YURI ANDROPOV'S response to President Reagan's "star wars" speech was ironically familiar. The defensive systems against ballistic missiles that the president discussed might appear attractive to the layman, the Soviet leader said, but "those who are conversant in these matters" could not view them in the same way. Implementing Reagan's plan, Andropov said, would "open the floodgates to a runaway race involving all kinds of strategic weapons, both offensive and defensive."

Defense Secretary Caspar Weinberger dismissed Andropov's reply as typical Soviet disinformation, but that characterization seems somewhat unfair. Actually, Andropov's main argument was one that the Soviet leaders learned from America 15 years ago.

In those days Russia spoke about defensive weapons in the same terms President Reagan used 10 days ago. For example, Soviet Premier Alexei Kosygin was asked in 1967 if deployment of a Soviet antimissile system represented a threat to the United States. No, he replied, defensive systems were not "a cause of the arms race, but (were) designed instead to prevent the death of people."

But the Soviet decision to deploy an antiballistic missile (ABM) system around Moscow in the 1960s alarmed Washington, partly because of U.S. anxiety about a new defensive arms race, and partly because U.S. officials feared that if the Soviet Union made itself invulnerable to a U.S. retaliatory strike, it might well be tempted to launch a nuclear attack in some future crisis.

In time Washington convinced Moscow that defensive systems really are dangerous, and in 1972 the two nations signed the ABM treaty outlawing large-scale defensive systems. Perhaps the most convincing U.S. argument was the decision to deploy a U.S. ABM system, but whatever the reason, Moscow got the message. Andropov repeated it in his response to Reagan when he said that a plan to render the U.S.S.R. "unable to deal a retaliatory strike is a bid to disarm the Soviet Union in the face of the U.S. nuclear threat."

In today's world neither the Soviet Union nor the United States can take unilateral action to alter the balance of strategic forces without calculating the response of the other side. For years, America reckoned that the Russians would never be able to match the U.S. strategic arsenal, but this turned out to be just another American miscalculation of Soviet abilities and intentions. In the "star wars" section of his speech on new defensive weapons, Reagan spoke as though the United States could again act unilaterally, but he was wrong, as Andropov tried to remind him.

The Soviet Union would do everything necessary to maintain the existing relationship of parity, Andropov promised. At the same time, his reply seemed to reflect a real anxiety, perhaps because of the memory of earlier U.S. technological challenges.

The Soviet Union entered the nuclear arms race in 1942 when Joseph Stalin learned about British, American and German work on the atomic bomb. He initiated a small Soviet project, which he expanded into an all- out effort when the United States dropped atomic bombs on Hiroshima and Nagasaki. Once the bomb had been shown to work, the Soviet Union had to have it, too.

This determination not to be left behind sprang in part from the traditional Bolshevik urge "to catch up and overtake" the advanced capitalist countries. More specifically, Stalin feared that the atomic bomb had given the United States a huge military-political advantage which the Soviet Union could eliminate only by acquiring a bomb of its own.

When Stalin expanded work on the atomic bomb in 1945, he also initiated an intensive program to develop long-range missiles. The results became evident in 1957, when the first Sputnik caused an internatinal sensation. Khrushchev quickly claimed Soviet superiority, but the rapid expansion of U.S. strategic forces during the Kennedy administration soon destroyed Khruschev's hopes of superiority, or even parity.

Khrushchev's attempt to put missiles in Cuba in 1962 appears now to have been a rather desperate move to augment Soviet strategic power at a time when the United States was moving rapidly ahead. The missile crisis appears to have reinforced Soviet determination not to accept any kind of strategic inferiority. Soviet strategic forces were built up steadily in the 1960s and 1970s and reached formidable levels.

The ABM treaty gave recognition to the fact that no defense could be provided against ballistic missile attack. The Soviet Union had to accept that -- for the time being at least -- the Soviet-American relationship was one of mutual deterrence in which each side is vulnerable to a devastating nuclear strike, even if it strikes first.

This situation has not been wholly to the liking of the Soviet leaders, who have shown no great enthusiasm for a relationship that leaves Soviet security dependent (in the words of one Soviet general) "on the good will of the opponent." But they seem to have accepted the relationship of mutual vulnerability to retaliatory strikes as an objective condition that they must live with.

