The Reagan administration finally appears ready to offer a proposal designed to break the deadlock in US-Soviet negotiations on reducing intermediate-range nuclear missiles in Europe. Although continuing to support the ''zero-option'' as his ultimate goal, the President will likely propose an interim agreement allowing both sides to deploy a limited number of missiles until they are banned completely.
Compared with the simplicity of the President's zero-option plan, which calls for a ban on over 600 Soviet missiles in exchange for US agreement not to deploy 108 Pershing II and 464 cruise missiles in Europe, arriving at an interim deployment level appears more complex. This is especially so because each nation has deployed intermediate-range missiles with different motivations in mind.
How then should we view the choice of intermediate-range deployment levels? Rather than selecting an interim level based on political judgments, a more meaningful military criterion should be used to arrive at missile limits that could well become permanent. We suggest the maximum deployment of Soviet missiles should be a comfortable percentage below what Russian military planners see as their minimum essential need.
Why is this approach important and how does one arrive at estimating basic Soviet needs?
First off, the Soviet approach to developing and deploying intermediate-range nuclear forces differs greatly from the US approach. American decisions regarding weapons like the Pershing II and the ground-launched cruise missile were driven largely by political considerations. The most prominent was the need for a concerted NATO response to an aggressive Soviet SS-20 deployment. Indeed, NATO's proposed numbers of Pershings and cruise missiles (572) bear no close relationship to military targeting requirements.
The USSR, in marked contrast, bases its need for specific numbers of intermediate-range missiles on an assessment of the unique targeting demands in the various geographic regions arrayed along its borders. Requirements for missiles are based on a calculation of the number of enemy targets in these peripheral theaters, the nature of the targets, and, finally, the expected reliability of weapons to destroy their intended targets.
Currently, the Soviets have some 514 intermediate-range missiles trained on Western Europe. The 280 SS-4s and SS-5s are rapidly approaching obsolescence but are probably being held as bargaining chips for the Geneva talks. This leaves some 234 modern, mobile, MIRVed SS-20s, the weapons of most concern to the US and its NATO allies.
For SS-20 units capable of striking Western Europe, Soviet defense planners must consider targets not only within the NATO area, but the Near East and Middle East theaters as well. There are probably 1,000 targets of interest to the Soviets in these regions, roughly 300 of which are ''time-urgent.'' According to Soviet military writings, time-urgent targets - nuclear weapons, installations supporting nuclear weapons, and defensive targets such as surface-to-air missiles or early warning radars - must be destroyed immediately when the decision is made to escalate to nuclear warfare. Ballistic missiles, not slower reacting aircraft, are needed to attack these highest priority targets.
Most of these time-urgent targets would be considered ''soft'' - not significantly hardened against the effects of a nuclear blast. Being soft and mostly stationary, the vast majority could be effectively destroyed with one warhead per target. For hardened and large-area targets, nuclear-armed aircraft could perform follow-up missions. From a Soviet planner's perspective, roughly 300 SS-20 warheads would thus appear essential to deal with just the highest priority time-urgent targets.
Realistically, a Soviet military planner must assume some degree of unreliability in SS-20 operations. A safe assumption is that 80 percent of the total can effectively reach and destroy their targets. The Soviets then need 375 warheads, or 125 SS-20 missiles (each with three independently targetable warheads), to ensure having 300 effective warheads for time-urgent targets.
How do these calculations of basic Soviet military needs stack up against Moscow's recent arms control initiatives? Last December Soviet leader Yuri Andropov proposed to reduce the SS-20 force arrayed against NATO to 162 missiles , in exchange for no deployment of Pershings and cruise missiles. The rationale for retaining 162 missiles, so claim Soviet writers, is simply to balance British and French missile deployments of around the same number. In fact, the Soviet choice of 162 is more likely derived from their basic military requirement for SS-20s.
With a better understanding of Soviet SS-20 deployment motivations in mind, the US should consider countering the Andropov proposal with a ceiling of around 100 missiles for each side. Such a cap would reduce Soviet missile numbers a comfortable percentage below what they probably believe is their minimum essential need (125 missiles).
To be sure, this approach requires further study. But the method - viewing the problem through Soviet eyes - is fundamental to achieving meaningful arms control. Although a common ceiling of 100 intermediate-range missiles gives the Soviets a three-to-one warhead advantage, French and British nuclear forces tend to balance this asymmetry.
This proposal does not address the problem of refire missiles (either Soviet or US), but refires have utility against the time-urgent targets that determine minimum deployment requirements. This method can also be applied to SS-20s based in the Far East to arrive at deployment levels acceptable to American allies in the western Pacific region.
In the end, if the US can achieve reductions to these levels, the merits would go beyond a historic drop in Soviet intermediate-range missile levels to a more important barometer of arms stability - that of injecting uncertainty into Soviet war planning. And such uncertainty lies at the heart of NATO's principal raison d'etre - the deterrence of war.