presidency. Ibáñez quickly attracted the support of small Nazi and fascist parties. The turning point for his candidacy, however, came when, after some political infighting, the biggest right-wing parties,
Conservative and
Liberal, decided to support Ibáñez. In the
elections, Ibáñez won 44%, losing to left-winger
Juan Antonio Ríos, who had received the support of the anti-Ibáñez rightists led by Arturo Alessandri.
In 1944, Ibáñez was involved in yet another failed coup. Some Nazi soldiers and
carabineros (police), with the support of Argentine president
Juan Perón, tried to depose President Ríos and install Ibáñez. However, the plot was uncovered before it could take place. None of the coup leader, including
Ibáñez, were arrested or tried.
Well now, he's a very very bad boy, don't you think? I'm thinking that in 1938, 1939 and again in 1942, this Goose Stepper came very very close to power. It's possible that Bonifaz butterflies might well have been enough to push Ibanez over the edge, which means that we might have had pretty much an outright Nazi/Fascist style regime in Chile right around this time?
Significant? Maybe. Maybe not. Ibanez might have ruled democratically. Right. More to the point, its not at all clear that Ibanez would have gotten involved in Bonifaz style hugger-muggery. After all, Chile had won its war with Peru, it had taken Peruvian and Bolivian coastal provinces and still had them. It had nothing to gain by allying with Bolivia, or by picking a fight with Chile. Let's all remember that Francisco Franco was a fascist bastard who got in bed with Hitler and Mussolini, but he sat out WWII. Easy enough to imagine a fascist Chile sitting out an Andean war.
Anyway, back to the third little aspect of the Ariostaza - it involved an Artillery Brigade from or named after something called Tacna.
Where's Tacna? It's right next to Arica. Where are Tacna and Arica? Why, they're right on the border with Peru. These two areas were in constant dispute since the war of the Pacific. Y'see, during the war, Chile overran both cities. 1883, Chile promised to return the two cities after 10 years. Didn't happen. Chile kept them for the next fifty years. During this period, Chile began an intensive program of 'Chileanization' with the intent of keeping these territories. In 1929, Chile finally gave back Tacna, but kept Arica. Although Chile did keep Arica, Peru retained certain rights and privileges in that city, due to treaty.
So I assume that the Tacna Artillery Brigade was either originally based out of Tacna, and had been reassigned or redeployed. Or it had been named for the region as part of a local FU gesture to Peru. In any event, there's only about 10 years of depression and antagonism between 1929 and 1938-1942. The Chilean Fascist/Nazi's/Right wingers seem the type to nurse grudges and grievances a lot longer than that. So Tacna and Arica have a lot of potential to be flash points between Peru and Chile, particularly in an extreme Ibanez regime.
Now, it seems to me that an Ibanez/Fascist Chile is entirely possible in this timeline. But it has no vested interest in attacking Peru. On the other hand, we can guarantee that its relations with Peru are going to be pretty frakking poor. This is good for Bonifaz because it means that Peru has to tie down troops on the Chilean border as well as the Bolivian.
Poor relations with Peru means that if there is a Peru/Bolivia front, then Ibanez is probably going to support Bolivia. He has no love for Bolivia, but a lot of antagonism with Peru. A weaker Peru is in his interests. A strong Peru is not. A collapsed Bolivia with Peru directly or indirectly in control is totally not. So, initially, Chile sits out the Peru/Bolivia war, and just allows trade and traffic, arms and supplies to filter through to Bolivia. This doesn't help Peru/Chile relations. I could see situations going bad.
Meanwhile, Peru's nursing a grudge of its own, it lost whole provinces to the War in the Pacific in 1883, and we have to assume that there are large segments, particularly on the Peruvian right wing and military, who dearly would like to see those provinces back. On the other hand, Peru is also fighting a one, or even two front war, with Ecuador and maybe Bolivia. I don't think that Peru would be enthusiastic about expanding that to a possible three front war. Still, lets assume that the Bolivia campaign happens, and it goes really well, or Chilean meddling becomes intolerable... the Peruvians might go for it.