"Watch!" whispered Mohammed Amin, pointing back at a Soviet Army post that we had crept by only moments before.

Amin's unit of Afghan guerrillas had just led me, slipping and stumbling, on a serpentine path through muddy streets, irrigation ditches and empty fields on the outskirts of this provincial capital. A cold wind was blowing away the clouds and rain that had blackened the night while we filtered cautiously through a double ring of guard positions defending the town.

We had passed less than 100 yards from one post and had clearly heard Soviet soldiers shouting orders to halt. Now, as the growing moonlight gave shape to the darkened neighborhoods of Ghazni that spread downhill from us, we heard the first few rifle shots as other guerrillas attacked the post Amin had indicated.

Then the night exploded.

The deep staccato of Soviet heavy machine guns and the concussive whump of mortar rounds drowned out the guerrillas' Kalashnikov rifles. Streams of glowing tracer bullets etched across the silhouettes of abandoned homes, and flares burst into harsh white light overhead.

"If we shoot one bullet at them," Amin said later, "they shoot 10 back at us, plus mortars -- and if the helicopters can fly, they shoot rockets, too. If we attack one post, they shoot from four or five posts . . . but they aim very badly."

The spectacle of Soviet firepower had punctuated a reconnaissance mission by Amin and about a dozen local mujaheddin (holy warriors, or resistance fighters) from the Mahaz-i-Milli, the National Islamic Front of Afghanistan, one of the smaller of Afghanistan's main resistance groups. They were choosing sites from which two nights later they would attack Ghazni's airport and the Soviet and Afghan Army garrison in the town's center.

I had asked to accompany the mujaheddin into Ghazni to try to understand something of what seemed an oddity: that outgunned and ill-trained men -- mostly illiterate farmers and shepherds -- have battled the powerful Soviet Army to a six-year standoff in Afghanistan.

Since their invasion, the Soviets have held Afghanistan's cities and provincial centers, with the support of the smaller and unreliable Democratic Republic of Afghanistan Army. The mujaheddin control the countryside and mountains, and each side remains unable to dislodge the other.

Ghazni, 78 miles southwest of Kabul, the capital, is an important center along the Soviets' main supply route to Afghanistan's south and west. The mujaheddin, who frequently exaggerate the size of enemy forces, said about 12,000 Soviets and not more than 4,000 Afghan Army troops are based there, with support from artillery and the garrison's helicopter base.

The mujaheddin, many of them former residents of Ghazni, live at guerrilla bases in nearby mountains and receive food and information from villages. During the last year, the Soviets have tightened defenses around Ghazni, as they have around all the towns and cities they hold.

Before, "we conducted our operations from within the town, and went in both day and night," said Jalat Khan, 35, a former shopkeeper who now commands a guerrilla unit of the Harakat Islamic Revolutionary Movement, another of the seven main Afghan parties. "But this year, they tripled the number of guard posts around the city, so now we fight only at night."

Jalat Khan said that according to duty rosters smuggled out to him by sympathetic Afghan officers, two-thirds of the soldiers in each post are Soviet and one-third Afghan. "Even if the [Afghan soldiers] do not fight well, the Soviets need them because they know the local people," he said.

Agha Mohammed, 40, a former colonel in the Afghan Army, passed information to the mujaheddin until his activities were suspected and he was imprisoned in 1980. Released after a year in Pol-i-Charki Prison, near Kabul, he immediately joined Mahaz-i-Milli resistance force. "Many officers who are still helping us want to come out to fight," he said. "Working from inside is very dangerous, but we ask them to stay as long as they can."

As with most resistance attacks on a Soviet stronghold, the assault I witnessed could not have altered the Soviets' fundamental control of the town. Only in a few cases during the war have mujaheddin threatened to capture a major town outright, an event that has led the Soviets to use large offensives to regain control.

The mujaheddin attack to inflict casualties and capture weapons. Weeks after the attack that I watched, the mujaheddin, after receiving reports from their informers inside Ghazni, claimed to have killed 36 Soviet and Afghan Army soldiers and injured 29 and to have damaged government offices, the airport and the town's main military garrison. The Attack

Late one afternoon, we descended the ravine from the Mahaz-i-Milli guerrilla base to an abandoned village at the edge of Ghazni's plain. About 45 mujaheddin gathered to hear their commanders explain their plan: three different groups would attack at once, firing missiles, mortars and recoilless rifles at targets in the town's center and at the airport.

