Guerrilla leader Jonas Savimbi now acknowledges his serious miscalculation last year when he predicted that the Angolan government's dry-season offensive would hit in the country's eastern panhandle.

The fighting was indeed fierce there during August and into September. Modern Soviet-made T62 tanks were ripping Savimbi's lightly armed battalions. But in the pitch of the battle, Savimbi got word that the government had opened up a second, larger front in the south.

In a matter of hours, it became apparent to Savimbi that he was the victim of a clever battlefield feint that had left his strongest assault forces 350 miles out of position.

It would take more than a week to move reinforcements south by truck. So Savimbi did the only thing he felt he could do: he called in the South African military.

At a bushland hideaway near this large logistical base on the Luengue River in early July, Savimbi discussed in detail and explained for the first time publicly South Africa's deep involvement in countering last year's government offensive.

Were it not for South Africa's intervention, many military experts have said, the offensive might have succeeded in overrunning Savimbi's forces and effectively crushing his National Union for the Total Independence of Angola (UNITA).

It became the battle for Mavinga, whose large airstrip would give the Angolan government what it needed to deal a final, crushing blow to Savimbi: a southern air base from which to fly Soviet-made fighters and bombers against UNITA's largest fortresses here and at Jamba.

"When we understood the major thrust was at Mavinga, it was too late," Savimbi said. "So we had to ask the South Africans to take 2,000 troops in four days and four nights from the eastern panhandle and put them here outside Mavinga .

"Then we said, 'Give us mortars, ammo and cannons of every quality,' and they gave it," he added.

To fly those reinforcements, the South African Air Force put at risk its American-made C130 Hercules transports, Savimbi said. The South African pilots flew more than 1,000 miles round trip through Angolan air-space to complete the airlift.

"It was a major effort," he said. "A Hercules can take a battalion with its support weapons and in a few hours put you where you want to be."

A private pilot, who regularly flies in the region and who asked not to be identified, said that last September, South African military authorities in Namibia banned all private flights near the Angolan border for two weeks at about the time Savimbi said the airlift occurred.

Savimbi denied allegations made from Luanda that South African infantry units and jet fighters carried out support missions for UNITA during the central government's offensive last year.

"The South Africans are -- how can I put it -- committed, you can say so," Savimbi said. "But the South Africans have their own problems and we think they will place their priorities on their own situation at home first, second in Namibia and third in Angola."

Therefore, he continued, "If they are not against the wall, I think they will do all they can to continue to support UNITA" because, he added, "I have no doubt in my mind that the South Africans see that if UNITA is crippled -- or let us take the extreme: wiped out -- it will have a very negative impact on southern Africa."South African Air Support in Doubt

South Africa has always claimed a stake in the Angolan civil war because it sees itself as the regional bulwark against spreading Soviet influence in southern Africa and would like also to undermine Angola's support for black nationalists seeking independence for Namibia and to overthrow Pretoria's white rule.

Should this year's offensive put Savimbi's back to the wall, however, the rebel leader said he does not believe that he could count on South Africa's airlift capability again, or any other form of air support.

"The South Africans will not sacrifice their air power to save UNITA for the simple fact that they now see that the Angolan government has improved tremendously their ability of detecting the planes and interfering with them."

Savimbi said his intelligence shows that Soviet and Cuban technicians have helped the Luanda government set up a radar network and sites for surface-to-air missiles in strategic locations across the southern and central portion of the country.

Due to this threat, Savimbi said, "I don't think the South Africans are in any mood to intervene massively with air power. They think that they may risk their own Mirages, which are not the most modern Mirages."

He said the Soviet MiG23s now in use by the Angolan Air Force were superior to the aging South African Mirages. But on the same day Savimbi offered this assessment, South African defense authorities unveiled their new "iron fist" strike fighter, the "Cheetah," which Pretoria advertised as a generational advance for the country's Air Force and a response to the threat from Soviet MiG23s in the region.Savimbi's Image Dominant

A reporter's 10-day visit to Savimbi's domain found Savimbi to be the monolithic figure at the top of the UNITA organization. He dresses in camouflage fatigues, wears a green beret and sports matching ivory on the handles of his cane and his Colt .45 sidearm.

