At the village of Sorkhab Dara, an hour's walk downstream from this major guerrilla base, it was clear why the Afghan resistance fighters doing battle with Soviet and Afghan government forces in the region are now being forced to do without support from local residents.

There are no local residents.

Between 20 and 30 houses, many with shell holes in their crumbling walls, stood abandoned and silent. Fields that normally grow wheat lay barren, glinting with heavy, jagged chunks of steel -- fragments of bombs that had carved deep craters and uprooted trees.

Here in Logar Province, where the guerrillas and the Soviet-led forces battle for control of supply routes critical to both sides, the Soviets have forced out much of the civilian population with scorched-earth tactics and retaliatory strikes against villages near the sites of guerrilla attacks. Where villagers remain, they have become more circumspect in their support for the anticommunist rebels.

At a mosque in another village, a group of exhausted Afghan resistance fighters, or mujaheddin, leaned their Kalashnikov assault rifles and antitank rockets against the whitewashed walls, said their evening prayers and collapsed on the straw-covered floor.

After a long day's reconnaissance through the surrounding countryside, the guerrillas had stopped for the night in the nearest mosque, as travelers in rural Afghanistan traditionally do. Within a few minutes, elders of the village -- about 10 miles south of the capital, Kabul -- arrived with young boys, who carried food and water for the visitors.

Seating themselves in the pool of yellow light from a kerosene lantern, the older men welcomed the mujaheddin and then asked warily about their plans. The villagers discouraged any idea of a guerrilla attack on a Soviet and Afghan government post about a mile and a half away.

"Our young men are gone," explained a bearded and wrinkled-faced elder. "Only old men, women and children remain here," he said. "If you are going to attack the Russians, we must prepare to leave our homes, because afterwards, the Russians will come to kill us and there will be no one to stop them."

The mujaheddin reassured the older men that they were not planning to launch an attack from the village and would be leaving after a few hours' sleep, as soon as the moon rose to light the long trail back to their guerrilla base.

During a 10-day trek into northern Logar, incidents such as the conversation in the village mosque highlighted a dilemma facing Afghans who have fought for 6 1/2 years since the Soviet invasion: with better supplies of light weapons, the guerrillas are able to attack more effectively the positions of the Soviets and Afghan government, but, lacking effective air defense, they cannot protect their villages and civilian supporters against Soviet retaliation. Mujaheddin in different parts of Afghanistan have responded in different ways to this dilemma.

Facing guerrilla war with a reduced base of civilian support, mujaheddin in this part of Logar have moved their bases away from the villages and into more remote and protected areas. They say they now put greater emphasis on mobility and look to nearby Pakistan as a source for supplies once found locally.

The guerrillas with whom I traveled into Logar are members of Mahaz-i-Milli Islami, the National Islamic Front of Afghanistan, one of the major Afghan resistance parties. This year, these mujaheddin moved their base from an abandoned village into this steep-walled canyon here, eight miles southeast of the Soviet-held town of Mohammad Aghah.

From the canyon base, Mahaz-i-Milli sends small "mobile groups" of 10 to 12 fighters out onto the desert plateau where the road from Kabul crosses to the south. On the plateau, they may circulate, moving among hiding places, and watching for Soviet or government convoys -- or they may link up with other groups for joint attacks on Soviet posts.

From this new, more remote base, it may take the mujaheddin four more hours of walking to reach their targets on the Kabul-Gardez road, or near Mohammad Aghah. When winter makes movement difficult, the mujaheddin will disperse to their own families in refugee camps in Pakistan or in villages in the district, from which they will conduct only limited operations.

The style of warfare here differs from that in other strategically less critical, areas of Afghanistan where there is little Soviet or Afghan government presence. In a visit to southern Wardak Province last fall, for example, I saw large districts where the mujaheddin do less fighting, focusing instead on keeping a civilian population base to support military activity in adjacent areas.

In all, five of seven villages visited during the trip were abandoned, although most were not destroyed as completely as Sorkhab Dara. Around a bend in the canyon, a small group of mujaheddin stopped under trees of ripening apricots and mulberries and ate their fill. "Now that the people are gone, we are the only ones to harvest the fruit," said Ahmed Ji, a local commander.

