WITHIN the past several months, Peru's guerrilla insurgency, Sendero Luminoso (Shining Path), has assassinated two Polish priests, an Australian nun, a Soviet technician, a Colombian relief official and a Canadian relief official, three Japanese engineers, an Italian priest, and hundreds of unarmed Peruvian citizens. Sendero Luminoso is the cruelest guerrilla movement in the history of Latin America, and the elected civilian government of Peru desperately needs help to counter Sendero's growing strength.Tragically, grievous human rights abuses by the Peruvian armed forces and police themselves make it difficult for foreign governments to support them in the war against Sendero. While the international community ponders the ugly options of either standing by while a vicious insurgency gains in force or aiding an almost comparably abusive Army, Peru's innocent civilians suffer and the country's social and political institutions totter on the brink of collapse. Sendero Luminoso was launched in 1980 by a group of university radicals who espouse a bizarre ideology which embraces China's "Gang of Four" and denounces support for human rights as a "bourgeois" conceit. Sendero's hatred of "revisionist" institutions leads them to assassinate government officials, leaders of leftist grass-roots organizations, and even church authorities. Their extreme xenophobia is expressed in targeting and execution of dozens of foreign missionaries and development specialists workin g in impoverished rural areas. With its rigidly organized Maoist cadres and violent abuses against the "masses" it claims to serve, Sendero bears some resemblance to Cambodia's Khmer Rouge. The group's rapid growth over the past decade has been financed by its strategic alliance with cocaine producers in the Upper Huallaga Valley. Some of Sendero's civilian followers are coerced by such terror tactics as public "trials" and executions of thousands of community leaders, mayors, clergy, and teachers. Ironically, the very forces that are engaged in combat with Sendero are driving people into its arms. Villagers who have witnessed uniformed soldiers shooting and hacking civilians to death, and families whose sons and brothers have been abducted and secretly murdered, have come to hate the state and are drawn to Sendero's violent cause. The Army's counterinsurgency tactics were vividly demonstrated last month when 50 soldiers entered a peasant community in Huancavelica, threatening to kill the residents if they did not give them food and livestock. Fourteen people (including seven children) were abducted by the soldiers, and cattle, sheep, and alpacas were stolen from the village. Body parts of some of the 14 were found a week later in an abandoned mine. They had been dynamited to prevent identification. Massacres such as the one in Huancavelica are common, and the civilian authorities have had virtually no success in reining in, let alone prosecuting, those military officers responsible. A government prosecutor attempting to investigate the Army's massacre of 28 civilians in 1988 was literally run out of Peru on threat of death, and nine of 10 witnesses who dared to testify to civilian authorities were murdered or "disappeared." Political violence has claimed the lives of more than 17,000 Peruvians in the past decade (most of them noncombatants), and no end is in sight. Most were killed by Sendero, but the armed forces do not lag far behind. This year, 3,000 more Peruvians are expected to die in politically-related violence; Sendero Luminoso is growing; foreign aid workers are fleeing Sendero-controlled areas; poverty is deepening; and a nationwide cholera epidemic has infected thousands. Most Peruvians would agree that the very survival of their country is at stake. The world stood by and watched when Pol Pot reigned over Cambodia's killing fields, slaughtering and starving millions. Sendero Luminoso's maniacal ideology and appalling practices suggest that Peru could face a similar future if the group is not stopped. Yet, international assistance to the counterinsurgency as it is currently prosecuted is likely to enhance Sendero's strength, not diminish it, as Sendero plays on "anti-Yanqui" sentiment. Increased military operations without significant human rights re forms mean more Army massacres, more disappearances, and more Sendero supporters. The government of Peru should explore means of engaging such organizations as the Organization of American States and the United Nations in monitoring and protecting human rights and bringing Peru's brutal conflict to an end. But the Peruvian armed forces and police must also make dramatic changes in their practices so as to be worthy of international assistance against Sendero Luminoso. If they do not change their ways, Peru will stand alone against an insurgency of incalculable brutality.