Two weeks after the government launched an ambitious offensive against leftist guerrillas in their bastion of Morazan province, the operation has begun to wind down with few concrete results.

Despite official insistence that the operation into the long-time guerrilla stronghold in northern Morazan has been successful, the Army appears to have failed to accomplish its main objectives as well as to have suffered an unannounced number of casualties and the loss of four of its top field commanders.

When the operation was launched by 2,300 Salvadoran troops three days after President Jose Napoleon Duarte's ground-breaking peace talks with guerrilla leaders in the town of La Palma, the operation's field commander, Lt. Col. Domingo Monterrosa, told reporters the objective was to try to capture Joaquin Villalobos, the leading guerrilla commander in the region, and to knock out the transmitter of the guerrillas' clandestine Radio Venceremos.

Although a radio relay station was captured near the town of Joateca, Radio Venceremos has continued to broadcast daily reports of the fighting, even boasting that it has dealt the Army a punishing blow by killing or wounding up to 87 government soldiers. The Army has denied that figure, but it has declined to announce its total casualties.

Not only did the helicopter-launched attack on northern Morazan fail to capture Villalobos, or any of the other major guerrilla commanders who were thought to be in the area to discuss with him the La Palma talks, but Monterrosa, acclaimed as the Salvadoran Army's top field commander, died when his helicopter crashed, killing all 14 persons on board, including three other senior field commanders.

Radio Venceremos immediately said the helicopter was shot down outside Joateca by guerrilla machine gunners who had infiltrated into the hills around the town specifically to shoot at Monterrosa's helicopter. The government has insisted his helicopter crashed because of an unspecified "mechanical failure."

In his air-conditioned office here at the barracks headquarters of the region's 3rd Brigade, Lt. Col. Miguel Mendez, who was named Monterrosa's successor within hours of the commander's death, insisted Friday that the operation was still "positive" even though no major contact had been made with the guerrillas.

"What we have done is to keep them on the run, to prevent them from grouping and to keep them off guard," Mendez said, admitting that the loss of Monterrosa was a blow to the Army.

Mendez, who had been the Army's chief of operations before being appointed to succeed Monterrosa as commander in the country's three eastern provinces, maintained that despite the lack of contact with the rebels, he was convinced that they were weaker than they had been two years ago when he last was on an operation in Morazan.

"Then," he said, "we had strong contact with the guerrillas for five or six days in a row. The fighting was often heavy."

This time, he said, there had been only a few hit-and-run attacks, small ambushes and mines laid out behind the guerrillas, who had retreated into the hills as the Army advanced.

Mendez gave no number for guerrilla casualties, stating that in the difficult terrain in which they were operating it was hard to determine how many of the enemy had been killed or wounded. Two days before he was killed, Monterrosa had told reporters that only three guerrillas had been killed and 11 captured. Mendez declined to discuss government losses beyond saying that they, too, had been small.

He admitted, however, that he did not believe there was a great number of enemy casualties, though he said his troops had overrun several abandoned guerrilla camps and training schools, captured a large amount of rebel documents and propaganda, and seized a number of weapons and ammunition stocks.

Another major objective of the operation that has not been accomplished was Monterrosa's stated desire to move refugees from northern Morazan back to their homes behind his troops' sweep.

He had particularly sought to repopulate the town of Meanguera, just north of the bridge over the Torola River that divides the southern and northern parts of Morazan province. The bridge was blown up by the guerrillas in early 1982, separating the two areas.

Girders and other parts for building a temporary Bailey bridge across the river have been brought up to the destroyed bridge, and plans have been announced for refugees from the north, now grouped in squalid, overcrowded camps south of the river, to help build the bridge so that they can return to the north.

A group of refugees from the northern town of Perquin, which has virtually been the guerrillas' capital in northern Morazan for most of the past four years, were gathered at the bridge and ready to work this week.

But they said that they and their families would not move back into their homes in the north until they were assured that the war would not again catch them.

Most of the refugees at the Torola bridge said they had small coffee holdings near Perquin and would go up there to harvest their crops when the bridge was built, but probably would not stay.

Mendez admitted that despite Monterrosa's hope that government troops could be stationed permanently north of the Torola after the operation, this probably would not be possible because the guerrillas still had the ability to mass sizable forces to attack any stationary garrisons the Army might establish.

"If we put 50 soldiers in one place, they can still mass 200 to overrun them if they want," Mendez said. "If we put 200 there, they can still bring 800 against them."

Mendez said that, although several units involved in the original operation had been withdrawn, the operation would continue at a lower level, with the Army's elite Atlacatl Battalion continuing mobile operations around northern Morazan for the immediate future.

As he spoke to journalists, there were signs of the winding down of the operation on the parade ground just outside his office.

A UH1 medical evacuation helicopter was being loaded with two coffins carrying soldiers killed in Morazan that morning, while about 500 soldiers fresh from the fighting had gathered in civilian clothes to be given eight days' leave.

As they filed out of the gate, none seemed to pay any attention to the coffins being loaded for transportation to the capital of San Salvador.