I was told to accompany Sanaye, a short, thin commander in his 30s, whose dozen mujaheddin included an English speaker.

As always during my month inside Afghanistan, I wore the same traditional Afghan clothes as did the mujaheddin: a long shirt hanging loose outside baggy trousers, a wool cap and a blanket. It had seemed an intelligent concession to wear my good American running shoes.

We crammed ourselves into a pair of Russian-made trucks, which had been driven out from the city, and spotters climbed on top to watch for the Soviets' much-feared helicopters. As we rode across the rolling plain toward Ghazni, the mujaheddin -- most in their teens and early twenties, sang and clapped, like a high school band on its way to a football game.

On a dirt road near Ghazni, the setting sun cast a yellow light on the guerrillas as they climbed out of the trucks and prostrated themselves on their blankets in prayer. As the daylight faded, we crept toward the first guard post.

It was here, two nights earlier, that I had asked my translator, Mohammed Amin, what it was that the Soviet soldiers had been shouting. "They are calling, 'Halt or we will shoot you!' " Amin had replied.

Sensing my shock, he had added quickly, "Don't worry . . . . They cannot see us. They always shout this at night whenever they hear some noise."

I was not always calmed by such reassurances from my host. Although the mujaheddin fear and respect the powerful and sophisticated Soviet weapons, they have a low opinion of Soviet soldiers. That and their confidence in their own superior knowledge of the terrain often gave them a relaxed air that I, in my own nervous state, sometimes found alarming.

The mujaheddin were fascinated by my habit of whispering notes into a small tape recorder as we walked through the town. Often during moments of heavy firing, they would motion excitedly for me to turn it on to record the noise.

One young resistance fighter, perhaps 15 years old, particularly irritated me by periodically looking at me and gleefully shouting "GHERRAAAM!" in imitation of guerrilla shells hitting their targets.

At one point, in a section distant from guard posts, about a dozen of us walked together through an open area. I wondered aloud to one guerrilla whether we were safe in such a large group. What if the Soviets should be patrolling?

"There are no patrols," he answered confidently. "The Soviets are afraid to come out of their posts at night." If such assurances never quieted my fears, I did not, happily, see them proven wrong. A Ruined Market Town

As towns go, Ghazni was always poor. Now it is a ruin.

A market town, Ghazni drew its life from its position on one of Afghanistan's few paved roads. Even now, its shattered neighborhoods betray its roots in the dry and difficult farm land that surrounds it.

Ghazni's dirt streets and mud-and-straw houses give it the air of an overgrown rural village rather than an urban center. But as in other towns and cities of Afghanistan where the mujaheddin and Soviets have fought with progressively heavier weapons, most of Ghazni's people have fled their shell-torn and bomb-cratered homes, seeking safety in the villages of relatives or in Pakistan.

Still, amid the rubble of neighboring buildings and nightly firefights, people have stayed. At one point as we hurried away from a burst of nearby gunfire, we rounded a corner and almost fell over a toddler -- wearing only a shirt, playing in front of his house while his brother watched, unconcerned, from the doorway.

During most of our time in Ghazni, though, we walked through what seemed an urban moonscape: empty shells of buildings, streets littered with an occasional skeleton of an armored vehicle, and oddly, an old Buick Electra, mounted on blocks, its windows shattered.

As we neared our first destination, the site from which Sanaye would launch his four Chinese missiles, we crossed a small field. To reduce the chances of getting lost, I usually tried to stay near the middle of our file of six, but now I had carelessly let myself fall to the rear.

When red tracer bullets flashed silently across our path, we dropped to the dirt. The sound of the machine gun that had fired them came seconds later, a reminder that bullets travel faster than sound, shattering my illogical, but comforting, assumption that I could rely on a quick reaction to the sound of gunfire to help keep me safe.

The tracers stopped. I crawled forward on belly and elbows to ask my escorting mujaheddin what we should do. When I had gone about 15 yards, I realized that there was no one to ask.

