Key issue for arms talks -- maintaining stability

``If we both can agree what stability encompasses and move in that direction,'' this would be a major achievement of Soviet-American arms control talks, noted Sam Nunn (D) of Georgia, ranking minority member of the Senate Armed Forces Committee. ``I hope we can reach some conceptual agreements with the Soviet Union.'' Senator Nunn was speaking an hour after the resumption of Soviet-American negotiations March 12, after a hiatus of more than a year. He and other members of the bipartisan Senate and House teams monitoring the talks interpreted positively the clear Soviet priority on proceeding with the negotiations as scheduled despite the death of Konstantin Chernenko.

The two sides agreed to meet again on Thursday in the regular pattern of two sessions per week in the six to-eight week exploratory round. Chief United States negotiator Max M. Kam-pelman said there had been a ``serious and businesslike discussion'' at the first meeting, and chief Soviet negotiator Viktor Karpov made a point of telling reporters that new General Secretary Mikhail Gorbachev presided personally over the Politburo session last Thursday that approved the opening Soviet position.

Nunn's assessment of the initial contact and the overall prospects for the talks is that the Soviets ``are going to have to start thinking'' about the key issue of stability.

``They are being placed in a similar situation to the US,'' he said. ``For some time we have been targets of their SS-18 and SS-19 [heavy missiles with a first-strike potential]. Now our MX and Trident II will be putting them in a similar position.''

Nunn was highlighting the one crucial problem of the nuclear 1980s as articulated by Western strategists -- and increasingly hinted at by Soviet spokesmen as well. That problem is the erosion of political stability through the onward march of technology.

Thus, over the past 40 years the balance of terror has preserved what has come to be termed ``stability'' in Europe -- for longer than has any less apocalyptic standoff in this century. That is, in the region of the world most crucial to both superpowers it has consistently prevented the kind of instability that could lead to war. The potential consequences of trying to foment or benefit from instability have been so horrifying that neither superpower has dared to try to disrupt the other's sphere of influence in Europe.

In the late 1970s, however, this nuclear and political stability was threatened by a potential imbalance of terror. The shift arose from MIRVs -- multiple warheads on single missiles -- and from a gradual ``technology creep'' that dramatically improved missile accuracy.

When the US invented MIRVs, or ``multiple independently targetable reentry vehicles,'' in the early 1970s, this meant that for the first time since both superpowers acquired nuclear weapons, killing an enemy's principal missiles in a surprise attack could pay off -- not politically, of course, but in purely mathematical calculations.

Back in the Model-T age of single warheads and low accuracy in the 1960s, an attacker would have expended several times more of its own missiles than the number of enemy missiles it would have destroyed in any first strike. Two missiles were required to cross-target one adversary missile in any case, and the number of misses would have been high. Any attack would have been senseless; the victim would have had more nuclear weapons left than the attacker after a first strike and could have retaliated with a devastating counterblow.

At the same time that the US introduced MIRVs -- and the Soviet Union caught up in MIRVs in a surprisingly short three years -- accuracies made a quantum leap. A series of incremental improvements in miniaturization, inertial navigation, satellite reconnaissance, and various other physics and engineering fields produced nuclear warheads that approached the 500-foot accuracy at which not even concrete silos super-hardened to resist pressures of 2,000 pounds per square inch could survive. Consequently, there would be far fewer wasted missiles than previously.

Suddenly, then, MIRVs and accuracy together generated a new specter of a ``disabling first strike'' for whoever launched a surprise attack. A single 10-warhead Soviet SS-18 missile, cross-targeted, could theoretically wipe out five US missiles -- and leave Moscow with such a favorable post-strike ratio of Soviet-to-American missiles that Washington would not dare hit back.

To be sure, this possibility was highly theoretical. Neither superpower was likely to bank on the textbook reliability of an untested mass salvo over untested polar trajectories -- or on the rational submission of a devastated adversary that had ``only'' 10 or 30 or 50 percent of its nuclear arsenal left after absorbing the initial attack.

Nonetheless, psychologically the balance of terror was less stable than before.

The US was the first to worry about this state of affairs because of the Soviet advantage in heavy missiles. The Soviet SS-18 was 10 times bigger than the US Minuteman and could carry 30 MIRVs to the Minuteman's three -- if the Soviets so chose and if the restraints written into the SALT II limitations were not observed. Thus, in a first strike every SS-18 could potentially wipe out 15 US missiles -- while every Minuteman could wipe out only 11/2 Soviet missiles.

The disparity between Soviet and US throwweights was the result of deliberate American choice (and superior American miniaturization) rather than any unique Soviet skill -- but this hardly assuaged American concern. As the US had increased its accuracy and decreased the weight of its engines, fuel, guidance systems, and other payloads, it had improved its missiles by making them smaller by several orders of magnitude. The Soviets lagged behind. But once the Soviets, too, acquired MIRVs and caught up to within half a generation of US accuracies, Moscow's old-fashioned heavy missiles turned out to have an advantage. They could launch four times as many warheads as before. The smaller Minuteman could not expand proportionally.

This disparity meant that a Soviet first strike would be far more devastating for the US than an American first strike would be for the Soviet Union. Hence US plans for the MX, the first heavy US missile in a decade. Hence also presidential candidate Ronald Reagan's alarm about a ``window of vulnerability'' in the early or mid-1980s.

Moscow's corresponding alarm would come only later, as the US deployed weapons with potential first-strike accuracies in the late 1980s in its MX ICBMs (land-based intercontinental ballistic missiles) and Trident II SLBMs (submarine-launched ballistic missiles).

The Soviet alarm is more existential than the American, however, since all fixed land-based missiles, whether Soviet or US, are becoming vulnerable to a first strike. This condition is tolerable to the US, which has three-quarters of its strategic warheads on still survivable (because mobile) submarines and airplanes. It is not tolerable to the Soviet Union, which maintains three-quarters of its strategic warheads on those vulnerable ICBMs.

All such speculations take place in a surrealistic world, of course. In the real world it is by now clear that neither superpower would launch a nuclear attack on the other out of mathematical calculation. Indeed, Reagan's bipartisan MX commission conspicuously played down the risks of any Soviet first strike a couple of years ago.

What really worries Americans, however -- and must worry the Russians -- is less a cool, rational, ``strategic instability'' than a hot, impulsive, ``crisis instability.'' That is, in any clash in which the superpowers think their vital interests to be at stake, they might well have itchier trigger fingers now. 2 If mutual assured destruction (MAD) no longer prevails -- if the US and the Soviet Union have no assured second strike capability but stand to suffer much more by failing to ward off the adversary's first strike, there is enormous pressure on them to fire first in a crisis. There is pressure to ``launch on warning,'' no matter how ambiguous the signals of attack. There could even be pressure to initiate a preemptive strike if one side thinks the other is about to do so.

But is this all just Western theorizing, or do the Soviets share the concern? The indications are mixed. Stability as such is anathema to Marxist-Leninist dialectics, which posit a constant change of thesis, antithesis, and synthesis until final, all-encompassing Communist victory in the world. This is vastly different from the West's model of world pluralism, stability of the status quo, and the imperative of not upsetting the existing international order by force.

Yet the nuclear facts of life are crowding in on the Soviets, as they too become theoretically vulnerable to some nuclear first strike by the US.

``I think they have to think in this vein,'' concludes Senator Nunn. ``I think we have reason to think together. More and more we have mutual interests.''