The troop convoy north to Mavinga is two nights and a day on a mechanical bull.

The brutal Star trucks of Russian design and Polish assembly pound and smash through dense forests, fields of savanna grass and marshlands. There are rivers to ford. The sandy road is little more than a jungle track. Deep potholes, fallen trees and gullies are its signature. When the obstacles are too great we crash into the forest, knocking over small trees to cut a new trail.

On a straight line, the distance from our old camp to Mavinga is less than 100 miles, a two-hour drive in America. On this convoluted track, the trip takes 30 hours.

This road is Jonas Savimbi's logistical lifeline for his rebel forces, his Ho Chi Minh trail. It begins nearly 200 miles south at the Namibian border where supplies of diesel fuel come in from South Africa. It ends about 50 miles northeast of Mavinga, the scene of the National Union for the Total Independence of Angola's [UNITA] most substantial military victory and the northern-most outpost for Savimbi's battalions.

Mavinga itself could be the stage set for a colonial melodrama. It sits on a barren, dusty plain, surrounded by nothingness. I could imagine becoming very violent and depraved after a few years under this broiling sun. Joseph Conrad could do it justice. The town's two streets are lined with orange trees, stucco buildings and houses with tile roofs. Most of them are gutted from the recent fighting. The orange trees are the only saving feature.

It is the second largest town in Cuando-Cubango Province and has been an administrative and trading center with a police barracks under both the Portugese and the present government of the Popular Liberation Movement of Angola [MPLA] which vanquished UNITA in a civil war during the mid-70s. To UNITA it is a precious jewel, a tangible symbol of its capacity to attack and defeat in open country a modern army of Angolan troops backed up and supported by Cuban troops and Soviet logistical help.

Jonas Savimbi insisted that I come here to prove to myself -- and the world -- that Mavinga had fallen, an even that has never been announced by the MPLA government. That government has also repeatedly declined to allow Washington Post reporters to visit the country and to evaluate the MPLA accounts of the struggle with Savimbi, whom the MPLA claims is no more than a bandit capable only of sabotage actions. What follows is UNITA's version of the battles for Mavinga:

An MPLA brigade of 2,000 men guarded the town and its 3,000-yard airstrip last Sept. 19. Two other large contingents were in place 50 miles to the west -- 6,000 Cubans and government troops at Menongue and 4,000 at Cuito-Canavale. UNITA attacked in daylight with four battalions, about 2,500 men. They swept over the airfield, hit the brigade command post and after four hours had routed the MPLA and inflicted heavy casualties.

Graves now line one end of the airstrip. The ground is littered with spent munitions and abandoned gear.

In March and again about a month ago, major effects were made by the MPLA to retake the town. Both failed. The relief forces were ambushed by UNITA battalions 40 miles west of Mavinga; 800 MPLA troops were killed by UNITA's count. Its own casualties were light. Hundreds of weapons, large stores of ammunition and more than 70 trucks were captured in the Mavinga actions including the despicable iron monsters that brought us here.

The significance that UNITA attaches to this series of engagements is hard to overstate. It proved to the troops and their commanders that they could function as a conventional army, not merely as hit-and-run guerrillas fighting from ambush. It proved that they had the command structure, the logistics, the communication and tactical skills to defeat forces with superior equipment and air support. A huge Antonov cargo plane, capable of carrying T62 tanks, was shot down in the fighting, along with a helicopter gunship.

The battles also proved that UNITA could not only take but hold an exposed position in an area with heavy MPLA troop concentrations. The value of the captured arms and equipment is inestimable to an army with no other visible source of supply.

Col. Renato Mateus, UNITA's intelligence and operations chief, gave me his perspective on the fight. Since 1979, he said, UNITA has had 13 "significant" engagements with MPLA forces, resulting in 1,609 MPLA fatalities. More than 1,000 of those killed died in the Mavinga engagements.

His description of the battles closely matched the accounts later given to us by MPLA prisoners. The captured arms and equipment are on public display. The carcass of the Antonov still lies in the bush. A Soviet pilot and mechanic are in UNITA's hands.

So there is no reasonable doubt that something important happened at Mavinga so far as Savimbi is concerned. There is also no doubt that something important happened so far as the MPLA says, nearby Cuban battalions refused to come to the MPLA's rescue and refused to send helicopters to remove the wounded. In fact, UNITA battle summaries of the past three years fail to note a single engagement with Cuban forces. This is consistent with other reports and with statements made to me by two Cuban deserters held by UNITA.

The Cuban forces -- whether 20,000 as the United States has claimed or 36,000 as Savimbi and the deserters claim -- have largely retired from the fighting; they are garrison troops in the larger towns and cities or are assigned to the defense of such strategic assets as birdges, factories, the Gulf Oil facilities and the diamond mines owned and operated by South Africans. The Soviets, too, seem to be playing only a supporting role, ferrying troops and cargo, for example, and even that role appears to have been curtailed since the loss of several planes to UNITA missiles.

We leave Mavinga after another choral concert by the 32st Battalion and after acquiring our loot -- bushels of oranges picked from the Main Street trees. The ride south to the operational headquarters of Brigadier Demosthenes Chilingutila, UNITA's chief of staff, is another 10-hour horror. Ralph Nader is needed here to check out these Star trucks. They are in conspiracy with the organ transplant industry.

It is very late at night when we arrive at Chilingulita's camp. A surprise is waiting. A surging mass of men lines the trail, singing, dancing and emitting war cries. They are troops of the 275th and 210th Battalions, veterans of the Mavinga action.

They lead us to a huge fire encircled by hundreds of soldiers. The singing resumes -- patriotic songs, hymns to Savimbi, celebrations of battles past and to come.

Into the fiery circle leap five dancers in masks and feathered costumes. They represent five of the major tribes of Angola. Their dance is an ancient ritual of welcome to strangers. Each dancer competes with the others to win the hearts of the visitors.

Miguel Puna, our escort on this long trip, is ecstatic. He is an African chauvinist, a peasant down to his bones, a man contemptous of Westernized African intellectuals and, I suspect, flabby white journalists. He could have danced all night.

I beg off again to Puna's displeasure. We have gone three nights without sleep. The troops are still singing and the dance goes on as I crawl into my bunker.