In town after town occupied by El Salvador's guerrillas over the past few months the message has been the same, often scrawled in bright red letters on the villages' bullet-pocked walls: "We make war to conquer peace."

After more than two years of fighting, that is a seductive idea, and guerrilla strategy now is directed at making a single point.

"There are no possibilities of a solution in El Salvador if there is no participation by the Farabundo Marti National Liberation Front and the Revolutionary Democratic Front," as a rebel commander in Chalatenango province put it, speaking of the umbrella organizations for the rebel military forces and their political allies.

The insurgents are hammering the idea home by shows of coordinated military strength combined with subtle variations on their past practices that appear designed to win the trust of the population.

"The military advances have allowed us to gain important territories and more than gain territories, to gain populations," said Commander Bernardo Torres, a senior field officer of the hard-line communist guerrilla faction called the Popular Liberation Forces. "Our actions are attendant on a political objective. All our military conduct has its foundation in politics."

Economic sabotage that has crippled the country and created resentment against the rebels still goes on. But in areas recently fallen under their control the guerrillas let commerce continue almost normally.

When the 3,000 people of La Palma woke up on a recent Sunday morning they found their town full of guerrillas. The Marxist rebels had taken over the local elementary school and were using its mimeograph to crank out a propaganda newsletter. Others stood around on street corners passing the time with local boys their age or, if they were lucky, some of the local girls.

Tractor-trailer trucks and buses rolled through town unmolested to and from the nearby Honduran border.

In the afternoon there was a rebel military parade that youngsters watched with alternating amusement and awe. At night there was a dance, with the combatants of the Popular Liberation Forces boogeying like regular folks, except, of course, for the uniforms and rifles. Then, once again, in the hours just before dawn, they disappeared.

It is clear from talking to residents of such villages that the guerrillas do not enjoy the popular support that they often have claimed. The villagers tend to maintain a carefully studied neutrality. But if they do not support the rebels they are not hostile either, and that tolerance is all the guerrillas need, at least for now.

The point of this "political-cultural" exercise in La Palma, explained one eight-year veteran of the Popular Liberation Forces, now 25 years old, was "to let the people know what we are like. Before, they used to believe the government when it said we would kill everything down to the puppies."

In fact, the guerrillas are doing their best to avoid killing even government soldiers.

A prisoner policy initiated on a broad scale by the rebels last summer has been, in concrete terms, one of their most successful tactics.

As a government commander described it, "Their objective is to win a battle without a shot."

Although some officers are held prisoner indefinitely, the rebels hold enlisted men who surrender for very brief periods, sometimes only a matter of hours before turning them over to a local priest, or even their families.

"It takes longer to capture them than to free them," said one young rebel in La Palma. As a result, many small garrisons find it pointless to hold out against substantially superior numbers of rebels. When they lay down their guns, the rebels pick them up.

"Most of the weapons we have now are not recovered from dead or wounded," said Torres, "but from people who turned themselves in to us."

During the past month, the guerrillas claim to have captured almost 300 prisoners, the vast majority of whom have been released. At the same time they say they have collected almost 600 weapons.

Partly as a result, many government officers in areas where there are heavy guerrilla concentrations have quit staffing small garrisons altogether, and towns like La Palma in Chalatenango or Corinto in Morazan have become open cities for the rebels.

They are places where guerrilla fighters who have lived in the mountains under primitive conditions, in some cases for years, can get rest and recreation.

Meanwhile, government commanders concede, the prisoner policy is not only weakening the morale of some units, it is creating large numbers of soldiers who can no longer be trusted in combat. Although no military men were willing to release specific figures, they said some of the returned prisoners have had to be dismissed because of "brainwashing" or because their experience being captured "made too much of an impression." Most of the rest are kept away from the fighting and carefully watched.

"You have to have a certain reserve about these people," said one colonel, referring to the returned prisoners.

The effectiveness of these latest tactics has also had an impact on the rebel organization itself.

The factious revolutionary front has always had trouble working as a single body, and its five major groups remain seriously divided over many questions of ideology and long-term objectives. There is not even unanimity on the question of whether their goals can be met realistically through the "dialogue" for which they repeatedly call.

Members of the Popular Liberation Forces in La Palma said they believe that ultimately the government Army here must be defeated and, although they have endorsed the call for negotiations, they put little emphasis on dialogue in their public addresses except to make the point that the government has been rejecting the call.

At the other end of the guerrilla spectrum, the Armed Forces of National Resistance faction, with a more social democratic orientation, has for years advocated dialogue as the best way to resolve the country's problems.

At a guerrilla rally in the town of Corinto in Morazan last month the basic pitch of the Armed Forces of National Resistance political officer was that the fighting is only necessary because the U.S.-backed government is so steadfast in its refusal to talk.

The competition among the groups shows up even in their clandestine broadcasts. In a Radio Venceremos rundown of the guerrilla offensive that began in mid-January, Commander Joaquin Villalobos of the highly militaristic People's Revolutionary Army faction chronicled a string of successes in Morazan and Usulutan province by his units allied with troops from the Armed Forces of National Resistance, the traditional communist party and the Central American Revolutionary Workers Party.

Villalobos said not a word about Popular Liberation Forces actions in Chalatenango province.

But the prisoner policy, the low-key treatment of civilians and the importance of overall coordination are policies shared by all the guerrilla groups.

Since October the guerrillas have kept the Army guessing and almost constantly on the move from Morazan to Usulutan to Chalatenango. Since mid-January, building on their experience at the end of the year, they have stepped up the pace and intensity of the attacks.

The one major success claimed by the government in this period was to "clean out" guerrilla camps, including what has long been a major base at Guacamaya, in the middle of northern Morazan province. One of the three crack government battalions has been left in Morazan to patrol.

But Villalobos said derisively in his Feb. 11 broadcast, "For the enemy the government the Guacamaya camp is a myth. The elite troops and colonels are those who advanced and maneuvered with great fear, carrying out great encirclements of the hilltops and trenches, using intense fire against no one.

"We are no longer obligated to defend territory," said Villalobos. "We decide when to fight."