Riding in Soviet-made tanks and trucks, an armored battalion of the Ethiopian Army rolled out of this dusty grove of mango trees three months ago. The soldiers rode up into the rocky, drought-dead hills of Eritrea to join yet another "final" offensive in Africa's oldest civil war.

They were part of the 200,000-man force mustered this fall by the Ethiopian government for its eighth major offensive here in the past eight years. They were after the Eritrean rebels who hold the mountains in this region in the northernmost part of Ethiopia, wedged between Sudan and the Red Sea.

This fall's offensive, which the U.S. government says was supported by $1 billion worth of Soviet weapons and ammunition, proved to be the most successful of the quarter-century-old war.

The drive seized more territory than any previous offensive and has left Ethiopia's Marxist government in its strongest position ever in Eritrea, according to U.S. diplomats, U.N. officials and western relief workers here in Eritrea.

Supported on the ground by Soviet T54 and T55 tanks, covered from the air by MiG23 fighter-bombers, Ethiopian troops overran scores of rebel-held villages. In a combined land, sea and air operation, they recaptured the towns of Barentu and Tessenei in western Eritrea. They took the rebels' key agricultural area in the Baraka Valley and established sea supply lines by capturing the Red Sea coastal plain.

Confident that the rebels were on the run, the government pushed back the curfew in Asmara, Eritrea's capital, from 11 p.m. to midnight.

Yet about 40 miles north of here, at Nakfa, the mountain fortress of the Eritrean People's Liberation Front, the government's offensive foundered last month.

"They were on a roll, their morale was really high, until they hit Nakfa," said a senior relief official with contacts throughout Eritrea.

The Eritrean People's Liberation Front has retreated deep into the hillsides near Nakfa and seeded approaching lowlands with land mines. When Ethiopian infantry and tanks tried to advance on Nakfa, they suffered heavy casualties, with 8,000 wounded and 1,200 dead, the senior relief official said.

Repeated air attacks with napalm and cluster bombs subsequently have failed to dislodge the rebels, diplomatic sources said. The once-prosperous town of Nakfa, meanwhile, has been reduced to rubble.

So far, the Ethiopian government has held on to all the territory it seized in the offensive, but it is too early to tell if the rebels will be able to counterattack and retake the territory they have lost as they have done in the past.

Stalemate and wholesale destruction of the countryside have been the hallmarks of the war between the Eritrean rebels, who are committed to creating their own nation, and the Ethiopian government, which is determined never to let that happen. Without Eritrea, Ethiopia would lose its two major ports and be landlocked.

The conflict, now grinding into its 26th year, has scarred and denuded much of Eritrea, exacerbating the damage wrought by nearly a decade of drought.

Perched in stone lookout towers on hundreds of hilltops in this region are young government soldiers, many of them teen-agers, clutching AK47s, squinting into the cloudless, whitish-blue sky, guarding the desolation.

Many of the government soldiers are conscripts from southern Ethiopia. They speak different languages and come from different cultures than the Eritreans. Relief workers said government soldiers treat civilians caught up in the war like foreign enemies.

Advancing soldiers routinely burn crops and houses, steal and shoot livestock and rape Eritrean women, relief workers said. Peasant farmers in Eritrea, as a matter of course, move their wives and daughters as far away as possible from Army encampments.

Government troops, themselves, do not have an easy time of it in Eritrea. Rebel leaders often comment on the willingness of government officers to waste the lives of their men. Not surprisingly, the rate of desertion in Eritrea is high.

Ethiopia's ruler, Mengistu Haile Mariam, who sometimes takes direct command of the fighting here, has administered harsh discipline on officers who perform poorly, as many have since the series of "final" offensives began in 1975.

Mengistu has ordered his officers shot when he considers their units delinquent, according to Paul B. Henze, a scholar specializing in Ethiopia at the Rand Corp. in Santa Monica, Calif.

When rebels of the Eritrean People's Liberation Front move out of the areas they have controlled for years, they, too, brutalize the citizenry, according to a senior official with the U.N. Children's Fund.

The government's fall offensive blasted through Mohammed Emir Ali's village one day two months ago. Ali, his wife and five children were asleep in their thatched-roof hut when government soldiers routed rebels who had held the village for years.

That morning Ali and his family became refugees in their own country. With five goats and the clothes on their backs, they were forced out to wander the land-mined and trench-slashed frontier of the war. Ali said he left behind the best crop of sorghum he had grown in years.

Ali and his family, along with about 140 other families from his village, straggled over a chain of mountains and arrived here in the first week in December. The children were among the most severely malnourished in the country. They are receiving U.S. food aid here through Catholic Relief Services' "northern initiative," which has followed the Ethiopian Army as it has fought its way north.

