Why Father Poncel joined El Salvador's guerrilla movement

He has a few days' growth of beard. His clothes are worn and hang on his gaunt frame. Many of his teeth are missing. To look at him is to be deceived.

He is one of the most well-known guerrilla figures in El Salvador. For three years Rogelio Poncel, a Roman Catholic priest from Belgium, has been in these hills.

His presence here embodies the ideological split that has torn the Catholic church in Latin America asunder.

''I am not an intellectual,'' the soft-spoken prelate says outside his bamboo house in a guerrilla base camp. ''I learn my theology from the poor.''

Poncel was once one of the firebrand activist priests who fueled the hopes and ambitions of the underground union and political movements here. He came to El Salvador in 1970. By the end of the decade he was intimately involved with leftist movements, many of which were armed.

Poncel was a vocal critic of those in the church who refused to condemn the social injustices here. He also attacked church figures, including Roman Catholic Archbishop Oscar Arnulfo Romero, whom he considered too restrained in their criticism of the Salvadorean government.

''He was,'' a colleague says, ''one who had impatience and even disgust for those of us who tried to work within the existing order.''

By 1980 Poncel was in hiding. He slept in a different location each night and varied his schedule daily. Many of those he worked with had fled to form fledgling guerrilla bands or had been killed by the government security forces.

A recently published photo history of El Salvador shows Poncel some 60 pounds heavier, crying as he leads a mass for six slain opposition leaders.

''On Christmas Day three years ago,'' Poncel says, ''after a bomb exploded in our rectory, I realized I had only one option left if I wanted to stay in El Salvador. I traveled that day to northern Morazan.''

Poncel has since served as a pastoral and ideological adviser for the People's Revolutionary Army (ERP), one of five groups that make up the Farabundo Marti National Liberation Front (FMLN). He now runs the propaganda arm of the ERP.

''Before I joined the guerrillas,'' Poncel says, ''I was a mediocre priest. I told my congregation to give their lives for Jesus, but I never knew what those words meant.

''Since coming to these hills,'' he says, ''I realize what Christian sacrifice means. I realize the cost of fighting the system of exploitation that Christ fought.''

Despite his efforts to disown his intellectual heritage, Poncel admits to being heavily influenced by liberation theologians.

''Their work,'' he says,''was a revelation.''

Liberation theology, a term coined some 20 years ago by Peruvian priest Gustavo Gutierrez, has become the driving ideological force behind most armed leftist movements in the region, as well as a liberal faction of the Catholic church known as the ''popular church.''

Liberation theology uses Marxist analysis to explain social ills in Latin America. It claims that the message of the Bible is a call of liberation for the poor. This ideological movement justifies armed revolt and speaks of the ''new Christian society'' that will be obtainable with the removal of the old order.

The vision that fuels the guerrilla ideology is a mixture of this utopianistic theology, Marx, and Lenin.

Poncel, like most guerrilla leaders, is vague about the specifics of how the new society will be shaped. He prefers to deal in abstract concepts, calling for justice, a government of the poor, and an equal distribution of wealth.

Liberation theology, unlike earlier Marxist movements in Mexico or Europe, has appropriated Christian symbols rather than rejected religion.

In a region where more than 90 percent of the people are at least nominally Catholic, this effort to integrate a revolutionary agenda with what liberation theologians define as the ''authentic gospel'' appears to be proving highly successful.

Poncel claims the guerrilla fighters and commanders are ''more Christian'' than he is. ''They live as one and lay down their lives each day for their brothers and sisters. I, as one who does not fight, am humbled by this.''

For Poncel the message of the Bible is in accord with Marxism. It is a message, he claims, that calls the oppressed to overthrow their oppressors.

''I worked with a nun, Sylvia, when I was in the capital,'' he says, ''and she was opposed to violence. Finally the time came when she knew there was no other way. She died in Santa Ana with a pistol in her hand. This is conversion for the poor.''

For Poncel, there is no contradiction between the roles of priest and fighter.

He does not carry weapons - but only because he has a hard time explaining such action to poor peasants he speaks with in the countryside. ''I have known priests here to go into combat,'' Poncel says, ''and I admire them for this.''

''The Bible's ideal was nonviolence,'' Poncel says, ''but Jesus knew there were times when men had to fight. The important thing is that we do not fight with hatred. We received captured soldiers as our friends.

''What people do not understand is that our call is more difficult than Marxism,'' Poncel says. ''We are fighting to create a society of brothers and sisters, a society based on Christian love without separation. We are fighting for a new society built by God's power through our hands.''