Three years ago Pedro Pablo Ortiz Centeno, known now as "Commander Suicide," was hiding out with fewer than a dozen other members of the Somoza dictatorship's defeated National Guard in the unforgiving hills of northern Nicaragua. They ate monkeys and were armed with nothing but shotguns, pistols and old .22-caliber hunting rifles.

Now Suicide commands the men and firepower to fight battalion-size engagements with the regular forces of the Sandinista Army.

The odyssey of this former first sergeant and sometime assassin reflects the complex development of the U.S.-backed anti-Sandinista movement from a ragged collection of exiles to a dangerous and powerful guerrilla army. But his past actions and associations in the National Guard also represent part of the most serious political problem that his counterrevolutionary group faces--whether it can persuade international opinion that it lives up to its name as the "Nicaraguan Democratic Force."

The Nicaraguan National Guard was less an army than the personal police force of the Somoza family, the agency of its massive corruption, the protector of its 42-year dynasty.

As the vast majority of Nicaraguans and world opinion turned decisively against President Anastasio Somoza in 1979, the National Guard waged a brutal, if brief, fight to save him and themselves. Bombing civilian populations, summarily executing young men and women in the streets, they only worsened the hatred felt for them and the man they defended.

The guardsmen, politicians and family allies of Somoza who fled into exile after their defeat were at first unable to create a credible opposition to the Sandinistas. But as the leftist regime in Managua appeared to embrace Cuban and Soviet views, it alienated many originally disposed to tolerate, if not actively to support it.

With extensive prodding from Honduras and Washington since its founding in 1981, the Nicaraguan Democratic Force has pulled together members of the old Nicaraguan Conservative Party--the main opposition officially permitted under Somoza--a weeded-out group of national guardsmen needed for their military expertise and a growing number of private businessmen who initially tried to work within the Sandinista system but have since given up and gone into exile.

It is a group without any coherent ideology beyond its anticommunism and an expressed but vague commitment to create something like a conventional western democracy in a country where such a thing has often been a professed goal but never reality.

The presence of soldiers like Suicide in the field and of former National Guard Col. Enrique Bermudez in the leadership of the Nicaraguan Democratic Force has led to the refusal of Eden Pastora, the Sandinista revolution's most popular hero and as a defector potentially its most dangerous opponent, to have anything to do with the force.

Some force members suggest that Pastora, who has shown no military strength since he publicly declared his opposition to the Sandinista leadership a year ago, may have lost the will to fight. But they also feel they need him.

A member of the force directorate said that Pastora has "everything we don't have--like credibility. He has a license to kill. He blows a bridge, and he'll be a hero. We do it, it's a massacre."

There are also fears that Pastora could somehow take everything away from them. "We are worried," said the force leader, "that we are doing the fighting so Pastora can take the political victory."

Pastora's acquaintances remember his own feeling that he did the tough fighting on the southern front during the insurrection only to have other members of the Sandinista front march into Managua first and get the credit he felt he deserved. Some suspect he would take that role himself this time.

As it happened, one of the national guardsmen fighting Pastora's units near the Costa Rican border in 1979 was 1st Sgt. Pedro Pablo Ortiz Centeno, a member of the crack batallion called the Cascabeles, or rattlesnakes.

Seven hundred of them were holding Pastora's forces down around Penas Blancas when the government they represented disintegrated on July 19, 1979. Demoralized, they commandeered any boats they could to make their escape to El Salvador.

Even before the end of 1979, however, Ortiz Centeno said he had made his way to Honduras and back into Nicaragua. He had won the cooperation and support of several Honduran junior officers at a key border post, who agreed that the Sandinistas were communist and the threat must be fought at any cost. They gave him a couple of old rifles and a pistol.

Those were the most hopeful and popular days for Nicaragua's Sandinistas and the most desperate for Ortiz Centeno and the small band of men who had stayed with him since Penas Blancas. The new regime in Managua was carrying out a national literacy campaign, trying to teach virtually a whole country to read in a matter of months.

Ortiz Centeno, convinced it was all a deception, roamed with his men, assassinating Sandinista political targets one by one as they could.

Julio Cesar Herrera, 28, now known as Krill, says the group assassinated a Cuban teacher in the town of San Francisco del Norte. Krill also talks matter of factly of murdering a militia commander near the border at Guasaule after the commander made the mistake of throwing Krill's mother in jail for 17 days. There were other victims, he said without giving details.

The Hondurans, meanwhile, were not always helpful. Although Ortiz Centeno briefly ran a training camp for 240 men near the Honduran settlement of La Cruzita, they marched only with sticks since there were no arms available to them and many of the early "contras," as the counterrevolutionaries are called, were constantly in and out of jail.

