The young seminarian had just concluded a meeting with 70 peasant families, assuring them that the bishop of this Amazon diocese is doing everything possible to keep them from being forced off their land. He was walking down a jungle road, chatting with parishioners, when the military police arrived -- and the trouble began.

After dispersing the peasants at gunpoint, three military police officers forced 24-year-old Eduardo Campos Pedroso into their car, where he was kicked, punched and beaten unconscious with butts of rifles and pistols. When Pedroso came to, he was forced to eat a roll of toilet paper, then dumped without charges into a jail cell and held for 48 hours.

For more than a decade, incidents such as the one that befell Pedroso here on Jan. 6 have been frequent in Brazil, the world's largest Roman Catholic country. Brazil's authoritarian military government is engaged in a war of attrition with the Catholic Church, and despite promises of "decompression," the bitter conflict shows no signs of letting up.

The source of the dispute is the government's suspicion of the "theology of liberation," a controversial blend of Christian dogma and social activism endorsed by the Brazilian church hierarchy. Thousands of Brazilian and foreign priets, nuns and lay workers are attached to more than 50,000 "ecclesiastical base communities" applying that theology among the nation's millions of urban and rural poor.

Such attempts to turn the church into a force for social change is one of the subjects Pope John Paul II will have to deal with at a conference of Latin American bishops scheduled to begin Sunday at Puebla, Mexico.

Church leaders here say they are merely following guidelines laid down at the Second Vatican Council and the last conference of Latin American bishops at Medellin, Colombia, in 1968. But to Brazil's military men, the church's increasingly activist stance is a threat to the status quo. In the words of one general here, the activism "reeks of Marxism."

The result has been a nationwide campaign of violence and intimidation in which dozens of clerics have been killed, tortured, kidnaped, jailed and deported in recent years.

Perhaps nowhere is the Churchstate conflict more acute than in remote and backward areas such as the Amazon. Gen. Euclydes Figueiredo, commander of the Amazon military region and brother of Brazilian President-elect Joao Baptista Figueiredo, recently charged, for example, that the Amazon church harbors and protects "subversive" and "communist" priests who "use the gospel and the image of Christ as camouflage and the cassock as a shield."

Figueiredo also accused the church of undertaking a campaign to "brainwash" the Amazon populace. "They act insidiously," he said, "injecting their poison in small doses, slowly and subliminally, in literacy courses, in meetings of base communities, through sermons at mass, in speeches, in parish bulletins and even in hymns."

Figueiredo's criticism drew a strong rebuke from Cardinal Paulo Evaristo Arns of Sao Paulo, the Brazilian church's leading spokesman. "Gen. Figueiredo is hundreds of miles out of his area of competence," the cardinal said, "and talks as if the church arrested on charges of inciting peasants to rebellion.

For Dom Alano Pena, bishop of Maraba, friction generated by the rift between church and state is a daily fact of life. Since assuming office three years ago, Bishop Pena has seen a mass interrupted by soldiers cradling machine guns, had his office searched and personal belongings seized by military police and been were at the service of the armed forces and not at the service of God and His people."

"Through our work at the community level, we have sought to make the peasant and the worker aware that they have certain basic rights and that they are entitled to exercise those rights," the bishop explained. "To the military, that is the same thing as subversion."

Among activities that have aroused the ire of local military authorities are literacy classes, voter education projects, construction of schools and community centers, legal advice and distribution of medication. In each case, the projects have been carried out by lay-led "base communities" advised and supported by the church.

Many programs have risen in response to the lack of government services. Pregnant peasant women have been known to walk 125 miles to give birth at a clinic run by Carmelite nuns at a jungle settlement north of here -- the only one of its kind in the region.

But, says Father Roberto de Valicount; a French priest arrested and tortured here in 1972, "all it takes to upset things is a denunciation by a rich rancher or some pharmacist who's charging 10 times the legal price for medicine. Then the government is only too happy to lower the boom on us."

According to Bishop Pena, harassment against him and the nine priests, 26 nuns and seven lay workers under him has stepped up since a November 1976 incident in which settlers south of here resisted a government force sent to evict them from their land, killing two military policemen. Though charges against Bishop Pena have now been dropped, another bishop and a priest remain charged in the case.

Immediately following the clash, an Italian priest at a parish just north of here was deported, and in May 1977, two American nuns were called to military headquarters here for questioning and threatened with expulsion. Since then, the bishop says, his vicar has been tortured by police and parishioners who allowed mass to be said in their homes have been beaten and threatened with imprisonment.

Bishop Pena also claims that church activities are under constant surveillance by government intelligence agents -- a charge that has been repeated by the National Conference of Brazilian Bishops. According to the conference's head bishop, Ivo Lorscheiter, security police all over Brazil have been preparing dossiers on the clergy.

"Instilling fear through violence has become part of the habitual behavior of the military forces here," Bishop Pena added. "One year ago, the commander of the local garrison and the major in charge of security sat right where you are and told me it would be good for my health if I left Maraba."

Similar warnings were issued in 1976 to Rudolfo Lukenbein and Joao Bosco Burnier, priests in the diocese of Sao Felix do Araguaia south of here. Both were shot dead soon after: Father Lukenbein while defending Indians from vigilantes and Father Burnier inside a police station where he had gone after hearing the screams of two women parishioners.

The clerical and lay "pastoral agents" attached to the base communities in Maraba, though, make it clear that they plan to continue their work and that their ultimate goal is to bring about change in a society they see as riddled by injustice and exploitation. They deny, however, all charges of communist inspiration or infiltration.

"I am a Christian doing a Christian's work,7" says Colemar Pereira, a 28-year-old lay worker assigned to a jungle village 85 miles north of here. "That means I am motivated not by a particular ideology but by my faith."