A Choice of Arms

By BRUCE VAN VOORST

It could be the most momentous national-security decision that George Bush ever makes. In early April the President must choose a multibillion-dollar plan for modernizing the nation's land-based intercontinental ballistic missiles. Though dozens of basing modes and several new missiles have been considered, only two expensive mobile missile systems are really in the running: the rail-carried, multiwarhead MX and the truck-transported, single- warhead Midgetman. Bush's wisest course might be to deploy neither one.

The President's deliberations will be guided by the concept that has been the basis of U.S. nuclear deterrence for more than 30 years: that enough American weapons must survive a Soviet surprise attack to guarantee a devastating retaliatory strike. Pursuing that strategy, the U.S. has built a formidable triad of strategic nuclear forces: land-based ICBMs in silos, sea- based missiles aboard submarines, and nuclear bombs carried by airplanes. But over the years, the increased accuracy of Soviet ICBMs has gradually threatened the land-based leg of the triad, which consists of 450 Minuteman IIs, each carrying a single warhead; 500 Minuteman IIIs tipped with three warheads; and 50 more modern MX's, each with ten warheads. The Administrations of Gerald Ford, Jimmy Carter and Ronald Reagan considered 30 or so ideas for rendering U.S. ICBMs less vulnerable to Soviet attack. But as a report co- authored by former Defense Secretary Harold Brown noted, all the proposals were rejected because they failed the basic criteria of being "militarily effective, affordable and politically acceptable."

As Bush makes up his mind, skeptical strategic experts are challenging the fundamental assumption: that land-based missiles are as vulnerable as some other experts fear. There is considerable doubt that the Soviets could actually attack U.S. ICBMs with impunity. Studies by the Pentagon suggest that even if the Soviets aimed two warheads at each U.S. silo, they could count on destroying only 65% to 80% of the ICBMs. That would leave at least 400 land- based U.S. warheads -- each packing about 20 times the destructive force of the Hiroshima bomb -- for a counterattack on the Soviet Union. Moreover, the Soviets would always have to fear that the U.S., alerted to a surprise attack, would simply launch its entire force before enemy missiles arrived. Says conservative strategist Fred Ikle: "The Soviets can never have a high confidence of destroying these missiles in their silos."

Although many respected observers argue the case, it makes little sense to worry unduly about the vulnerability of the land-based leg of the triad when it accounts for only 20% of the 12,000 warheads in America's strategic nuclear arsenal. Even in the unlikely event that a first strike wiped out the entire American land-based missile force, the U.S. could still obliterate the Soviet % Union with a fraction of the 5,300 warheads on its modern missile submarines and the 4,700 on its bombers. Though the first operational test last week of a Trident II missile resulted in a spectacular pinwheeling explosion, that failure was at worst a temporary setback for a weapon that will give the U.S. a sea-based silo-killing capability for the first time. In fact, it is the Soviet Union, not the U.S., that has a real problem with the survivability of its nuclear forces, since as many as 55% of its warheads are concentrated in vulnerable land-based silos. That explains why Moscow has developed the rail- mobile SS-24, which carries ten warheads, and the truck-carried SS-25 single-warhead missile.

Logic, unfortunately, does not always dictate strategic decisions. Irrational as the fear of a Soviet surprise attack may be, psychological and political reasons alone may push the the U.S. into proceeding with a new mobile missile. As one congressional expert put it, "You can't debate survivability for a decade and then not do anything." It is unlikely that the Senate would ratify a Strategic Arms Reduction Treaty that allowed the Soviets mobile missiles unless the U.S. first decided to acquire a comparable system.

The critical question thus becomes which of the missiles to buy. The ten- warhead MX, which Reagan dubbed the Peacekeeper, is a proven, highly accurate ICBM. In one option, the 50 MX's already deployed in ICBM silos would be supplemented by another 50 "garrisoned" on special railroad cars stationed on military bases. If a U.S.-Soviet confrontation loomed, the missiles would be moved out on 180,000 miles of railway across the nation. The main advantage of this scheme is its relatively low price tag: an estimated $12 billion for 50 missiles carrying 500 warheads. A somewhat cheaper option ($8 billion) would shift the existing silo-based MX's to railroad flatcars.

The single-warhead Midgetman (a misnomer for a missile weighing 37,000 lbs.) would sidestep the vulnerability problem by being deployed on hardened, tractor-drawn launchers. In times of crisis, the launchers could be dispersed over thousands of square miles on and off military reservations. But while military planners consider the Midgetman more survivable in a surprise attack than the MX, it is much more expensive: $39 billion for 500 missiles carrying 500 warheads.

The choice between the two missiles must take into account the projected overall ceiling of 4,900 land- and sea-based ballistic-missile warheads that has been set in the START negotiations. With smaller numbers of warheads on both sides, there is a strategic advantage in single-warhead missiles like Midgetman. By dispersing its quota of warheads on a larger number of Midgetman missiles instead of concentrating it on a smaller number of MX's, the U.S. could greatly complicate a Soviet first strike.

Such logic argues powerfully for the Midgetman if and when the U.S. modernizes its ICBM force. But the odds are that the Administration will propose building at least some of both new missiles. Bush will argue that the MX is a tested weapon that can be speedily deployed on railcars to deal with the problem of vulnerability. But given strong Democratic support for the Midgetman, he will have to accept that system as well.

Congress is likely to go along with the compromise, though a heated debate over numbers and timing will ensue. The controversy will involve claims that deploying the new missiles so diminishes the threat of a surprise Soviet attack that the Strategic Defense Initiative is unnecessary. Some SDI supporters will argue for delaying new missile deployment in the expectation of major breakthroughs in Star Wars.

In the rush to judgment, both the President and Congress are missing an opportunity to trump Soviet leader Mikhail Gorbachev's arms-control ideas. Soviet multiwarhead SS-18s pose the principal threat to American ICBMs. It might be easier to reduce the threat by negotiating further cutbacks in Soviet missiles than by building new U.S. weapons. Under START, SS-18s would be cut 50%. Still more reductions could be sought in return for a U.S. agreement to refrain from deploying more MX's. Efforts could also be made to dissuade the Soviets from further deployment and upgrading of their ten-warhead SS-24, possibly in exchange for a U.S. offer to hold off on the Midgetman or cut back on silo MX's. While these ideas are being explored, strategic decisions should be based on the same maxim that is supposed to guide physicians: "First, do no harm."

Opting for both Midgetman and rail MX would be the worst possible resolution of an ICBM survivability problem that may not exist. For the U.S., there may be more to gain through imaginative negotiating than from forging ahead with new ICBMs.

CHART: NOT AVAILABLE

CREDIT: TIME CHART BY CYNTHIA DAVIS

CAPTION: The administration must decide whether to replace the existing arsenal of Minuteman missiles with the MX or the Midgetman or both