Moving away from mobile missiles: a feasible proposal

ONE provision of the arms control proposal the United States has put forth in Geneva is a ban on all mobile, land-based intercontinental ballistic missiles (ICBMs). It is a provision the Soviets are almost certain to reject. If and when they do, we should propose that each side be allowed to deploy mobile missiles so long as they are limited not simply in number but in what they can carry and where they can roam. Such an approach would meet the twin criteria of being both negotiable and desirable; the current proposal does neither.

Almost all the long-range missiles in the arsenals of both superpowers are based in fixed concrete silos. The missiles of each are thus vulnerable to the others' powerful and increasingly accurate nuclear warheads. A relatively small number of Soviet missiles, each with substantial numbers of independent warheads, could destroy most and possibly all of US land-based missiles.

Largely for this reason the President's Commission on Strategic Forces suggested that the US proceed with development of a single-warhead mobile missile. It would pose no first strike threat to Soviet missiles (it makes little sense to use up one missile to destroy one missile) and, owing to its mobility, would itself be less vulnerable to Soviet attack.

Why has the Reagan administration rejected these arguments and proposed a total ban on mobile ICBMs?

Not that long ago the administration endorsed mobile missiles when it was thought they would be relatively inexpensive and when it appeared Congress would only fund the MX in exchange for administration support of the proposed Midgetman single-warhead mobile missile. Now Midgetman costs are skyrocketing and Congress will fund only 50 MXs; for many in the executive branch this is too much to pay for too little. Moreover, it will likely be the next decade before Midgetman is ready to be launched, and then

only if the bugs can be worked out and Congress does not have a change of heart.

The Soviets are already fielding a single-warhead mobile missile of their own (the SS-25) and are developing a multiple-warhead (10 atop each) mobile missile (the SS-24), which would move on rails. The argument is simple: Why not ban what they have and we do not?

Opposition to mobiles also stems from concern over verification. Were a new arms control treaty to be negotiated, would we be able to demonstrate to our own satisfaction that the Soviets were deploying no more mobile missiles than permitted?

The dilemma is obvious. The characteristic that makes a mobile missile desirable -- its ability to move thereby complicating efforts to destroy it -- makes mobility a problem for arms controllers. What is difficult to locate for targeting is also difficult to find for counting.

What is more, all things are not equal. The Soviet Union is not only larger than the US, but Soviet provincial leaders and environmental groups (to the extent the latter even exist) can hardly be expected to pose much resistance to Soviet military planners who want to move their missiles in the USSR. Our own Air Force (as the attempt to find a home for the MX clearly showed) is unlikely to encounter much enthusiasm for deploying Midgetman -- and then only in someone else's state.

With more space to hide in, Soviet missiles would in principle be harder to find. In addition, the Soviets' record of complying with arms control agreements suggests they may not be above stretching the numbers beyond what is strictly allowed; this is something we neither could nor would do. As a result we could find ourselves facing considerably more mobile missiles moving about than we had anticipated.

Serious as they are, these arguments do not settle the issue. The key concern of the US ought to be stability. For years we have recognized that the strategic forces that are more difficult to destroy, such as submarines and bombers, promote stability. No would-be attacker could be confident of striking first and neutralizing all or even most of our retaliatory capability; as a result, he is unlikely to strike first.

Mobility would give to land-based missiles, currently a weak link in our chain of deterrence, the critical attribute of reduced vulnerability. True, mobility would complicate the task of verifying any arms control agreement. Yet the potential adverse impact of increased uncertainly must be weighed against the increased benefits of greater survivability. Verification is a good thing, but it is not the only thing. Some margin of error could be worth accepting if the payoff were enhanced stability.

It might be possible to reduce the scope for uncertainty. One can imagine an agreement under which each side would deploy its allotted mobile missiles only in a designated area or ``reservation'' sufficiently large to produce the benefits of mobile deployment but not so vast as to frustrate all attempts at verification. Another approach would require exploring with the Soviets the idea of facilitating counting by adding specific cooperative measures to existing technical means of verification, such as s atellites. Establishing such special procedures at designated entry and exit points adjacent to the reservation would reduce the margin for error. The challenges are difficult but not necessarily beyond solution.

A more important possible limitation, which would reduce the significance of any uncertainty while promoting stability, would be to allow only single-warhead mobile ICBMs. This has the virtue of asking the USSR to forego deployment of a missile they have yet to add to their inventory, while permitting us to proceed with Midgetman. Unlike a total ban on mobile missiles, this approach has some chance of being negotiated. The USSR is too committed to mobiles to give them up entirely.

We can increase the Soviets' incentive to negotiate by reminding them that multiple-warhead missiles, by exacerbating the vulnerability of land-based missiles, strengthen the case for Reagan's SDI. This approach has the virtue of reducing the significance of miscounting or noncompliance: Even more than a few extra single-warhead missiles would not have the potential to threaten deterrence. Lastly, banning only multiple-warhead mobiles would have the virtue of enhancing stability: US missiles would be le ss vulnerable due to mobility, and a reduced threat would exist since Soviet mobile missiles would have only single warheads.

If, in a world of roughly equivalent inventories, it makes little strategic sense to use one missile to destroy one missile, it makes even less sense to use one when the odds of destruction are poor. Such virtue ought to be rewarded; rethinking the proposed ban on all mobile ICBMs would make for a good start.

Richard Haass, formerly of the Departments of Defense and State, lectures at the Harvard University Kennedy School of Government.