Quest for stability in nuclear age. Improved technology makes deterrence more difficult

In the five years since the United States and the Soviet Union concluded the second strategic arms limitation treaty (SALT II), the nuclear arms race has moved into new and potentially troubling areas. Both superpowers have improved their arsenals of destruction. Advanced technology has increased the accuracy, mobility, and stealth of long-range nuclear weapons to where the basis for deterrence -- the certainty of unacceptable retaliation -- is threatened. New developments are moving the possibility of attack into space. Both sides are pushing at treaty limits -- and sometimes exceeding them -- as each seeks advantages and compliance verification grows harder.

This, experts say, could lead to a less stable world, one in which it may well become more difficult to achieve an arms reduction agreement and one in which crises are harder to manage.

The nuclear giants are not the only ones with a stake in this. In opening the UN session on disarmament last month, UN Secretary-General Javier Perez de Cuellar echoed the increasing concern among nations of lesser military might when he said, ``The responsibility assumed by the great powers is now no longer to their populations alone: It is . . . to all of us.''

Similarly, the Aspen Institute International Group (which includes prominent public figures from the US, Western Europe, and Japan) recently warned that behind deterrence ``yawns the atomic abyss.''

``Our fundamental concern . . . is not simply to have fewer weapons or simply to get an agreement with the Soviets,'' Rep. Les Aspin (D) of Wisconsin, a leading congressional figure in military and strategic affairs, told the Chicago Council on Foreign Relations recently. ``Our fundamental concern is to achieve a stable strategic environment, one in which neither side is pushed by fear of suffering a nuclear attack into resorting to nuclear attack first.''

The issue of nuclear stability was the underlying message of the President's Commission on Strategic Forces, chaired by retired Air Force Lt. Gen. Brent Scowcroft.

This panel of experts urged movement away from multi-warhead missiles, especially land-based missiles, which are increasingly threatening yet also vulnerable ``high-value'' targets. Restructuring deterrent arsenals in this direction -- through arms control agreements as well as technological developments -- would be harder for the Soviet Union than for the US, since the Soviets are heavily dependent on land-based intercontinental ballistic missiles (ICBMs).

Meanwhile, since the SALT II talks ended in 1979 new developments in nuclear weaponry have escalated the arms race. This despite the fact that both sides are generally abiding by the accord, even though the US Senate never ratified it.

The Soviet Union is testing its fifth generation of ICBMs, including more reliable solid-fuel missiles. Suspicions about possible SALT violations have been aroused because much of the Soviet missile data is transmitted by secret code.

The Soviets have deployed nearly 400 medium-range SS-20 ballistic missiles targeted against Western Europe and US allies in the Far East. Each missile carries three warheads. Some experts say that by reducing the SS-20 payload, a missile could reach the US itself.

A new long-range strategic bomber -- the Blackjack -- is being tested, and in 1984 the Soviets began deploying long-range cruise missiles on other aircraft. Long-range nuclear cruise missiles are now aboard submarines as well, and the Soviet fleet now includes a new class of very large ballistic-missile-carrying submarine -- the Typhoon.

Western analysts are also concerned that the Soviet Union may be positioning itself to ``break out'' of the Anti-Ballistic Missile Treaty of 1972 with the construction of a large phased-array radar in Siberia and the testing of air defense rockets in an antimissile mode. While cautioning that the Pentagon may be guilty of ``threat inflation'' in describing the Soviet arsenal, William Arkin and Jeffrey Sands, part of a group of experts working on a series of books describing nuclear arsenals, agree that ``a substantial US lead in numbers of warheads can no longer be taken for granted.'' US modernizing its weapons

Defense Secretary Caspar W. Weinberger and other Reagan administration officials give the impression that the US has been fiddling while Soviet weapons builders burned the midnight oil. But in fact the US has been modernizing.

The US Minuteman ICBM was first placed in concrete silos 18 years ago. But since then, its silos have been hardened, its warheads increased, and the accuracy of those warheads improved so that it is more accurate than any Soviet ICBM.

The US strategic submarine fleet is more widely dispersed and more reliable, and warheads on the US Navy's submarine-launched ballistic missiles are much more numerous and accurate than Soviet SLBMs. The Trident II submarine program, featuring very accurate missiles that can attack hardened targets, has been accelerated.

This past year, the US began deploying long-range Tomahawk cruise missiles, with nuclear warheads, at sea. And air-launched cruise missiles with nuclear warheads are now carried on B-52s. New B-1B strategic bombers have begun rolling off production lines, and research on ``stealth'' aircraft and cruise missiles (able to counter enemy radar) has been accelerated.

NATO has begun deploying US-built ground-launched cruise missiles (GLCMs) and Pershing II ballistic missiles in Europe. The Pershing II has a maneuverable warhead, which makes it extremely accurate. And if Pentagon weapons experts are to be believed, the terrain-hugging cruise missile can hit a window in the Kremlin.

While the US considers the new Pershing II and GLCM to be medium-range missiles and not deserving of a Soviet response against the US itself, perceptions in Moscow may be what count. And Soviet leaders believe it irrelevant whether a US missile is launched from South Dakota or England.

The US also has started testing an advanced antisatellite weapon. And it has launched what the Reagan administration calls its Strategic Defense Initiative to research ways to defend against a missile attack using space-based systems. Critics say such a ``star wars'' plan could violate the ABM Treaty, destabilize the strategic balance, and undercut deterrence.

What experts find particularly troubling is the development and deployment of small, mobile, highly accurate nuclear weapons. These are hard to track and therefore likely to proliferate if not controlled by mutual agreement.

``Flight times are getting shorter and accuracy is getting greater, so the time [for] decision in time of crisis is shrinking,'' says William Ury, director of the Nuclear Negotiation Project at the Harvard Law School. ``The thing that concerns me is that the pace of technology is outstripping the pace of the diplomats.'' Two challenging issues

These two issues -- the addition of missile defenses to the strategic equation and the proliferation of easy-to-conceal weapons -- are likely to be the most difficult for US and Soviet negotiators to resolve at Geneva.

Meanwhile, the unratified SALT II treaty expires at year's end, and arms-control advocates are very concerned about what will happen if the arms race proceeds without this agreement. The Federation of American Scientists says that ``in an unconstrained arms race, by 1995 the Soviets could deploy as many as 30,000 ballistic missile warheads and 8,000 bomber-launched cruise missiles.''

``In a quantitative arms race, which is what SALT II controls, there is every reason to think that America will lose,'' the federation warned. ``After all, the United States has trouble siting a few hundred MX missiles while the Soviet Union enjoys civic passivity. We reject overkill while they traditionally favor it. . . . In the end . . . the more determined is likely to win out. . . .''

As for the accelerating developments in strategic technology, the likely outcome of an arms race is less clear. Weapons are becoming smaller, but much more lethal. At the same time, new developments in sensors, information processing, and a more modern hot line could -- in the context of arms reductions and an improved diplomatic atmosphere -- make for a safer world.

``In this pursuit of arms control, we will face both the problems and the opportunities presented by technology,'' observes William Perry, former Pentagon chief of research and engineering, in an Institute for Contemporary Studies paper. ``Our challenge will be to seize the opportunities and overcome the problems.'' Chart: Strategic arsenals US USSR land-based ballistc missiles: 1,026 1,398 Submarine-based ballistc missiles: 648 991 Manned bombers: 310 300 Submarine-launched cruise missiles: 107 120 Source: Federation of American Scientists. -- 30 --{et