Rebels Thrive in Rural El Salvador. CULTIVATING PEASANT SUPPORT.

JUST hours after leading a rebel attack on a Salvadoran Army unit in the hills above this village, Comandante ``Antolin'' strolls into town as if returning from a day at the office. The hills are still smoldering from the Army's barrage of helicopter gunfire. Children continue gathering the fallen shell casings, whistling into them like empty Coke bottles. And fresh Army troops are expected to pass by the settlement in a few hours.

But Antolin, the top regional commander of the leftist Farabundo Mart'i National Liberation Front (FMLN) - feels safe and sound in Santa Marta.

Freshly shaven and sporting a yellow Ralph Lauren Polo shirt, the 37-year-old guerrilla leader settles in for a long candlelit interview. He doesn't mind being in plain view of the villagers who have resettled here after fleeing Army bombing raids in 1981.

``I've been able to show these people that I'm not their enemy,'' says Antol'in, explaining how he can venture here without bodyguards - and how he thinks the FMLN can gain the upper hand in its nine-year war against the United States-funded Army.

``The force of the FMLN resides in the people,'' says the urbane revolutionary, a university graduate who first became involved in clandestine leftist groups 21 years ago. He notes that the guerrillas have reestablished themselves in the Cabanas Department (province) over the past year and a half. ``If the revolutionary message reaches people's hearts because it describes a situation that they feel and experience, then there is no power in the world that can stop them.''

So far, not even the 60,000-strong Salvadoran Army - flush with over $850 million in US military aid over the past eight years - has been able to squelch the 7,000-member insurgency.

The Marxist-inspired rebels, who are fighting to redistribute the nation's wealth, have strong roots in communities like Santa Marta that have been battered by poverty and repression. They control 29 of the country's 262 municipalities, and have expanded their presence to all of El Salvador's 13 departments - including the capital.

But the FMLN is being forced to play politics. While considered the best-trained guerrilla army in Latin America, the FMLN does not have the force to turn the tide of war in its favor. Its international backers are tired of the war and are pushing for a negotiated end. So are more than 60 percent of all Salvadorans, according to a recent opinion poll.

``We need international support and we need the internal masses,'' acknowledges Antolin. ``If the people's strongest desire is for peace, then we must show our real political will and win the sympathy of the masses.''

Pushed to be more flexible by this collective longing for peace, the FMLN is planning to launch a second ``peace proposal'' sometime before newly elected right-wing President Alfredo Cristiani takes office on June 1.

The new initiative, Antol'in says, will deepen the concessions made in the rebels' January proposal, which called for a six-month delay of the March 19 election while the two sides negotiated an end to the war. Now that the election has passed, he says, the new plan will deal ``concretely with the social-economic model that could be implemented.''

Antol'in doesn't harbor any illusions of an imminent end to the war.

The proposals, rather, seem designed to wrest the public-relations initiative away from Mr. Cristiani's ultraconservative Nationalist Republican Alliance (ARENA). They force ARENA and the Army ``to unmask themselves'' as the true warmongers, says Antol'in. And, by taking up the banner of peace, the FMLN hopes to cultivate more civilian support, as it has in Santa Marta.

Such guerrilla bastions make the Army's job tougher. Earlier that day, at an outpost two miles above this village, a frustrated Army officer and 30 soldiers were catching their breath after the 45-minute clash with Antolin's troops. ``They were shooting from the houses,'' complained the shaken officer. ``Here we are guarding these people and they shoot at us....''

Looking down the valley toward Santa Marta he added angrily: ``It's a town of subversives.''

His charge carries a grain of truth: For, in Santa Marta, signs of sympathy for the guerrillas - like the remnants of recent fighting - are inescapable.

In the mornings, as sunlight slants through the smoke of breakfast campfires, villagers listen openly to the music and news of clandestine station Radio Farabundo Marti, until it is overtaken by another, Radio Venceremos.

In the afternoons, if enough church-supplied materials have been allowed through by the local Army commander, villagers work on communal farming or construction projects organized by the town's 16-member directorate - and protected by the FMLN.

The town's support for the FMLN becomes even clearer at dusk: Dozens of guerrillas filter into the town plaza, elusive shadows in the enveloping darkness. Clusters of villagers gather around each combatant, pressing in to hear the latest news. A 17-year-old in a maroon beret boasts about the eight Army casualties. A small 13-year-old rebel holds court with over a dozen children as if he were the hero of a junior high-school basketball game.

But Santa Marta didn't become a guerrilla oasis overnight.

It began with a mix of poverty, neglect, and repression fostered by 50 years of military rule. Then, just as the guerrillas began to build their force in the area in March 1981, the Army let loose three days of bombing that forced several thousand peasants to flee. Three dozen villagers - many of them children - were killed on their way to the Mesa Grande refugee camp in Honduras.

Incensed by the violence and influenced by FMLN promises to spread the wealth, many came back to join los muchachos (the boys) as the rebels are fondly known here.

``There were no options left for us,'' says a robust, 35-year-old woman, who helped cook for the guerrillas in 1981. Her two sons joined the rebels and were killed in combat - both at the age of 17.

Much to the Army's dismay, the rest of the villagers returned in two waves in October 1987 and November 1988, taking advantage of a political opening provided by the August 1987 Central American peace accord. Today, over 2,000 peasants live here.

Despite FMLN and ARENA promises of negotiations, Santa Marta residents fear the war will intensify. ``One soldier told me, `Just wait until ARENA wins, then we will put a bomb in every one of your houses,''' says Candida Recinos, a member of the village directorate.

Such warnings evoke bitter memories of earlier bombings.

``We certainly had a little scare,'' says Alicia Garc'ia, her eyes filling with tears as she ponders the past - and the future. ``Now we're just waiting here with our arms folded, wondering what they [the Armed Forces] are thinking. We can never know what they are thinking.''