As one would expect, coverage of Robert McNamara's death has focused on his management of the Vietnam war and his later reappraisal of its necessity, but the former secretary of defense left an equally important--and far more positive--legacy regarding U.S. nuclear policy.
When McNamara joined the Kennedy administration in 1961, American nuclear "strategy" called for launching the entire nuclear arsenal--nearly 3,500 weapons--at the communist bloc if the Soviets made any move against Western Europe. This approach had severe flaws. For one thing, it meant that the United States would kill hundreds of millions of civilians. Indeed, it would decimate nations, like China, that were unlikely to even be involved in a Soviet attack. What's more, such an attack would leave the United States open to nuclear retaliation. After all, there was little chance that our first strike would destroy every Soviet weapon, and even a modest number of warheads could take out most major American cities.
McNamara, understandably, wanted an alternative, and initially he settled upon a strategy known as "counterforce." In the event of a Soviet attack on Western Europe, counterforce dictated that the United States would first target Soviet military forces. The strike need not be an all-out "war orgasm," as Herman Kahn memorably put it. Rather, the idea would be to stop the conventional assault and degrade the Soviet ability to retaliate. We would keep some nuclear weapons in reserve and hold Soviet cities hostage to a second strike to deter them from responding in kind. In essence, we would treat nukes much like regular weapons. As McNamara said on June 17, 1962, "[Our] principal military objectives, in the event of a nuclear war stemming from a major attack on the Alliance, should be the destruction of an enemy's forces, not his civilian population." The implication, as I noted in U.S. vs. Them, was that, like a conventional war, a nuclear war might be winnable.
But McNamara soon realized that, although it might be better to have options besides launching a total nuclear holocaust, counterforce would not meaningfully limit damage to the United States in the event of a nuclear conflict. It took only a few enemy weapons to stop the United States from functioning as a society; we wouldn't be able to take out all the Soviet weapons in a first strike; and if we used nukes, the Soviets were unlikely to resist their impulse to retaliate. Combined with studies showing that it was impossible to effectively defend against a nuclear attack-either by shooting down incoming missiles and bombers, or by sheltering civilians from radiation-that logic forced McNamara to conclude that the United States would never benefit from using nuclear weapons against a nuclear-armed adversary. Doing so would be suicidal.
So in September 1967, McNamara gave a speech that emphasized deterrence through the ability to inflict "unacceptable damage" on the enemy even after a surprise first strike. He called this an "assured-destruction" capability. McNamara's conversion by no means resolved debates over U.S. nuclear posture. Conservatives never accepted the vulnerability imposed by mutual assured destruction, which they parodied with the acronym "MAD." They fought for missile defense, fallout shelters, and war-fighting strategies. Democrats and Republicans alike constantly worried whether the Soviets might eke out some nuclear advantage. And the United States continued to target Soviet nuclear forces because, in the event of a nuclear war, one might as well try to win. But McNamara had long ago realized the impossibility of victory. Mutual assured destruction was not a policy that American officials could accept or reject; it was an inescapable condition of large nuclear arsenals. The best that policymakers could do--indeed, the responsibility they had--was to manage that condition so that it did not lead to war.
In his later years, McNamara advocated efforts toward nuclear disarmament, and he strongly criticized George W. Bush's flaccid efforts at arms control and his plans to build new, bunker-busting nuclear weapons. Such positions put him in the company of other high-level nuclear skeptics not known for their dovishness, like Paul Nitze and, more recently, George Shultz, Henry Kissinger, Bill Perry, and Sam Nunn. They also put him in line with Barack Obama's vision of a world without nuclear weapons and his agreement yesterday with President Medvedev to further reduce the U.S. and Russian arsenals. But none of those efforts would be possible were it not for the realization, officially articulated by McNamara, that a nuclear war cannot be won and must therefore never be fought.