Ali, a wizened man of 60 who has been surrounded by soldiers and fighting for decades, echoed the sentiments of many Eritrean peasants when he said he had lost track of what the war is for.

"We cannot tell who is our enemy, who is our friend," he said. "All I know is we cannot go back to the place where we were born."

Besides the refugees created by this fall's offensive, who relief officials said number in the thousands, there are at least 190,000 Eritreans who have fled their homes for Sudan. According to a spokesman for the Office of the U.N. High Commissioner for Refugees, many of those refugees are fed up with the fighting and have no intention of returning to Eritrea.

The war grows out of Eritrea's longtime conception of itself as a country separate from Ethiopia, which is seen here as an imperialistic and hated interloper.

Much of Eritrea's identity as a nation was imposed by the Italians, who first colonized the region's two port cities of Assab and Masawa in the 1880s and stayed on until 1941. They built Asmara, an idyllic highland capital of wide boulevards and Roman-style villas swallowed up in bougainvillea and jacaranda trees.

They imposed their language, still widely spoken in the region, and welded Eritrea's diverse Christian, Moslem and animist peoples, its eight major nationalities, into a political entity.

After the Italians were expelled by the British in World War II and after a long U.N. debate, Eritrea was supposed to be guaranteed a measure of independence as an autonomous territory federated with Ethiopia.

The autonomy, however, never existed in Eritrea as it did on the paper of U.N. Resolution 390A of 1950. Ethiopia interfered systematically in the region's internal political affairs. It imposed a new official language, rigged elections and finally, in 1962, annexed Eritrea.

Guerrilla war broke out almost immediately. Eritrean rebels, who organized politically under a radical brand of Marxism, proved themselves fierce and resourceful fighters. For much of the past quarter century, they held de facto control over most of Eritrea outside the major towns.

They were supported openly by the Soviet Union until it became an ally of Ethiopia in the late 1970s. Western diplomats said that for some time the Eritreans have been supported primarily by Arab countries long suspicious of Ethiopia, including Saudi Arabia, Syria and Iraq.

According to Rand's Henze, the Soviets may still be helping the Eritreans, even as they have become the Ethiopian government's most important military patron. In a report on Ethiopia published earlier this year, Henze echoed the views of many relief officials in Eritrea and some government officials in Addis Ababa by writing that there is "widespread Ethiopian suspicion that the Soviets may actually be playing a double game with the EPLF."

The apparent purpose of the Soviet support for both sides, said relief officials, is to ensure Ethiopia's continued dependence on Soviet military support.

The rebels, however, have been crippled from the start by internecine squabbles. Until three years ago, when the Eritrean People's Liberation Front emerged as the dominant faction, the rebels spent a good deal of their energy and ammunition fighting each other. In the process, many observers said, they lost both their strategic advantage against the government and the sympathy of many Eritreans.

While Eritreans are growing increasingly weary of the war, Ethiopians outside of the fighting areas are told nothing about it by their government.

The Eritrean civil war, one of the world's longest playing conflicts, also is one of its least publicized. In Addis Ababa, 500 miles to the south of here, the government almost never mentions it.

Official silence reigns despite the government's successful offensive in Eritrea this year and despite the fact that hospitals in the capital have been full of badly wounded soldiers for months.

The international famine relief effort in Eritrea has lifted the curtain on the government side of the conflict in recent months. Before the U.S.-funded "northern initiative" feeding program began in September, allowing relief workers and a few journalists to travel near the fighting areas, nearly all the information about the Eritrean civil war came from the rebel side.

For peasants who are not rebel supporters, one major positive result of the government offensive this fall is that it has opened up previously cut off regions of Eritrea for an increasingly effective famine relief operation.

"One advantage of the war is that the Ethiopian Army has improved the roads for their armored vehicles to the point where they can handle large food relief trucks," said Rev. Keflemariam Fadega of the Ethiopian Catholic Secretariat in Eritrea.

The United States has pledged 25,000 tons of food for Eritrea and the nearby Tigray region, which has its own rebel war. About 3,000 tons of food from the program were distributed last month in Eritrea.

Both Catholic Relief Services and the International Red Cross, which operate in the region, predicted that the escalating war and continuing drought will strike Eritrean farmers with a vengeance next year, when food from this year's meager harvest runs out.

"I fear that in three or four months, we will have to sharply raise the distribution level to avoid a catastrophe," said Paul J. Loosli, a Red Cross representative in Eritrea.