Two nightmares stir nuclear strategists. One is to be intimidated, if not attacked, and the other is that in a crisis one side, feeling its forces were vulnerable, might fire first to avoid being hit first. The "intimidationists'" nightmare is what drives Ronald Reagan's comprehensive new strategic program. The open question is whether he has taken the "first strikers'" nightmare into adequate account.

The perils of a first-strike world, a world not created but made more real by the Reagan program, are familiar to strategists. But they have been half-ignored in the MX debate. The vulnerability of the MX to surprise attack has been widely noted but not that the MX is intended in part, in time, for a surprise attack on Soviet missiles.

Think about that. The goal in basing the MX is to find a way to nullify an expected Soviet capacity to take out our land-based missiles. But one goal in deploying the MX is to give the United States a like first-strike capability. And if the MX cannot be made survivable, we still will have the first-strike D5 missile at sea.

A couple of questions:

1)Is this fair and equal? No, but what we should want is not to be fair but to be secure.

2)Is it secure? No. If we can look past the American "window of vulnerability" Reagan is trying to close, we will see a Soviet "window of vulnerability" he is trying to open.

At least theoretically, Soviet land-based missiles will in some measure be vulnerable toward the end of the 1980s. Particularly is this so since Moscow has a larger part of its missiles based on land than we do and, lacking our naval tradition and our free ocean access, it cannot so easily move missiles to sea.

Some people are troubled by the Reagan MX plan for fear it won't work. I am troubled for fear it will work. To the extent that it does, the Soviet missile force goes on a hair trigger.

This also helps explain why the Soviets are more interested than we in SALT II. SALT has special value as an instrument to limit the threat to land-based missiles, and the Soviets have many more of their strategic eggs in the land-based basket.

That leaves the question of why both sides have gone for a first-strike capability.

Perhaps the Soviets are being aggressive. They may also be stupid, blinded by technological hubris. For their targeting of our silos has pushed us into accelerating the movement of our forces to invulnerability (in subs, cruise missiles, etc.) and into threatening their silos (MX, D5, etc.).

To make the Soviets spread their effort and thus to weaken their threat is one reason we are targeting their silos. But are we not also encouraging a Soviet tendency to impute to us first-strike designs? Is there not a certain technological momentum on the American side, too?

Our stated purpose in aiming new weapons at Soviet missiles is to match or "offset" the Soviets' similar capability. This shows our determination not to be intimidated. Fortunately, that's not all. Our targeting of Soviet missiles tightens the pressure on Moscow to put its missiles to sea or otherwise make them more survivable.

In short, we are at another turning point. The worst that might happen is for the great powers to become mired in the first-strike world that both seem intent on entering despite its awesome mutual dangers.

The best perhaps is that President Reagan, having deployed his first MX missiles in temporary quarters, will find that his search for permanent quarters comes to a dead end. That could make MX merely the price we must pay to end our unwise strategic and psychological reliance on vulnerable land-based missiles, and to influence the Soviets as well as ourselves to shift deterrence to sea.

We would both then have forces more nearly symmetrical: unbelievably destructive but relatively matched in the gross numbers and fairly invulnerable. That's the important thing: It really doesn't matter whose force is set on a hair trigger. It's equally risky to both sides.