Soviets prepared for a long fight in Afghanistan

In Afghanistan, the yearly April offensive of the Red Army has become as predictable as spring. Just as predictably, defiant mujahideen guerrillas seem ready to take the punishment - and bounce back to harass Soviet troops propping up the regime of Babrak Karmal.

Now, more than three years after the Red Army first occupied Afghanistan, there are hints of a difference. These are strong enough to suggest that Yuri Andropov has already put a distinctive ''carrot and stick'' stamp on Soviet Afghan policy:

* The Soviet military buildup at Kabul, at the Bagram airport some 40 miles to the north, and at Kandahar seems bigger than preparations for previous spring campaigns. Already there are reports of stepped-up fighting in areas along the Pakistan border, as Soviet forces seek to limit the flow of supplies reaching the rebels from outside. All this suggests the Soviets this year plan to confront the guerrillas with an extra-potent ''stick.''

* A Soviet policy of holding out the ''carrot'' of negotiations has been dusted off; there were similar hints under Mr. Brezhnev. The attention Mr. Andropov gave to Pakistan's President Zia at Brezhnev's funeral in Moscow spotlighted this ''carrot.'' The ostensible Soviet support for UN Secretary-General Javier Perez de Cuellar's efforts toward a negotiated solution also fit this approach, although the Soviets deny they are involved in the UN-sponsored indirect talks between Pakistan and Afghanistan.

* Soviet forces are reported to be relying increasingly on ''KGB-style'' tactics, such as encouraging jealousies among rival guerrilla commanders and making deals with those who may be enticed to seek Soviet aid against their rivals.

In a different vein, speculation that Mr. Andropov might want to negotiate a way out of Afghanistan has been fueled by rumors that while KGB chief he had opposed the Soviet invasion of December l979.

Just what are Soviet intentions? ''They are doing the same thing as the insurgents,'' says Mohammad Homayoon, a Cambridge-based Afghan who sympathizes with the insurgents. Mr. Homayoon, who says he maintains close ties with friends and relatives in Kabul, says each side is trying to escalate the fighting and casualties so the other side will find negotiations more attractive.

One question is whether more fighting will, in fact, bring a preference for negotiations - or instead a growing bitterness that bars compromise. ''The guerrilla leaders must come to understand that no Soviet leader concerned about Soviet security can accept an Afghan government unfriendly to the Soviet Union, '' explains Mr. Homayoon. ''If the guerrilla leaders are unable to accept this, I hope supporters such as the United States and Pakistan will help them understand.''

So far there appears no concrete reason to think present Soviet tactics - either the carrot or the stick - will quickly end the war. Amid the Soviet buildup, the guerrillas have stepped up their own attacks. These include bombings in Kabul and attacks on both electricity and natural gas installations. The guerrillas appear to be raising their sights to city targets, rather than confining themselves to Afghan or Soviet country outposts. Homayoon claims, ''They have demonstrated their ability to stand up to the Soviet army. They are stronger today than two years ago.''

For the Soviets the cost, estimated by some as high as $10 million a day ($3. 5 billion a year), is dear. One Western source describes the situation as a ''standoff'' - rather than a stalemate. Thus each side retains the capacity to conduct operations and sustain casualties, but until now neither has demonstrated the ability to administer a ''knockout'' blow.

A view held by some Western diplomats is that the Soviets have dug in for the ''long haul,'' in an effort to find the most effective, affordable way to keep Afghanistan in the Soviet orbit. The minimum objective is to prevent the collapse of the Karmal government. The Moscow military strategy may well be compatible with the eventual negotiations. But, as of now, it appears that Moscow will aim to buttress its bargaining position with a military ''position of strength'' that requires any future Afghan government to be friendly toward the Soviet Union.

This Soviet objective is likely to be justified in Moscow both defensively and offensively. The Soviet Union has long been committed to preventing a repetition of the post-World War I cordon sanitairem in which neighboring governments sought to stir up resistance in the Soviet Union against Lenin's Bolsheviks. Some observers, including Mohammad Homayoon, suggest that Moscow is similarly concerned that if Muslim fundamentalists come to power in Afghanistan, this might stir up discontent among Muslims in the southern regions of the Soviet Union.

The Soviet Union also looks to Afghanistan for raw materials, including natural gas. There has been speculation, too, that Moscow seeks missile bases in Afghanistan within range of the Strait of Hormuz. Finally, there are concerns the Soviets might use a presence in Afghanistan to threaten subversion in the Pakistani province of Baluchistan.

Here are some of the signs cited by those who suggest the Kremlin is committed to a favorable outcome:

1. Feature-length stories in the Soviet press seem to be preparing the Soviet public for a long stay and continuing casualties. Rather than veiling the military's Afghan assignment in secrecy and fabrications, as during the first years of occupation, recent coverage of the Soviet army's military and alleged development role in Afghanistan has seemed aimed at winning public understanding and acceptance.

2. Active, direct Soviet participation in Afghan government, including 3,000 to 5,000 Soviet advisers. About 2,000 Afghans are said to be sent to the Soviet Union each year for training, with an estimated 10,000 studying there now. The aim appears to be creatation of a loyal group of administrators, which would insure a high degree of Soviet influence in Afghan governments for some time to come.

3. The decline due to desertions of the Soviet-backed Afghan Army, which is down to perhaps as few as 40,000 men from a former strength of 100,000. There were some 10,000 desertions in l982, according to a Western source. This means Moscow would risk a major collapse if it tried to withdraw Soviet troops and turn the fighting over to Afghans.

4. A limited military commitment of some 105,000 Soviet soldiers. This is said to permit only one large operation at a time, since troops must also be committed to garrison duty and convoy support. This relatively small force may reflect Moscow's desire to keep the military and economic drain to a level low enough to be sustained over a number of years.

In line with this limited presence, Moscow appears to have refrained from an attempt to seize and hold Afghanistan's vast rural areas. Forays into the countryside have often been limited to punitive search-and-destroy missions designed to attack guerrilla forces, and to destroy cities and villages sympathetic to the rebels. Although Soviet units have sometimes been stationed in rural areas to decoy and trap guerrillas, the active Soviet presence has so far concentrated on urban areas such as Kabul.