According to a number of UNITA officials, virtually no military, diplomatic nor public-relations decision is made without Savimbi's personal approval. When a reporter on an excursion into the interior of the country asked his UNITA guide to change directions, the request took eight hours to go through scrambled radio channels back to Jamba and waited there until Savimbi could focus his attention on it.

A number of Savimbi's top lieutenants, such as Miguel Puna, secretary general; Tito Chingunji, secretary of UNITA's executive committee; Altino Sapalala, logistical commander; and Wambu Chindono, chief of intelligence, have demonstrated strong leadership capabilities. But to the outside world, and within the ranks of this guerrilla movement, Savimbi's image is dominant.

The cult of personality he has encouraged -- which has attended him during the 20 years he has been fighting whoever was on the other side in Angola -- raises the perennial concern among his outside supporters that without Savimbi there would be no UNITA.

At the moment, Savimbi is carefully managing his still burgeoning relationship with the United States. The morale and propaganda boost UNITA has taken from his successful trip to Washington last winter is everywhere in evidence in his camps. White House photos of Savimbi sitting with President Reagan in the Oval Office have been plastered on tree trunks with masking tape.

In case anyone misses these photos, Savimbi has had a 30-foot-high reproduction made on a hand-painted banner for use in political rallies. Other tree trunk photos show Savimbi with Secretary of State George P. Shultz and his predecessor, Alexander M. Haig Jr.

The nature of U.S. support for Savimbi still makes it awkward for him to discuss it. He will not say directly that he has received U.S. Stinger antiaircraft missiles from the Pentagon and Central Intelligence Agency, but he cannot suppress the obvious pride he feels to have received this prestigious level of support.

"The president has promised us support and we got that support . . . and it was delivered as quickly as was possible," Savimbi said. "We asked him to give us something effective against the air power and against the tank armor and . . . we got what we asked for," he added.

"And if there are Stingers or not Stingers, that's sensitive to me for the simple reason that I don't want the Angolan government and the Russians to know what I have."

Intelligence sources in Washington, however, indicated last month that the Reagan administration remains embarrassed that its decision to arm Savimbi with Stingers leaked to the press.

These sources said the administration has impressed upon Savimbi the need to keep this CIA assistance covert to avoid further diplomatic turbulence. Jordan's King Hussein complained publicly on a recent visit to the United States that his requests for Stingers repeatedly have been turned down, even though his regime has been a consistent and stable American ally in the Middle East.

The CIA training of Savimbi's forces on Stingers and U.S. light antitank weapons is said by sources to be taking place at a secure encampment where reporters are not allowed during visits to UNITA territory.

Savimbi said the new U.S. weapons are not yet "engaged in the battle," and indicated that they were being deployed to counter any attempted air strikes against the largest of UNITA's bases here and at Jamba.

This explains, according to one UNITA official, the construction of a number of 40-foot towers camouflaged to resemble the girassonde trees that populate southern Angola.

"When the offensive starts," Savimbi said, the U.S. assistance "will be effective."

Savimbi said he believes 1986 will be a critical year for him and the Angolan government, whose economy has been wracked by falling oil prices and guerrilla attacks.

In 1977, Savimbi predicted to a visiting correspondent that he, Savimbi, would be fighting until the end of the century, but he has now revised this estimate.

"We would need to make major mistakes to fight up to the end of the century. I think we are close within two years, he said and the other side, they are tired."

Savimbi said he thinks the Angolan government will make a major effort this year in an all-out offensive against his southern strongholds. "If the offensive fails," he said, "the allies of the Luanda government will start to have second thoughts. And if we fail in spite of the support from the Americans, the Americans will say, 'Look, these people are useless.' "

Savimbi concluded:

"I think this year will be the last offensive -- either they score big military points against us, or they don't score. If they don't score, they will negotiate."

Next: American policy vs. American oil.