If the Kremlin really wants to rout the Afghan guerrillas and "pacify" the country, it will need two to three times the number of troops it now has there -- up to 250,000 men, or more.
That is the view of Western sources here, who see the only other Soviet choice now as maintaining the current troop level (85,000 men in Afghanistan and another 30,000 just inside the Soviet border) and seeing the war against the guerrillas drag on for years.
In any case, the sources see the Soviets maintaining a considerable number of troops in Afghanistan indefinitely. They point to new barracks and officers' clubs being built, among other signs.
Yet the Soviets are allowing the West and the Babrak Karmal government in Kabul to continue to talk of peace and the implications of possible troop pullouts.
Western analysts here see this as a Soviet tactic to try to soften international criticism and minimize the boycott movement aimed at the Moscow Olympic Games in July.
The Kremlin also wants to deflate as much criticism as possible in the muslim world before Islamic foreign ministers meet in Islamabad next month.
"The Soviets are discovering that it is impossible to do more than hold the main Afghan cities with the number of troops they've sent in so far," says one knowledgeable source familiar with Afghan terrain.
"Afghanistan is twice as big as Vietnam in area. The Americans couldn't hold vietnam with half a million men. So far the Soviets have only put 115,000 in the field."
The Soviet ability to keep pouring troops into Afghanistan for a long time to come is not doubted. The question is whether it wants to persevere for so long at such a high cost.
The Soviet press gives no hint that Soviet troops themselves are involved in big operations against the guerrillas. The current Soviet drive with helicopter gunships and troops in the Kunar valley goes unreported.
On April 22, when the official news agency Tass reported that 124 "bandits and mercenaries" had been killed and 47 "terrorists" had surrendered in the Zindajan area, the entire action was attributed to the Afghan Army in Herat.
Us estimates in Washington are that Soviet forces have suffered 8,000 casualties so far.
If Moscow should signal so much as a token withdrawal, pressure would build on President Carter to end his Olympic Games boycott and to relax other retaliation. But the Soviets have sent no such signal.
The International Olympic Committee has been searching for a way out of the US-Soviet impasse but so far without success. The view of the Western community in Moscow is that Soviet troops are in Afghanistan to stay, just as they have stayed in Czechoslovakia and Hungary.
In April the Soviets signed a treaty with the Afghan government laying out the practical arrangements connected with the Soviet troop presence. Moscow signed a similar treaty with Prague after the invasion there in 1968.
"The trouble for the Soviets is that if they withdrew large numbers of troops , the Babrak Karmal government would fall in weeks if not days," says one Western analyst here. "The Soviet invasion itself has increased anti-Soviet sentiment in Afghanistan."
The Soviets made their basic error, it is believed here, back in April 1978 when Nur Muhammad Taraki overthrew President Daoud.
The Soviets thought it had been a radical, historic shift to the left. In fact, Western sources say, it is one more in a long line of bloody coups that have marked Afghan history for centuries.
Now, with Iran in chaos next door, the Soviets have every reason to want to hang on to Afghanistan. At the same time Moscow refuses to discourage diplomatic talk about the future.