The Soviet military, in its first sustained test under fire since the end of World War II 35 years ago, has shown itself to be inflexible and slow to respond to Afghanistan's spreading popular revolt, according to observers here.

While its field performance is being questioned, some of the Red Army's new, top-of-the-line equipment, being tested in combat for the first time, is viewed as superior to anything the West has to offer, according to Western, Asian and East European diplomats interviewed here last week.

This is especially true of the M124 helicopter gunship, which has proved to be the Soviets' most successful weapon against rebels challenging the Soviet-backed government of President Babrak Karmal. Similar plaudits are given the wide variety of armored vehicles in use here that are crosses between light tanks and armored personnel carriers.

The M124 regarded as the best armored helicopter gunship in the world. The U.S. version of the troop-carrying light tank is years from being included in America's military arsenal.

Nonetheless, after their initial success in moving 80,000 troops into this country quickly, a feat that was watched with awe by observers here, the Soviet forces appear to have bogged down.

They get low marks for their ability to respond to the crazy-quilt pattern of attacks here. The sources of uncoordinated rebel bands seemingly strike convoys and Afghan government installations at will.

While the Soviets forces have not been beaten by the Afghan insurgents, neither have the rebels been subdued by their vastly better equipped and far more numerous foes.

As the Americans did in Vietnam, the Soviet military here is using body counts to show superiors at home that they are winning the battle against the insurgent forces, according to Western, Asian and East European diplomats here.

These body counts reportedly are as exaggerated as those of Soviet losses put out by rebels based in the Pakistan city of Peshawar, just across the border on the other side of the Khyber Pass.

"They probably believe those body counts just as the U.S. officials did in Vietnam. They probably think they are defeating these guys. But the rebels keep getting clobbered and they keep coming back for more," said one observer.

Moreover, in the almost eight months since the Soviets invaded Afghanistan, the rebels have improved their tactics, according to experienced observers. For example, they have become adept at planting land mines in the already pitted and rut-filled roads, often destroying Soviet armor.

Early last week, for example, three burned-out Soviet armored personnel carriers were trucked through Kabul. Those who saw them said it is unlikely the hulks will see combat again.

"I've lost my awe of the great Russian bear," said one Western observer. "They are always slow to respond. Their morning attacks are always planned the night before and it sometimes takes them a day or two to move against the insurgents. There are no hunting operations of the sort the Americans ran in Vietnam."

Furthermore, the disunity of the rebels appears to have become a strategic advantage for them. Since there is little or no coordination between the different insurgent groups, it is more difficult for the Soviet forces to plan any coherent line of attack.

"There is an uprising in Badakhsan and they rush up there. Then something happens in Ghazni and they have to race there. They can't seem to mount more than one operation at a time and they never are able to clean up an area," said a Western diplomat here.

"They are just running themselves ragged trying to fight something like the rebels," he continued.

What is needed, Western and Asian analysts here agree, is a more flexible military command structure that gives authority to officers in the field. But that runs counter to the entire Soviet military concept of highly centralized commands.

"No colonel has any experience taking the initiative," said one analyst.

Thus, a highly mechanized and well-equipped Soviet force of close to 100,000 troops has been unable to stop bands of rebel fighters that most diplomats here think hardly number 15,000 -- although the rebels appear to have the full support of the vast majority of the population. The rebels are armed largely with captured weapons or the ancient British Lee Enfield rifle, which is considered a very good sharpshooter's weapon.

With their superior arms, the Soviets should be able to do better, most observers say. They have an enormous arsenal scattered around the country. There reportedly are about 60 Mig 21 jet fighters in Afghanistan, plus others at bases just over the border in the Soviet Union.Besides the Migs, a squadron of SU17 fighter bombers, designed for penetration attacks, is said to be at a Soviet air base in Basgharam, northeast of Kabul.

There are an estimated 175 helicpters in the country, including 70 to 80 MI24s, which carry 224 rockets in four side pods and have either a machine gun or a cannon in the front. The helicopter gunship has two tracks for antitank weapons, but they are not needed here since the rebels have no mechanized armour.

The MI24, said to cost up to $3 million, is described as an awesome sight in action. It was used in combat for the first time, just one year ago to put down a mutiny of Afghan troops stationed at the historic fort of Bala Hissar, which stands 400 feet above the plains of Kabul. It is still not known whether the MI24s were flown then by Afghan pilots or by the Soviets who until September were in the country as "advisers."

