There are those who say the Soviet invasion of Afghanistan does not represent anything new in Soviet behavior. They see this as just one more natural step on the Soviet road of expansionism and imperialism. The change, they say, is in the Western perceptions about Soviet policies, especially on the part of those who did not expect this Soviet move. I would like to suggest, however, that the invasion of Afghanistan signifies a major change not only in western perceptions of Soviet policies but also in Soviet perceptions and behavior.

During the past 15 years, the Soviet Union succeeded in achieving strategic parity with the United States and in envolving into a global military power. The major thrust and concern of Soviet international policies in the Brezhnev era were how to translate successfully the new Soviet military power into political power and influence in the international arena while avoiding a direct confrontation with the other super-power, the United states. In the last few years, Soviet behavior has become more assertive and dangerous, as illustrated by Soviet adventures in Angola and Ethiopia, and by the use of military proxies to further Soviet interests.

However, the Soviet decision to invade Afghanistan constitutes a watershed, a qualitatively different step in acquiring political power abroad by military means. For the first time, the Soviet Union used its own military forces on a massive scale outside its own satellite empire -- the sphere of influence that the Soviets acquired as spoils of victory after World War II. This in itself indicates a new degree of confidence, self-assertiveness and expansionism that would necessitate major reassessment and countermeasures on the part of the Western alliance.

Equally important, however, are the reasons behind the decision to invade Afghanistan. In my opinion, these can be found in a reordering of priorities and in changes in the assumptions that underlay the policies of the Kremlin until now. The key Soviet priority has been to keep a balance between their desire and need to prevent a drift toward a major war or a dangerous confrontation with the United States and their appetite for new international spoils.

These priorities have been upset. The assumptions on which the Soviets acted for a long time were that they ahd much to hope for from a cooperative relationship with the West, and especially with the United States, and that they had much to fear from the United States if their behavior became too adventurous. These assumptions have now been dismissed.

It would be easy and very reassuring to assume that the Soviet leadership has made a miscalculation in its Afghanistan decision, that it did not anticipate the American reaction that has already occurred or that it did not consider the long-range implications for the Soviet relationship with the United States. I cannot for one moment think that this was the case. From everything that is known about Soviet decision-making, one can only assume that the Afghan decision was taken in a careful and deliberate process during which the pros and cons were closely examined.

In the long run, of course, it may happen -- as it has often happened in the past -- that Soviet greed will be proven a poor guide and that the long-term reactions of the West will turn the decision into a miscalculation. Nevertheless, the decision itself was carefully weighed, and the assumptions and reordering of priorities that are hidden behind the decisions are most disturbing.

In analyzing Soviet international behavior, we are accustomed to saying that the Soviet leadership usually engages in low-risk and low-cost operations. It may well be that from the Kremlin's perspective, the Afghanistan action also meets these criteria. If this is so, then the Soviets have undertaken a major redefinition of what "low risk" and "low cost" mean.

Why have such a reordering of priorities and redefinition of assumptions taken place?

Because the Soviets apparently consider that the relations of international force, and especially of international military power, have changed drastically in their favor.

Because they see as compromised the American long-term resolve to counteract Soviet expansionism.

Because they see the new turmoil that envelops many Third World regions, and at which the West is forced to look helplessly, as a rare opportunity for Soviet advancement that they are afraid and impatient to let slip by.

Because, however much they may need Western technology, know-how and credits, they were disappointed by the degree of cooperation in this area with the United States, and they feel as well that Japan, Germany and other industrial Western allies will not follow the American examples in denying the Soviets high technology.

Because they felt, on the one hand, that the SALT agreement was already dead and, on the other hand, that the United States and its allies will have no choice but to resume arms-control negotiations after a decent interval.

Soviet behavior in Aghanistan creates a new danger of successful Soviet adventurism in the Middle East. The current Iranian non-government may not last long. The Iranian revolution may well, and probably will, evolve toward the left. The Soviets are now well poised to exploit such a development in a country of infinitely greater importance than Afghanistan.

It is pure wishful thinking to see a Soviet Vietnam developing in Afghanistan. The massive and decisive use of Soviet military power almost inevitably ensures them the necessary control over the country. The guerrillas fighting in the mountains will probably not be eradicated for a long time. But the Soviets will have enough control to maintain the puppet regime in power. After all, they have the experience of fighting with much less power their own Moslem guerrillas, the Basmachi of Central Asia, for over a decade.

One can be sure of one thing: in a few months' time, after the Afghan dust has settled, new and enticing peace overtures will come from Moscow; let by-gones be bygones, and let us start again, will be the theme. When we start talking with the Russians again -- and talk we must -- when we again start to look for ways to regulate the conflict and to search for areas of agreement and cooperation -- and look we must -- let our first priority be to convince the Russians that their recent priorities and assumptions are as dangerous for them as they are for us. Let us convince them that, indeed, they have a lot to hope for and a lot to fear from the United States.