The strongest group in the Salvadorean guerrilla movement, in a severe policy shift, is pressuring civilians in northern Morazan Province either to join the rebels or leave this region.
This change in strategy - which occurred after a shakeup in the overall rebel command about 21/2 months ago - has spurred some 2,000 people to flee northern Morazan over several weeks, police officials say. It has also provoked intense resentment among residents who remain here.
Specifically, the rebels of the People's Revolutionary Army (ERP) are pressuring Morazan residents to:
* Collectivize individual plots of land in order to feed the rebel army better.
* Send their children (some as young as age 7) to guerrilla schools, where they will learn rebel ideology and how to use weapons.
* Join labor gangs to do road work, carry wounded rebel soldiers, and contribute to the guerrilla infrastructure. Residents who refuse to help voluntarily are forced to assist the rebels.
* Join the insurgent army. If young men do not join voluntarily, they are forced into rebel ranks.
Rebels here contend that these procedures are justified because of what they call an increasing possibility of United States intervention in the Salvadorean civil war. The ERP guerrillas say the first steps of US intervention will consist of air strikes on rebel-held territories.
''We have to prepare the population for intervention,'' says an unshaven ERP rebel, ''and this requires the organization of the people to move rapidly when the massive air strikes begin. If we do not incorporate the people into our structure, we won't know what to do with them or their bones.''
The ERP also admits that the new procedures dovetail with its political objectives.
''If people continue to feel they can be neutral in this war, they will be killed,'' says a guerrilla. He adds, ''They must now take sides in the conflict. The dynamics of the war have changed.''
That the ERP is able to pressure civilians this way signals that it is growing even stronger. The official government is less and less able to maintain control in the province. The rebels are in effect creating their own government. Some observers think the strategy shift in Morazan shows that ERP leader Joaquin Villalobos, commander in chief of all Salvadorean rebel forces, is consolidating his own power, too.
Civilians who have been confronted with the guerrillas' pressure to enter the rebel infrastructure are embittered.
''Suddenly we are being told what to grow,'' says Juan Jose Espinales, a peasant farmer who abandoned his plot of land last month and now lives with his family in a tiny cardboard shack on a dirt lane outside the provincial capital of San Francisco Gotera. ''We must work for them, and if we do not we are taken prisoner. Our women are taken to cook in their camps and our children are taken to fight. Many people have now turned against the guerrillas.''
''One reason we left is because the guerrillas want to take our children, and that's bad if you are a widow,'' says Caterina Argueta Dias. Like many other people who have fled the zone, she said that increased aerial attacks by the government's air force also were a factor in her departure. ''They take the children far away, it is far from Cacaopera. I don't know what they want to do with these children. They want to have them there studying, and for what?''
The quiet mountain village of Cacaopera, located in the volatile no man's land between the rebel and government armies, was one of the hardest hit by the new guerrilla procedures. Some seven weeks ago, the rebels entered the town at dawn and forced the townspeople to gather on the uneven cobblestone plaza in front of the small Spanish-mission Roman Catholic Church.
''They separated the people into two groups,'' says Philomena Sasiaza emotionally. ''One group was for old people and women, the other was for young men. Then they told us they were taking our boys away to speak with them.''
Sasiaza watched as her two sons were led away in a column by the guerrillas. Some 100 young men and boys, nearly the entirety of the town's youth, were taken by the rebels. They have not been heard from since.
Relatives were twice told by guerrillas passing through the town they could visit their loved ones if they traveled to the small village of El Colon. Timid groups of women and older men twice made the two-hour journey by foot, carrying food for their kidnapped relatives. Each time they arrived at El Colon they were turned back by rebels in the village.
''We were told that our children were not there, that they were far away,'' says Sasiaza, ''and we would not be allowed to visit them.''
Two weeks after the abductions a guerrilla patrol returned to Cacaopera at night and took 10 prominent local citizens, including the mayor, town clerk, and two unarmed municipal policemen.
''Three guerrillas came to our house at 10 at night,'' said Orbelina Ramos de Herrera, whose husband is the former Christian Democratic mayor for the town. ''They ordered my husband to get dressed and they took him to the mayor's office with the other men. All of them were held there overnight. They were marched out of town at about five in the morning with their thumbs tied behind their backs. We were not allowed to speak with them or give them something to eat for breakfast.''
The townspeople were once again called by the rebels to the Central Plaza at dawn. When they arrived, they saw the mayor's office in flames. The guerrillas had burned the town records.
''The guerrillas told us at the meeting that the 10 men were being investigated,'' says Herrera, ''but they didn't say why.''
Rebels say they take civilians before guerrilla courts when they are suspected of committing ''crimes against the people.''
''Punishment,'' a guerrilla says, ''can include manual labor, incarceration for a few days in a hole in the ground, or if the offense is serious, execution.''
Rebels often hold wealthier citizens from a town for ransom.
The insurgent fighters handed out two-sided broadsheets during their last town gathering entitled: ''Duarte Doesn't Represent the People.'' They pasted the broadsheets around the town and once again left.
''We immediately tore the propaganda off the walls and most burned the literature they gave us,'' says Alvina Pereda, ''because if the armed forces saw us with it, they would accuse us of being spies.''
One woman who saved the dittoed paper carefully unfolded it for inspection. The paper, illustrated with a crude drawing of planes and helicopters attacking a village, says that ''Duarte is an instrument for US military intervention in El Salvador.''
''I went through this four years ago when the guerrillas took my son,'' says Soltera Martinez de Herrera. ''I worried day and night and then one day a guerrilla came to my house to tell me not to worry about my son any more because he was dead.''