Peru's dirty war was long and weird and ugly. Sendero was always a rather small group but also stark raving mad. The military response to Sendero was far too often the predictable brutal massacre of innocent peasants -- by which I mean that groups of people were chopped to pieces and their body parts stacked like cordwood as a "warning." Ordinary poor people were caught in the middle: if not killed by Senderistas as "collaborators" then at least as likely to be killed by gung-ho militarists as "insurgents." This dragged on for two decades, although the US press predictably only ever pointed its idiotic finger at Sendero.
But the overall role of the military in Peruvian society may not be entirely rightwing: it is sometimes claimed that the Peruvian military includes a significant populist group, although I do not know how to evaluate this claim.
Anyway, the allegations against Humala did not hurt him electorally in the regions of the worst military abuses -- but that may not mean the allegations are false:
Voting for the Accused
Ángel Páez
... The memory of the Accomarca massacre -- one of the worst in the 1980-2000 "dirty war" against the Sendero Luminoso (Shining Path) Maoist guerrillas -- is still fresh. Yet in the first election round held Apr. 9, a majority of the townspeople (71.8 percent) voted for Humala, despite investigations into his alleged abuses during the counter-insurgency struggle ... In the village of Umasi, army patrols killed 41 people in 1983. No one has been brought to justice. There, Humala won 68.9 percent of the vote ... "The troops that went up against Shining Path members were almost entirely comprised of young men recruited from Ayacucho villages," explained Caballero. "Ollanta Humala's party has the support of thousands of reservists who fought against the Shining Path. They are the ones campaigning for Humala in the former war zones" ... "The judge who investigated numerous crimes committed by members of Counterinsurgency Base 313, in which Humala was deployed, had the case shelved due to lack of evidence, manipulated by the accused military officers, who had many resources," said Macher ...
http://www.ipsnews.net/print.asp?idnews=33347