Obama's hunger for a diplomatic success, such as it is, allowed the Russians to exact a price: linkage between offensive and defensive nuclear weapons. This is important for Russia because of the huge American technological advantage in defensive weaponry. We can reliably shoot down an intercontinental ballistic missile. They cannot. And since defensive weaponry will be the decisive strategic factor of the 21st century, Russia has striven mightily for a quarter-century to halt its development.

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.