Not since the Cuban missile crisis 40 years ago has a high-stakes showdown between two nuclear-armed nations threatened to spiral until one miscalculation too many ends in a horrific nightmare of mushroom clouds.
Back then, the risk was global Armageddon. Today, the danger threatens millions -- perhaps tens of millions -- across the Indian subcontinent.
Both India and Pakistan insist a nuclear conflict would be only a last, desperate resort. But as Western countries urge their citizens to leave both countries, almost everyone agrees that escalating clashes between the two bitter rivals could spin out of control.
Strategic analysts believe New Delhi and Islamabad have painted themselves into a corner by vowing to respond to any attack.
"If war is thrust upon us, we would respond with full might," President Pervez Musharraf, Pakistan's military ruler, said this week as he and his senior officials explicitly refused to rule out nuclear retaliation to a conventional Indian strike.
Equally bellicose, Indian Prime Minister Atal Bihari Vajpayee urged his troops to prepare for "a decisive fight."
Teresita Schaffer, director of the South Asia Program at the Center for Strategic and International Studies in Washington, said it would be difficult now for either side to back down.
"An Indian military move would undoubtedly be calculated to minimize the risk of a Pakistani nuclear response," she said.
"The initial Pakistani response to such a move would also be limited but there would be a response. The danger lies in this tit-for-tat process, if both sides felt compelled to keep responding they would risk losing control of the escalation ladder."
With a vastly more powerful military, India would almost certainly win any all-out conventional war with Pakistan, as it has three times since the two countries were partitioned at independence in 1947.
A graver danger lies in whether Pakistan, especially a Pakistan under a military ruler, could accept the humiliation of a fourth defeat at the hands of its rival, now that it possesses nuclear weapons. Pakistan's nuclear doctrine is essentially the same as that of the North Atlantic Treaty Organization during the Cold War in that it refuses to rule out nuclear retaliation to a conventional attack.
During their last full-scale war, in 1972, neither India nor Pakistan had developed a weapon of mass destruction. Since then, both nations have also developed missile technology to deliver warheads hundreds of kilometres into each other's territory.
The two nations now have more than a million troops -- most of them Indian -- on a war footing on both sides of the mountainous "line of control" that divides Kashmir. But the greater concern to India are thousands of militants that since the 1980s have waged a guerrilla war against Indian forces from secure bases inside Pakistani territory.
Even if Mr. Musharraf were able to stop the cross-frontier infiltration by the militants, as the West this week demanded he do, there remains a real risk of further terrorist strikes from separatist militants inside Indian-controlled Kashmir.
That, warned Ms. Schaffer, could force New Delhi to launch a limited air strike against suspected militant bases in Pakistan. Indian officials said yesterday they believed militants were amassing in the mountain towns of Gilgit and Skardu, which are both on Pakistan's side of Kashmir.
But she doubted India would want to wage such a strike on Pakistani soil while the world was watching and calling for restraint.
"We can probably sleep easy over the weekend, unless there is another terrorist attack," she said yesterday in an interview.
Getting India and Pakistan to step back from the brink has eclipsed both the Palestinian-Israeli conflict and America's war on international terrorism. Russian President Vladimir Putin may try and broker a face-to-face meeting between Mr. Vajpayee and Gen. Musharraf next week, although both South Asian nations said yesterday they were not prepared for direct talks.
But even if conflict is averted, the long-festering Kashmir dispute will continue to bedevil relations between Pakistan and India, with no negotiated settlement in sight.
The conflict began with Britain's bungled partition of the subcontinent in 1947, when Kashmir's maharajah Hari Singh refused to accede to either of the new nations. A Hindu, Mr. Singh was personally attached to India and its first ruler, Jawaharlal Nehru, a Kashmiri himself by birth. But most of Mr. Singh's subjects were Muslim, and his territory would be the only one in a new India with a Muslim majority.
As the maharajah dithered over the decision, militiamen from Pakistan marched into Kashmir, attempting to liberate it from Hindu rule. Mr. Nehru dispatched the Indian army to fend off the infiltrators, on the condition the maharajah sign over his territory to India.
Kashmir has been divided ever since, with about two-thirds of its mountainous territory in Indian hands. And the one condition set by the maharajah for his loyalty to India -- that his decision be subjected to the will of the Kashmiri people -- has yet to be met by India.
India and Pakistan fought again over Kashmir in 1965, when Pakistani forces tried to invade the territory only to meet a humiliating defeat. They also engaged in an intense battle in 1999, near the high mountain town of Kargil.
But for most of the past 55 years, the two sides have shown restraint when it comes to their standoff. Since a Kashmiri uprising began in 1989, Pakistan's most controversial moves have been to support various militant groups with arms, training and diplomatic support. India's greatest offences, on the other hand, have been against the Kashmiri people, in the form of a brutal military occupation of much of the scenic mountain territory.
But through wars and violent times of peace, neither side has yielded in its claim to Kashmir.
Many Kashmiris -- perhaps most -- would prefer the two nuclear powers leave them alone, by granting the state independence. But when the British left the subcontinent in 1947, that was the one option it said the Kashmiris could not have.