In the late 1970s Leonid Brezhnev and other Soviet leaders began to spell out a new rationale for their strategic forces that sounded a good deal like the Western notion of "deterrence." These forces, they said, are intended to prevent an attack on the Soviet Union and its allies; any aggressor will receive "a crushing rebuff." The present strategic relationship is one of parity, they claim -- they are not seeking superiority, but neither will they allow America to gain superiority. Nuclear war would be immensely destructive, and it would be suicidal to start one. Brezhnev said more than once that "to try to outstrip each other in the arms race or to expect to win a nuclear war is dangerous madness.''

This rationale has been widely dismissed in the West as disinformation. Surely its practical significance is difficult to assess, especially since "parity" is an elastic term. Moreover, Moscow has not espoused the idea that all it needs is the ability to destroy U.S. cities in a retaliatory strike. It still makes preparations to wage nuclear war, in case it should come to that. But the reformulation of military doctrine does appear to mark a shift in Soviet thinking about nuclear war and the Soviet- U.S. strategic relationship.

While Moscow has been spelling out the deterrent rationale for its forces, the United States has been putting more stress on the war-waging elements in its doctrine. Under the influence of parity the two sides have been converging in their views of nuclear war. Both have a quite schizophrenic attitude to nuclear weapons, seeing them simultaneously as weapons to be used in war and as the agents of catastrophic destruction. There is no evidence to suggest that the Soviet Union has satisfactory answers to the problems of nuclear weapons and nuclear war, any more than the United States has.

The Soviet Union asserts that its strategic relationship with the United States is one of rough parity. The Reagan administration, however, claims that the Soviet Union has a margin of superiority. This claim rests largely on the argument that American ICBMs are vulnerable to a Soviet first strike, now that the latest Soviet ICBMs have multiple warheads and improved accuracy. If the Soviet Union destroyed the Americans ICBMs (so the argument runs), the president would be faced with the choice between doing nothing, or retaliating against Soviet cities, in the knowledge that the Soviet Union could in turn destroy American cities.

There are several reasons, however, for doubting that this scenario looks as promising to Soviet leaders as it looks threatening to the Reagan administration. The Soviets would have to assume that their missiles would function faultlessly, and that the president would not respxpansion ond with bombers and submarine-launched missiles, which carry almost 80 percent of U.S. strategic warheads. There is little evidence in the Soviet leadership of the technological hubris or the political recklessness that would be required to launch the strike envisaged in this scenario.

Nevertheless, Moscow has deployed missiles that could, in theory at least, destroy ICBM silos. Soviet military strategy indicates that if the Soviet leaders believed war was inevitable, they would strike first to break up a U.S. attack before it got off the ground. In such a case Moscow would not be gambling on there being no response (since it would be acting on the assumption that war was about to begin), and the United States would still be able to deliver a devastating retaliatory blow.

Moscow will have its own problem of vulnerability in the late 1980s and early 1990s, when new U.S. systems will be deployed with the capacity to destroy land-based missile silos. This threat -- like the Soviet threat to U.S. silos -- is subject to many technical uncertainties, but in theory it will be serious, because the Soviet Union has about 70 percent of its strategic warheads on land-based missiles (as opposed to about 20 percent for America), and has a much smaller proportion of its ballistic missile submarines on patrol at sea at any given time.

The Soviet Union has undertaken various measures to deal with this threat. It is diversifying its strategic forces; it is putting more warheads on its submarines; it is testing a new solid-fuel ICBM, which may be deployed as a mobile system; it is testing long-range cruise missiles and may deploy some on a new strategic bomber. By 1990 the proportion of strategic warheads on missiles based in silos will have fallen. As both arsenals become more sophisticated, managing the strategic relationship will be a difficult task for both the Soviet Union and the United States. It will be made even more complex by a race to develop new ABM systems.

Although we know in principle that East- West relations are not a zero-sum game -- that one side's loss is not necessarily the other's gain -- we tend to forget it in practice. The world has come to seem more dangerous to us in the West in the last three or four years, but that does not mean that it has become safer for Moscow. The collapse of Soviet-U.S. detente has meant the failure of some of the most important Soviet policies.