"The MI24s are damned good -- a real ace in the hole for the Soviets. We expect to see more of them," said one observer.

Diplomats who have watched the M124 in combat around Kabul have noted that the Soviets tend to go in very low with them and use them stricltly as man-killers.

If the Americans had flown their helicopter gunships that low in Vietnam, said one observer, the aircraft would have been peppered with shells. The rebels have few good anti-aircraft weapons, however, although there are reports of a few hand-held surface-to-air missiles (SAMs) appearing in rebel units.

If those reports are true, the SAMs are likely to have been supplied from outside the country since the Afghan Army, the major source of sophisticated weapons for the rebels, has mostly large truck-pulled SAMs. The few hand-held SAMs in the Afghan Army arsenal reportedly were pulled back to Kabul to keep them from falling into rebel hands.

The Soviets have lost about 100 air-craft, according to estimates here, but it is unclear how many were crashes caused by malfunctions and how many were due to rebel fire.

Despite the lack of sophisticated antiaircraft weapons, analysts here say the rebels have managed to down some of the Soviet air amada, including two heavily protected MI24s. Last week alone, according to one usually reliable source here, three Soviet helicopters, probably troop-carrying MI8s, crashed in the Grazni area, where an Afghan division equipped with SAMs had rebelled. Observers here believe those three helicopters probably were shot down during a massive Soviet operation to put down the Afghan Army mutiny.

Afghanistan does not offer good terrain for tank warfare, and the Soviets appear to have withdrawn most of their big tanks. Of those that remain, reportedly about 300, most are dug into stationary artillery positions.

But there are thousands of armored personnel carriers (APCs) in Afghanistan -- far too many for observers to keep track of -- and they are the main-stays of the Soviet ground offensive.

The APCs are in effect light tanks that carry a squad of infantrymen. One has a large cannon on top and gunports along the side from which the infantrymen fire.

American versions of this kind of fighting vehicle are just coming off the drawing boards and are not in production yet.

In Kabul, the massive Soviet presence can be seen at the civilian air-field, which now has become a major military base with lines of helicopters and Migs alongside the main runway. The Soviets have set up four inflatable buildings as maintenance hangars.

Soviet troops and armor are billeted all around the city. They are in Bala Hissar Fort and behind a former royal palace which has been taken over as the Soviet military headquarters. There is a massive display of Soviet armor on the hills of Khair Khana (the Kindness Pass), where permanent installations are taking the place of tents. There are signs that the Soviets are digging wells for water in the hillsides.

Every night at about 6:30, some 60 Soviet troops billeted in the Arg -- a collection of Afghan government ministries on the grounds of what is now known as the People's Palace in the center of Kabul -- shape up for their evening patrols. After receiving their orders for the night, the Soviet troops march off in a ragged band.

"They look like they are in the first week of basic training, and they are supposed to be the elite troops," said a man who has watched the formation.

In the city, the Soviets ride around in the APCs, wearing a summer uniform that includes a wide-brimmed hat that looks as though it belongs on a Teddy Roosevelt Roughrider.

They appear arrogant as they push past traffic. One shook his fist at a diplomat who has the temerity to pass a convoy. An officer cooly pointed his pistol at me one day last week as he rode past standing up in the hatch of an APC.

Many of the Soviets ride around Kabul in vehicles clearly marked with a red cross, a violation of international law since ambulances and other Red Cross-marked vehicles are supposed to be used only for carrying the sick and wounded. In Kabul, however, the Soviets apparently use ambulances as logistical vehicles.

All of the supplies for the massive Soviet war machine come from the Soviet Union, either by truck convoy or in an airlift.

Frequent Soviet flights in and out of Kabul either bring supplies or transfer them to Army posts in different parts of the country.

While some of the planes are clearly military, others carry the markings of Aeroflot, the national Soviet civilian airline.

Much of the material brought in by road is carried on trucks built in a plant set up with the technical assistance of the Ford Motor Co. Even though the Soviet contract with Ford specified that the Kamaz trucks were not to be used for military purposes outside the Soviet Union, they are seen daily on the streets of Kabul carrying supplies for the Soviet troops in Afghanistan.

One of the favorite occupations of diplomats here is trying to estimate the cost of the Soviet military adventure. While it has proved to be an impossible calculation, many believe a rough figure would be about $10 million a day.