Where the local villagers were once able to supply the mujaheddin with meat, vegetables and even fresh bread, the fruit from the village's abandoned orchard is one of the few kinds of food the mujaheddin can still find locally. Staples, supplied by the party, are packed in from Pakistan.

On our way to Logar, we had stopped at a depot in the Pakistani town of Parachinar, where Mahaz-i-Milli stores rice and lentils in burlap sacks, piled to the ceiling.

"A couple of years ago, we did not have to send in food with our mujaheddin," explained Rahim Wardak, a senior Mahaz-i-Milli commander, "but now the Russians have forced so many people to abandon their villages, we have started a regular system to send food for fighting" in the depopulated areas.

Only a two to three days' hike from the Pakistani border, mujaheddin from northern Logar are able to replace their local supplies with imports. Many guerrilla groups from northern provinces need as much as a month to reach their home areas, and must continue to rely on local food supplies.

"We come to Pakistan each spring for weapons," said a Jamiat-i-Islami (Islamic Society) commander from Baghlan Province, whose group had stopped along the caravan trail from Pakistan. "We cannot carry food."

Supply routes are at the center of the war in Logar. The mujaheddin here fight to keep open this stretch of a critical guerrilla supply line from their bases in Pakistan to Afghanistan's northern and central provinces. They also attack Soviet and government convoys on the nearby road from Kabul to a major Soviet garrison at Gardez, south of here.

Haji Mohammed Gul, a commander of the Ittihad-i-Islami (Islamic Unity) party stressed that the mujaheddin now rely more heavily on supply routes, not only for food, but for weapons. "In the beginning, we fought the Russians with captured weapons only," he said. "But as our fighting has become more sophisticated and intense, we are more dependent on the trails to Pakistan."

Habib, a tall Pathan guerrilla who remembers much of the English he learned years ago from a Peace Corps teacher, explained why both the supply trail and the local bases of six of Afghanistan's seven main resistance groups are hidden in this canyon.

Squinting up at the bright narrow slice of blue sky between the canyon's sheer cliffs, rising hundreds of feet overhead, he smiled and said, "It is our special Afghan air defense." Along the canyon bed below, trains of camels and horses plodded toward central and northern Afghanistan, with antitank rockets, land mines, mortars and rifle ammunition lashed to their backs.

In mid-May, the Soviets and Afghan government poured thousands of troops into an offensive near the Pakistani border, designed to close off this trail near its source -- the Pakistani town of Teri Mangal.

But throughout the trip to Logar, in late June and early July, the trail was busy with guerrillas urging caravans through the valleys and over mountain passes, toward Afghanistan's interior. Indeed, in the final 24 hours on the trail as we returned to Pakistan, we counted 217 camels and 130 horses heading into Afghanistan -- a train of animals the mujaheddin estimated would carry 35 to 40 tons of supplies.

But if the trail is open, the passage is not easy.

"Last August, the Russians reinforced their bases at Jaji," where the supply trail crosses from Pakistan into Afghanistan, explained Ahmed Ji, the Mahaz-i-Milli commander, "and since then we have been able to cross that plain only at night."

As everywhere in Afghanistan, the mujaheddin were worried about air attack while on the trail. But in a marked difference from the trip last fall into areas further south, the mujaheddin of Logar were much more worried about pro-Soviet spies along the route.

Often, when we arrived at a crowded teahouse along the trail, our group would stop some distance off, sending a member in to buy tea -- thus preventing others inside from noticing the presence of a foreign traveler. "We don't know who they all are, and if there is a spy, he could easily call for the helicopters to attack us," explained Ihsan, my translator.

In late June, about 10 tons of ammunition and supplies were destroyed when Soviet Sukhoi jets bombed a caravan of about 100 animals that had stopped in an Afghan village near the start of the supply trail.

Dominique Vergos, a French journalist who traveled with the caravan, suggested it had been pinpointed by a local spy who had called in the air strike. "Fifteen minutes after we got to the village, suddenly the planes were there," Vergos recalled.

"The mujaheddin were very careless though," he said. "They are often like that, stopping in an open place instead of scattering the animals in hidden places -- and with all that ammunition, they were even smoking."