Soviet leaders argued that detente resulted from the growth of Soviet power, which had persuaded Western leaders to adopt a more "realistic" attitude to Soviet interests. Strategic parity, they evidently hoped, would be translated into political equality, with beneficial results in trade and technology and in arms control. At the same time they believed their growing military power gave them a new capacity to exploit opportunities to expand their global power and influence.

But Soviet hopes were only partially fulfilled. The growth of Soviet military power and the assertiveness of Soviet policy, far from strengthening detente, undermined it and helped to push the Soviet Union's chief adversaries closer together. By the end of 1978 the Russians were becoming anxious about a quasi-alliance of the United States, China, Western Europe and Japan. In June 1980 Marshal Nikolai Ogarkov, chief of the general staff, warned that these countries were trying to form an anti-Soviet front "in which the military might of the U.S.A. and the European countries of NATO in the West would be united with the manpower resources of China and the industrial potential of Japan in the East."

Moscow has tried to prevent the strengthening of this potential alliance. Andropov has continued the policy of seeking improved relations with Western Europe and China, though so far without conspicuous success.

The talks on medium-range nuclear weapons based in Europe, now going on in Geneva, have become a central focus of Soviet-U.S. rivalry. The two sides view the balance of nuclear forces in Europe in veryon different ways. Moscow claims that parity exists and that NATO will upset that balance if it proceeds with its plan to start deploying new U.S. missiles in Western Europe in December. Washington claims the deployment is essential to redress an existing imbalance.

Two considerations influence the Soviet position. First, the Soviet Union has traditionally regarded U.S. systems that can strike Soviet territory from bases in Europe as strategic. Consequently, it sees the new U.S. missiles not only in terms of the European balance but also as an addition to U.S. strategic power. It has shown special concern about the Pershing II, which (if it performs to specification) will be able to destroy hardened targets in the Soviet Union.

Second, alongside the criterion of Soviet- American parity, the Soviet Union invokes the principle of "equal security." This means that it wants to take account of British, French and Chinese systems, on the ground that these are aimed at the Soviet Union. Consequently, it wants an agreement limited to Europe, and it wants British and French forces counted on the Western side.

Reagan's new offer of an interim agreement with equal numbers of warheads on Soviet and U.S. land-based intermediate-range missiles, "on a global basis," will not satisfy the Soviet conditions. NATO would still deploy the Pershing II; British and French forces would not be counted; and no allowance would be made for the Sino-Soviet nuclear balance.

The Soviet Union does have a clear incentive to reach an agreement to forestall, or at least to limit, deployment of the new systems, since it must fear that if they are deployed without restriction they will later be augmented, or upgraded. But it will take hard bargaining to reach an agreement.

The Soviet Union may now be at a turning point. It faces difficult economic problems at home. Its detente policy has had very limited success, but no new line of foreign policy has emerged. Soviet thinking about nuclear war has been going through a period of change. The political succession -- a process that is still going on -- provides the opportunity to define new priorities and policy directions. It would be foolish to suppose that Western governments can determine the choices the Soviet leaders make. But Western policy will be a major factor in Soviet decisions.

The Reagan administration has made plain its willingness to confront Soviet power and challenge it to more intense competition. If that is the choice the Soviet leaders face, the history of the arms race suggests that they will take up the challenge and that they will be able to meet it. The United States has staked its security on its superior technology before, but the Soviet Union has stayed in the race, sometimes -- as with multiple warheads -- catching up more quickly than expected.

If the Soviet Union is at a turning point, America should show itself ready not only for competition, but also for cooperation. This does not mean acceding to all Soviet claims, but it does mean setting out the basis for a cooperative relationship, something Reagan has never done. Moscow may not choose that course, but the West should not close off the possibility by denying it the choice.

Western governments have found the Soviet Union to be, at best, an extremely difficult partner in international relations. The Soviet Union is a very powerful state, with global ambitions. Its leaders have been very sensitive about Soviet security but oblivious to the security interests of other countries. They have been secretive and ruthless in their foreign policy. But still the problem of dealing with the Soviet Union has to be faced.

What is troubling about President Reagan's plan to develop defensive systems is not only that it may precipitate a dangerous round in the arms race. It also looks like an attempt to wish away the problem of the Soviet Union, and thus like an abnegation of the responsibilities of statesmanship.