The weapons come in fits and starts. Sometimes a caravan of 30 or 40 packhorses weaves its way northward through the mountains, well-stocked with sophisticated weapons.
At other times, groups of Afghan guerrillas returning from Pakistan will only be shouldering rifles, most of them dating back to World War II.
The question of getting foreign military assistance to Afghan guerrillas fighting the nearly five-year Soviet occupation is one shrouded with cloak-and-dagger secrecy and plagued by political manipulation and poor planning.
This is the case not only with the suppliers, such as the United States, certain Persian Gulf nations, and China, but also with Pakistan, through which most of these outside arms are channeled, and the Afghans themselves.
The mujahideen (holy warriors) seem to have enough small arms, even if some are ancient. But the guerrillas themselves and Westerners who have managed to travel with them inside Afghanistan say the resistance needs more appropriate, sophisticated weaponry. Above all, it needs better training to conduct a sustained guerrilla war.
Despite assurances by United States government sources that the Central Intelligence Agency has provided at least $325 million worth of military assistance since the invasion, Congress passed a resolution in June calling for more effective aid to the Afghans.
There seems little doubt that American, Arab, and other funds are being used to furnish weapons to the resistance. But how many actually make it to the interior is another matter.
Many of these arms are purchased in third countries such as China and then shipped to the port of Karachi in Pakistan. Some shipments are reportedly dispatched by air to Islamabad, the Pakistani capital.
A much smaller quantity is supplied directly to the mujahideen - most of whom are radical Shiite Muslims - by the Tehran government across the Iranian-Afghan border.
Once on Pakistani soil, the arms are trucked to Peshawar near the Afghan border, where they are stocked and gradually distributed to the Afghan political parties, mainly the fundamentalists. Although the Pakistanis deny any complicity in furnishing arms to the resistance, they keep a close eye on all movements, preferring to allow only a trickle of heavy, more sophisticated weapons to enter Afghanistan.
As a ''front line'' state, Pakistan seeks to avoid provoking the Soviets. The US has refused to provide the regime of Gen. Zia ul-Haq with guarantees that it will come to its assistance in the event of a major Soviet attack.
Moscow has brought heavy pressure on the Pakistanis to curb resistance activities, in particular supply caravans.
Many weapons never get beyond the frontier. Curiously enough, the arsenals of Pakistani Army and police forces in Pakistan's Northwest Frontier province have undergone striking changes. Since the invasion, their weapons have tended to reflect the types brought ostensibly for the Afghan resistance. On the other hand, numerous old Pakistani Army rifles, some still sporting registration numbers, have been finding their way into guerrilla hands.
The Pakistanis have not been the only ones to control the weapons to their advantage. Many a corrupt member of the Afghan exile parties has made a tidy sum selling arms on the black market rather than passing them on to the inside.
Yet even when the weapons finally make it to the frontier, they are not necessarily handed over free of charge by the parties to the mujahideen. Transport costs are also high.
Furthermore, some resistance fronts such as the Islamic State of Nooristan regularly confiscate weapons from returning mujahideen either for themselves or to sell in Pakistan.
Apart from distribution problems, a substantial portion of the weapons supplied to the resistance is simply not appropriate.
Soviet-made SAM-7 (surface-to-air) missiles, which are known to have a disastrously high malfunction rate and are thus practically useless in the field , are still the only type of missile supplied to the resistance.
In addition, the SAM-7s leave a telltale trail of white smoke, enabling pilots to identify the firing position easily.
Most of the Soviet aircraft that have been shot down appear to have been hit by heavy machine-gun fire rather than SAMs. Yet while most guerrilla groups have at least one or two dashakas (heavy machine guns), ammunition is in short supply.
Another complaint is that the medium-range mortar available here - the 82mm - not only has a poor range but also a dangerously high misfire rate, leading many commanders to refuse them.
A more effective military aid program would not necessarily cost more money, advocates of the resistance say. Perhaps what is most needed, they suggest, is a proper distribution network with aid going directly to the interior with as little involvement by the Pakistanis as possible.
Such advocates also argue for a more rational selection of weaponry. Flooding the resistance with antiaircraft missiles or other sophisticated weaponry is not going to solve any problems. Most of Afghanistan's 200-odd guerrilla fronts do not have any expertise in operating anything more complicated than a rifle.
''The resistance should only receive what it can handle,'' noted a military observer.
''But then, whatever is given should be tough and effective.''
But what the resistance needs more than anything else for the moment is proper training. This, it is suggested, should be provided either in a third, preferably Muslim, country or inside Afghanistan itself.
More attention should be paid to the basic essentials that help a guerrilla force perform well in difficult conditions: mine detectors and radios as well as anoraks, boots, sleeping bags, and other forms of outdoor gear.
Advocates of the resistance say that the Afghan guerrillas should learn that while they may depend on outside help, they must retain their own initiative.