My panic at the idea of being lost was perhaps the only thing that would have convinced me to stand up into the now more dreadful world of silent bullets. I sprinted across the field into a narrow street, where, heart thumping, I found my escorts preparing to dash back to search for me.

Minutes later, we joined the rest of Sanaye's group, which, carrying the heavy four-foot-long missiles, had taken a different route. In a still-inhabited pocket of the town, we stopped at a mosque where two days earlier we had calmly eaten dinner amid the thunder of gunfire and mortars outside.

Now, in the mosque's sanctuary, lit by a kerosene lantern, the guerrillas quickly screwed detonators into the missiles' noses and attached wires for the battery that would ignite their fuel. As they carried the armed missiles down an adjacent street, I climbed a roof to watch their flight.

The missiles, with a reputed range of four to six miles, are a recent addition to the guerrillas' arsenal -- and apparently one of the products of increased U.S. spending on covert arms supplies to the mujaheddin. They are especially convenient in guerrilla warfare: they can be launched from the ground, their trajectory adjusted by stacking stones under their small wooden launching blocks.

With an odd ripping sound, the missiles leaped in pairs from the street. Two incendiary missiles hit in the darkened center of the airport, setting fires, while the two explosive rockets flew over their target entirely, each exploding with a muffled roar and a dull red glow in the hills beyond.

As guns from nearby guard posts began firing into the neighborhood, we hurried away toward Sanaye's next target. After a few minutes' walk, I could hear the rumble of generators powering the lights of the Soviet stronghold, now nearby.

Our pace slowed. We crept more stealthily now, through a maze of streets and buildings, to flatten ourselves against a long wall of packed mud. Sanaye climbed over and, after a few minutes, beckoned us to follow him.

As I threw a leg over the top and slid down the other side, it was clear that we were now in a darkened corner of the lighted Soviet-Afghan government compound. A few moments later, in a shattered mosque nearby, I whispered my question with a calm I did not feel: "Where are we?"

"Khad," a young guerrilla answered, pointing at one of several buildings in the brightly lit and deserted street in front of us.

Khad, a Persian-language acronym for State Information Services, is the Afghan secret police agency, operated under the direct control of the KGB. As the Afghan Army, ridden by desertion and full of mujaheddin informers, proved to be unreliable, the Soviet military has built up Khad as its most dangerous weapon against the resistance. Attack on the Secret Police

If the displays of Soviet firepower in Ghazni suggested their technological advantage in this war, it was Sanaye's attack on the provincial office of Khad that seemed to symbolize the mujaheddin's determined courage, which has prevented the easy Soviet victory predicted by many following their December 1979 invasion.

Pulling two Chinese-made land mines out of a sack, Sanaye smiled at me and asked, "You are not cold, are you?"

"The temperature has not occupied my mind," I answered.

Lacking the Soviets' ability to strike from a safe, long range with artillery or aircraft, Sanaye carried the mines out of the mosque's gate. It seemed like hours later when two explosions roared, apparently from the back of the Khad office.

From somewhere farther inside the compound, we could hear excited shouting in Persian. Mentally I begged the group to leave, certain that we would soon be discovered.

When Sanaye slipped back through the gate, I gratefully shouldered my pack to go, and almost cried out in anguish when he stopped to fire two rounds from a recoilless rifle at the Khad bureau. In immediate response to the bright flash, machine gun fire rattled back in our direction.

We sprinted with the others for the wall of the compound and heaved ourselves over. After a few minutes of bewildering twists and turns, we slowed to a walk in a street some distance from the garrison.

Wondering how it was that the Soviets had not seen us escape, I paid no attention to the soft whistle of the first falling mortar round. The explosion knocked me down and left my ears ringing.

We ran again, and needing no second lessons, I threw myself to the dirt like the others with the warning sound of each new shell. We followed a small teen-aged guerrilla who had lived in Ghazni until a few years ago and who seemed to know every street.

Leaving the mortar attacks behind, we gradually slowed our pace, back toward the edge of the city. Hours later, at about 1 a.m., we reached the trucks that would take us back across the plains.

Ashir, 23, a guerrilla from Kabul, was pleased: among the three groups of mujaheddin, no one had been killed.

"God was with us," he said.

Next: The destruction of the Afghan countryside