As late as 1981, Ortiz Centeno said, it was still a major event for his group when a local militia commander secretly conspiring with them gave them 10 old M1 rifles.

But the counterrevolution, despite growing disillusionment with many Sandinista policies, did not begin to take serious shape until early 1982, at about the time the Reagan administration approved $19 million in covert backing for the rebels and a new government was elected in Hon- Men like Ortiz Centeno were considered perfect for the new army, although he was once accused of murder in 1970, the year after he joined the National Guard and spent six months in the stockade for injuring another soldier. As a peasant and an enlisted man he had been excluded from the worst corruption of his institution. duras with a new ambitious army chief of staff, Gen. Gustavo Alvarez, who encouraged rebel activity.

A group known as the September 15 Legion, cofounded by Bermudez and others, began to operate with some success and at least tacit support of Honduras through 1981, but even many of its former members now admit it was riddled with some of the worst elements of the old National Guard.

There were recurrent incidents of drunkenness, even bank robberies in Honduras. The legion was finally dissolved into the broader-based Nicaraguan Democratic Force and a purge was begun.

"We allowed them to be trained and everything," said a Honduran officer interviewed in Tegucigalpa. "But we also cleaned a lot of the corruption." The idea was that a lot of nonguardsmen would have to be included in the force before it could be successful politically or militarily.

While the Nicaraguan government has charged that followers of Somoza help finance the Nicaraguan Democratic Force, the current leadership has been carefully selected to exclude those with close personal ties to the former dictator, who was assassinated in 1980.

"They were cleaning house for a year, getting rid of some bad apples," said the officer, adding that the Hondurans and U.S. officials can still tighten the leash on the rebels if they want. "They will never have enough logistical support if they start behaving stupidly. How we treat them depends on how they behave."

Men like Ortiz Centeno were considered perfect for the new army, although he was once accused of murder in 1970, the year after he joined the National Guard and spent six months in the stockade for injuring another soldier. As a peasant and an enlisted man, however, he had been excluded from the worst corruption of his institution and he proved to have a natural ability to inspire confidence among his men.

He received special training for a month, he recalls, from a Cuban exile he knew as Bon 2, a veteran of the Bay of Pigs, he said, who has a withered arm.

There were multiple levels of command and parallel levels of fronts and deceptions in this covert creation of the force into which he was integrated under the name of "Suicide".

Argentina was participating in a major way with training and advice, but that country was also the source of frequent frictions, according to informed military sources. Animosities between the U.S. advisers and the Argentines were raised by the 1982 war over the Falklands Islands thousands of miles to the south. Despite the Honduran chief of staff's longstanding affinity with the military men from Buenos Aires, other Honduran officers complained bitterly that the Argentine advisers overstepped their authority at special counterrevolutionary training schools, such as one at Laterique in the mountains outside the Honduran capital.

"Our people said 'Wait a minute, these guys the Argentines are a bunch of fascists,' " recalls one Honduran official, adding that they were told "You talk politics at the top, not here. You work here."

The Argentines reportedly have turned over much of their training activities to the Hondurans and Nicaraguan exiles themselves during the past few weeks.

About three months ago, according to sources in the Nicaraguan Democratic Force, most of the training was completed. Except for a command and control center, the border camps, which had been magnets for international attention, had largely disappeared as the new army took up positions deep into the Nicaraguan interior.

As the fighting intensifies, new leaders are emerging, and Ortiz Centeno has fit easily into the new mold. He calls the hard-faced veterans around him by their noms de guerre--Delta, Bad Face, Joshua, Echo, Bird, Krill, Rasputin--and acts like a father among children, playing cards. At one point he handed out marshmallows to men who had been risking and inflicting death with him all day.

Suicide's troops make up a tightly knit and disciplined family. His common-law wife, known as La Negra, handles much of the logistical support and is respected as a commander herself. She laughs and jokes constantly and easily with the soldiers who might be called her boys. She even gave many of them the exotic pseudonyms they use.

The former guardsmen speak of their decision to fight as their only alternative to a live of exile or jail in Nicaragua.

In the field, every march, every combat, every rest is also something of a training exercise. Guns are repeatedly cleaned and oiled. The line of march is watched to make sure the troops don't bunch up and become vulnerable to ambush.

Suicide's following has grown steadily with his image of canny strength and coolness. Looking back on what he refers to as "the days of the .22s," he remembers peasants telling him they wanted to fight but never had a chance. "Now," he said, "we walk here as the lords of this land."