THE STATE Department's advisory to Americans to leave India suggests the administration is finally taking seriously the first nuclear confrontation since the Cuban missile crisis nearly 40 years ago.
Until now, Washington seemed more annoyed than alarmed at what was developing between India and Pakistan, as if it were an unwanted diversion from the more important work of chasing al-Qaida terrorists through the mountains in Afghanistan bordering Pakistan or planning war against Iraq.
Apparently somebody (probably the Pakistanis, with their provocative missile test) tripped a wake-up alarm in the White House or State Department and forced this vital refocusing.
There's irony in this, following as it does the signing of a treaty by President Bush and Russian President Vladimir Putin under which both countries promise to put thousands of nuclear weapons out of commission. An observer close to the treaty negotiations described it as the final nail in the coffin of the Cold War. I took that with a mix of relief and nostalgia.
Relief is an understandable response from anyone who lived through the Cold War -- that era of duck-and-cover and backyard bomb shelters, when words like "megadeath" were added to our language and the images it evoked flowered like black lilies in the mind.
The nostalgia flows from a recollection of the positive elements of that half-century standoff between the two superpowers, then more or less evenly balanced. This stalemate provided certain reassurances that may or may not be on offer today: First, both sides realized that to shoot first was suicide; second, in those years, the superpowers rigorously policed their nuclear arsenals.
Nukes made the world a different place. They changed the rules of international relations, the nature of warfare. Nukes are different because they are unchallengeable.
No effective system of defense has been invented against the nuke, as was the case with virtually all other weapons. The portable shield deflected the spear and arrow, the tank blunted the machine gun's power, the sonar, depth charge and fast destroyer neutralized the submarine.
Against nukes there is no defense. They are too big for the planet. And since those relatively small bombs dropped on Japan to end World War II, they have gotten bigger. That deadly evolution in size and destructive power brought into being a strategic situation nobody had counted on.
Back then, those who got paid to think about such things, who wrote the language for the nuclear debate, eventually tortured this situation into a veritable doctrine, a theory for those times. They gave it the unlovely name mutual assured destruction, or MAD.
The film director Stanley Kubrick may not have been the first to appreciate the ironic quality of MAD, but he was probably the first to exploit the dark humor in it. In his 1964 movie Dr. Strangelove, he showed us all that what the Soviets and Americans had brought into being by their ceaseless accumulation of nukes was a doomsday machine, an uncomplicated mechanism equipped with a single, fateful toggle: It would save us, or kill us.
Though it provided certain comforts, one shouldn't think of the MAD period as one of serenity. On the contrary, the zeitgeist of the time was fear -- always fear, always there.
This fear propelled an unceasing and futile struggle by each country to get ahead of the other. In the 1960s, for instance, each superpower possessed several hundred deliverable nuclear weapons, enough, it was thought, to deter the other. But neither would accept this status quo.
When the Soviet Union dissolved a decade ago, each country possessed more than 10,000 nuclear warheads, more than could ever be used. Each weapon added to the pile, following the logic of MAD, made the use of any one of them slightly less likely. How strange.
India and Pakistan, which have fought three wars, are currently lobbing conventional artillery shells across their common border in Kashmir. The death toll rises. A major battle could progress to all-out conventional war, and on until the nuclear-tipped missiles are sent flying.
If reason prevails on the subcontinent, it will in all likelihood be owing to the same dynamic of fear that got us through the confrontation over Cuba and kept the nuclear-armed missiles confined to their silos for decades across the American and Russian heartlands: Fear -- fear of burned cities, of epidemics of radiation sickness, of the choking darkness of a nuclear winter, the ultimate doomsday blowback.
All we can do, then, is hope the doomsday machine still works.
Richard O'Mara is a former foreign editor of The Sun.