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Retrospectives on MIRVing in the First Nuclear Age

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Why did the Nixon Administration open the floodgates to MIRVs when it was clear that the Kremlin would follow suit, effectively ruining prospects for serious strategic arms limitation?

Domestic politics had something to do with this result, because President Richard Nixon and national security advisor Henry Kissinger couldn’t cross the Pentagon and its supporters on Capitol Hill by quashing MIRVs. But the Nixon/Kissinger team offended Hawks on other issues, such as opening diplomatic relations with “Red” China and giving up on nationwide ballistic missile defenses. Ergo, domestic politics mattered, but weren’t the overriding reason to MIRV.

Verification concerns also played a part in the decision to let MIRVs run free, but they were hardly decisive. A ban on further flight-testing of multiple re-entry vehicles would have been politically taxing, but feasible from a monitoring perspective without requiring on-site inspections. The Arms Control and Disarmament Agency’s blue ribbon General Advisory Committee, Chaired by the redoubtable John J. McCloy, advised the Nixon Administration to this effect. (Extraordinary primary documents on this and other SALT matters can be found in the Digital National Security Archive, U.S. Nuclear History, 1969-1976: Weapons, Arms Control, and War Plans in an Age of Strategic Parity.) Verification difficulty wasn’t the driver here; freedom of action was. Hard-liners in Washington and Moscow deemed MIRVs to be necessary; the dance of the veils they carefully choreographed was purposefully designed to avoid negotiating a ban on MIRVs.

A half-hearted reason for letting MIRVs run free was to secure bargaining leverage for subsequent negotiations, but this was a risible excuse. The worrisome ramifications of MIRVs could be easily foreseen and, besides, Washington and Moscow didn’t cash in bargaining chips during the Strategic Arms Limitation Talks. Bargaining chips only became expendable fifteen years after the SALT I Interim Agreement’s allowance of MIRVs, when Ronald Reagan and Mikhail Gorbachev were willing to trash orthodoxy in nuclear deterrence and targeting.

Technological drivers explain the timing of MIRVs, and competing laboratories – domestic as well as foreign – help explain the procession of warhead designs that followed. But technological determinism and vested domestic interests are not persuasive in explaining the resulting profusion of warhead totals, propelled by MIRVs, boosting superpower arsenals past the 10,000 mark.

So what were the prime movers behind MIRVs in the United States? Two stand out: the Soviet challenge and the embrace of counterforce targeting. The result of these interlocking drivers kicked the superpower competition into overdrive. Secretary of Defense Robert McNamara and arms controllers opposed to ballistic missile defenses assumed that the “action-reaction” phenomena would be propelled by parallel offensive and defensive moves. But the propulsive effect of MIRVs was so great that the superpower arms race didn’t skip a beat even when national missile defenses were foreclosed by the Anti-Ballistic Missile Treaty.

Retrospective laments about MIRVs by those who enabled their prevalence were lacking in candor. The most memorable was voiced by Henry Kissinger in a press backgrounder after negotiating a tentative follow-on agreement to the SALT I Interim Agreement at Vladivostok in 1974: “I would say in retrospect that I wish I had thought through the implications of a MIRVed world more thoughtfully in 1969 and 1970 than I did.” The best Kissinger could do in the two year interval after SALT I was to top off MIRVing at 1,320 land- and sea-based strategic nuclear delivery vehicles. Even this was deemed to be unacceptable by Hawks in the Ford Administration and on Capitol Hill.

In truth, Kissinger and every other key participant in the fateful decision not to seek a ban on MIRVs in SALT I knew full well what the consequences would be: a large increase in warhead numbers, concerns about land-based missile vulnerability, and an acceleration of the strategic arms race. The Vladivostok Agreement clarified the obvious and predictable strategic consequences of failing to ban MIRVs.

Nixon and Kissinger factored in the risks of letting MIRVs run free and found this to be acceptable – or at least more acceptable than not proceeding with MIRVs. As Melvin Laird, Nixon’s Secretary of Defense, later wrote in an essay published byInternational Security in 1985,

“MIRVs were a relatively low-cost means for modernizing our strategic missiles in the near term. They would provide us with a larger number of surviving warheads in the event of a first strike and, in addition, a needed hedge against the ABM system the Soviets were deploying, without requiring us to embark on a costly expansion of our missile forces. In short, MIRVs were the only feasible option available for response to an expanding Soviet threat, given the hostile attitude of many members of Congress toward defense spending.”

MIRVs were not just cost-effective counters to BMD, they were also cost-effective counters to Soviet missile modernization programs. Removing the first rationale didn’t diminish requirements for the second. As Henry Kissinger wrote in White House Years (1979), MIRVs were “crucial” and “our counterweight to the growing Soviet numbers.” New Soviet missiles were coming off production lines at a rate of 200-300 per year during the SALT I negotiations. Without MIRVs, the Nixon White House believed that the United States would have been out-competed by the Kremlin, badly undermining US security while damaging US international standing and alliance management.

The proliferation of MIRVs and the advent of prompt hard-target-kill capabilities were inseparable drivers. Their combined effect significantly altered and undermined calculations of strategic stability. MIRVs meant that second-strike, retaliatory capabilities would grow significantly, but this was scant comfort, because first-strike capabilities also would grow precipitously. The superpower competition rose to new heights with vastly expanded targeting lists.

MIRVs were a signature feature of the first nuclear age, figuring prominently in the death of SALT. As William Hyland, a close confidant of Kissinger, wrote in Mortal Rivals (1987),

“Refusal to ban MIRVs was the key decision in the entire history of SALT I. Both Nixon and Kissinger thought it would be a weak move at the outset of a new administration and the opening of a long negotiation. And it would have provoked a bloody fight inside the administration and in the Congress. It was a truly fateful decision that changed strategic relations, and changed them to the detriment of American security. But I doubt that Nixon and Kissinger could have forced through the Pentagon both a ban on MIRVs and a sharp limit on ABMs, and then persuaded the Soviets to agree.”

(Continued from here.)

Michael Krepon is Co-Founder of the Stimson Center. This piece originally ran in Arms Control Wonk on April 5, 2016.

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