The United States and the Soviet Union continue to move steadily into strategic postures and toward the adoption of related doctrines that interact with each other in such a way as to encourage rapid escalation rather than deliberate response. Presidential Directive 59 appears to be more than just another milestone in this evolution, incorporating, among other things, an important, previously unannounced and highly inflammatory threat to attack the Soviet command and control. But the root issue lies deeper than PD59, in a fundamental choice for U.S. (and Soviet) strategic planning: whether to move forward or back in maintaining land-based missiles.

At bottom, there are two general paths open to the U.S. Defense Department in response to the growing vulnerability of our 1,000 land-based Minuteman missiles. In the first course, we would redouble our effort to resist technological trends, in a strategy worthy of King Canute, in order to match Soviet maintenance of land-based missiles and Soviet threats against our missiles. Here the vulnerabilities of our land-based force are resolved by purchasing a new (MX) land-based missile force, but one whose improved security rests unreliably on deception in a deployment shell game.

The new land-based missile force were suddenly to be deemed, like the old, vulnerable to Soviet attack, more and more MX holes (and MX missiles) would be constructed -- an expensive proposition in which good money is thrown after bad.

When and if this failed, an anti-ballistic missile system would be built to protect the MX missiles. (This would require amending the ABM treaty, thereby risking the destruction of an agreement that has saved both the United States and the Soviet Union untold tens of billions of dollars in useless expenditures.)

And if this ABM solution were to seem infeasible, the missiles would be prepared to "launch on warning" (i.e., to launch on the 20-minute warning of enemy attack); this is a cheap but absurdly dangerous fix, as recent computer failures have shown. (Nevertheless, it is already part of U.S. doctrine that we might fire on warning).

There is another path that accepts the inevitability of land-based missile vulnerability but "finesses" the Soviet attack. This strategy would put less -- rather than more -- emphasis on land-based missiles. We could keep Minuteman missiles (which are only about 25 percent of our strategic force) as a waning asset, or phase them down. We would make whatever compensating adjustments might be desired in our bomber and sea-based forces. The finessing path tends to move a major part of America's deterrent, and hence America itself, out of the line of fire of limited war.

This choice between the two paths has important implications for firing doctrines and hence for the overall likelihood of war. If one side has vulnerable missile forces, it has a defensive motivation to fire them more quickly ("use them or lose them"). And to the extent that the other side possesses vulnerable land-based missiles, one has also an offensive motivation ("time-urgent targets"). Worst of all, if both sides find themselves with vulnerable missile forces, both would have both motivations, and a cycle of reciprocating expectations ("better first than second") would increase the likelihood of preemptive escalation. Some catalytic outbreak of violence in Europe or wherever might then bring down the roof.

The finessing path would leave the Soviet land-based missiles (which are 70 percent of their force) vulnerable, in time, to our sea-based force. But since the reverse would not be true, the corresponding cycle of expectations would not exist. Thus, in fact, the path of finessing the Soviet threat leaves the Soviets trumped. More important, it depresses the likelihood of wars nobody wants by diminishing first-strike incentives.

The Defense Department fears that the path of finessing, and outmoding, the Soviet missile threat -- by removing U.S. land-based missile targets -- would seem a kind of acquiescence in coercion, even if compensating steps were taken with our other strategic forces, such as new kinds of sea-based forces. It argues also that some as-yet-unforeseeable future vulnerability of our sea-based deterrent in the 1990s might be importantly backstopped by land-based forces. But land-based force vulnerabilities (including those of MX) are already all too foreseeable to make this very plausible. Really, the choice appears to be one between inertia and agility.

The issues obviously go deeper than space here permits; unfortunately, no suitable forum really exists to decide issues of this magnitude. The situation cries out for a high-level commission, as proposed by Sen. Kennedy (and endorsed by both hawks and doves), that would consider U.S. strategic posture in the next two decades in the light of Afghanistan, SALT II, PD59, the very possible congressional defeat of the MX basing scheme, the growth of Soviet forces and all the rest.

With weapon systems taking 10 years to build and designed to function for 20 years beyond that, America can no longer afford to examine its defense posture only in the annual snapshots of congressional review. Now, while we are still at the fork in the road, would it not be wise to stop and think?