As he left Managua last August following the daring guerrilla raid he led on Nicaragua's National Palace, Eden Pastora, known as "Comander Zero" of the Sandinista National Liberation Front, vowed to a crowd of cheering supporters that he would return.

In recent interviews at his remote guerrilla headquarters, Pastora said he expects eventually to go back to the National Palace as Nicaragua's first elected president after the fall of Anastasio Somoza.

More experienced as a military strategist than a politician, Pastora does not suffer from lack of confidence in either field.

What is clear is that, following the palace raid and the appearance of his photograph - complete with grenade-laden bandolier and rifle held defiantly in the air - in newspapers throughout the world, Pastora has become perhaps the best known person in Nicaraguan next to Somoza.

Pastora is the undisputed military commander of the Sandinista troops, their chief tactician, and the closest the Sandinistas come to a figure approaching the standard of revolutionary charisma set by Cuba's Fidel Castro more than 20 years ago.

But he disputes all such Castro comparisons. "The only thing we have in common," he said, "is that we were both educated by the Jesuits."

The descendant of Sicilian immigrants to Nicaragua, Pastora has spent nearly half his 42 years fighting in the Nicaragua mountains against the Somoza family and the National Guard it controls.

Pastora said he decided to join the Nicaraguan guerrillas "in 1959, when I was studying medicine in Guadalajara, Mexico. We were having lunch one day - my brother, who was also a student, and my mother, who was visiting. There was a radio report of a student massacre in Nicaragua, in Leon.It made a great impact on me.

"There were lots of guerrilla movements in those days - as many movements as there were leaders."

Beginning in the early 1960s, a number of those movements began to merge into the Sandinista National Liberation Front. It is named after Augusto Cesar Sandino, leader of anti-Somoza forces who was assassinated in 1934.

While other Sandinista leaders tend to down-play training their members have received abroad, Pastora displayed no reticence in noting that "sure, there have been some trained in Cuba," particularly in the early 1970s. "It was the least Cuba could do," he said, "to train the enemies of its enemies," an apparent reference to the launching of the 1961 Bay of Pigs invasion of Cuba from Nicaraguan shores.

But "no matter what Somoza says," Pastora said, "I have had no outside training."

Pastora claimed that he would like to see "a Costa Rica type democracy" in Nicaragua. While he said he has no doubt that the more extreme leftist ideologues of the Sandinists "will never stop conspiring," he said he believed they would be neutralized "when there is freedom of speech in Nicaragua; when any communist, conservative, labor leader or liberal can attack anyone he wants to with words."

His most obvious current concern, however, is the Sandinista military situation.

During last month's civil war, including three unsuccessful Sandinista invasions of Nicaragua from Costa Rica, Pastora claimed, "our losses, among professional cadres, was very small. I would say about three percent out of hundreds" of the combatants.

The strongest of their three attacks over the Costa Rica border, on Sept. 17, when the Nicaraguan government accused Venezuela, Panama and Costa Rica of assisting the guerrillas, failed for several reasons, Pastora said.

"The arms came late, and we had to walk to the border for a long distance," he said. "There were only 60 of us that got across the border, only one of three columns. Initially, our plan was to take Rivas, [a small city north of the border outpost of Penas Blancas] but we were too late and [the National Guard] had already sent reinforcements."

Still, Pastora said, "we had an emormous military experience." In Penas Blancas, he said, "we were under constant fire for nine hours by tanks, mortars, artillery and airplanes. No Latin American movement has had the kind of experience that we have had."

Despite quantities of weapons taken from fallen National Guard troops and from raided arsenals, the guerrillas still appear no match for the government soldiers. Among the weapons seen at the camp were M1 rifles, some small caliber hunting weapons, and a number of M16 and what the guerrillas said were Argentine-made FAL automatic weapons, as well as several Uzi machine guns ostensibly from those sold to the Nicaraguan government by Israel.

Pastora accused Israel and the United States of heavily arming the National Guard.

"Somoza has enough guns to arm all of Central America," he said. The 5,000 M16 automatic weapons sold to Nicaragua by the United States within the past three years, Pastora said, "were not sold to fight against Honduras or Costa Rica, but to kill the Nicaraguan people."

Compared to recognized Sandinista political leaders, Pastora appears to have little ideology beyond the eventual installation of a democratic government, which he hopes to head, in a post-Somoza Nicaragua.