GENERAL LUNA, PHILIPPINES -- For two days, the communist guerrillas waited patiently in the thick forest along a desolate stretch of road in Quezon Province, 110 miles southeast of Manila.

When the Army convoy finally rumbled around a bend in the gravel road, the trap was sprung.

A homemade land mine detonated by a guerrilla blasted the lead vehicle, an armored personnel carrier, into a deep ravine. Another mine wrecked a truck packed with soldiers.

Two dozen guerrillas, most of them peasants in their teens, raked the stunned government troops with automatic rifle fire and hand grenades. When the firing stopped, the guerrillas had killed 19 soldiers and wounded seven, without suffering a casualty.

Rebel medics moved through the wreckage of the convoy, dressing soldiers' wounds and explaining why they were fighting the government. Other guerrillas collected booty: a powerful field radio and 27 automatic rifles, enough to arm a rebel platoon.

That March 17 ambush near this town, described recently by the guerrillas who carried it out and corroborated in Philippine Army accounts, typifies the tactics the communist New People's Army is using to sap the strength and morale of President Corazon Aquino's Army.

The guerrillas remain outmanned and outgunned, but they have improved their situation steadily in recent years. Although lacking heavy weapons capable of stopping government tanks and armored personnel carriers, the guerrillas have developed sophisticated land mines in the past two years. The explosives have been used with deadly effectiveness since a cease-fire collapsed in February.

Army and guerrilla leaders agree that the rebel army of 24,000 soldiers remains far from a military victory. But 18 months after Aquino replaced Ferdinand Marcos' authoritarian government with democratic rule, the 18-year guerrilla war shows no sign of abating.

In finding reasons for the guerrillas' ability to counterpunch successfully against a 240,000-man government Army that is receiving $50 million in U.S. aid this year, foreign diplomats and military analysts note the contrasts in motivation, morale and leadership between the government and rebel forces.

Those contrasts were underscored to a reporter who spent six days with communist guerrillas of the New People's Army in southern Quezon Province's Bondoc Peninsula. The guerrillas appeared to be highly motivated and thoroughly indoctrinated, in contrast to most government soldiers, who enlist because military service is often the only alternative to unemployment and hunger.

Aquino has increased salaries and improved logistics, but ill-fed and ill-trained soldiers continue to fare poorly in combat against the determined guerrillas.

Defense Secretary Rafael Ileto has estimated that it will take more than a decade to whip the Army into the desired fighting shape.

The communists, in the meantime, continue to tap a pool of talented, disaffected young people.

Lisa and Aries, guerrillas who said they participated in the March 17 ambush, are young people who could choose their futures -- and chose the guerrillas.

Aries, the 19-year-old son of a poor lumberyard laborer, was working part-time while studying agriculture at the University of the Philippines. Shortly after the cease-fire between the government and guerrillas collapsed Feb. 8, he joined the main guerrilla combat unit in southern Quezon.

He tasted combat for the first time in the March ambush. "It was good," he said with fervor.

Lisa, 28, is a product of an exclusive Catholic high school and university in Manila, and taught for a while at her former high school. After several years of activist legal work, she went underground in February and joined the Quezon guerrilla unit.

"I think the legal struggle is no longer effective; only armed struggle can change our situation and free us from U.S. control," she said in an interview in a guerrilla camp on the Bondoc Peninsula.

Lisa accompanied the group of about 50 guerrillas to the ambush site in mid-March, assigned to assist two guerrilla doctors.

"It was my first ambush, my first time to see dead bodies," she said. "I was surprised . . . to see our fighters bandaging the wounded soldiers."

Her most enduring memory of the day, she said, was the welcome given the guerrillas, after the action, by sympathetic peasants in a nearby village. The villagers gave them coconut juice, jugs of water, platters of corn on the cob and peanuts, she said.

Governmental soldiers seldom encounter this kind of welcome. Instead, their lives alternate between the boredom of camp and the occasional terror of patrols through the mountainous jungle.

The gulf between the lives of enlisted men and senior military officers in the government's Army is wide: the officers frequently live in comfortable houses in cities, while enlisted men struggle to eat on a daily food allowance of 12 pesos, or about 60 cents.

By contrast, in the southern Quezon guerrilla camps, Ka (Comrade) Elmer, a senior Communist Party official for the region who was once a University of the Philippines physics professor, eats and sleeps on wooden planks alongside the peasant guerrillas. He also takes his turn washing dishes.

Leaders and fighters share equally in food and scarce cigarettes.

When the Army ventures from its camps to patrol, villagers warn the guerrillas of the military movements. As a result, the guerrillas are seldom forced to fight.

"The lack of a foreign arms supply is a problem," Elmer said. "But we're getting better and better at making our own weapons. We believe we will be able to stalemate the military even without foreign arms."